Direct Answer
A flat bottom pouch — also called an eight-side seal bag, box pouch, or block bottom bag — is a flexible pouch built with a rigid rectangular base panel and two side gussets, giving it five printable panels instead of the two or three found on a standard stand-up pouch. The format is chosen when a brand needs the pouch to stand straighter on shelf, carry more branding area, and hold heavier fills than a bottom-gusset stand-up pouch of the same footprint.
If your product is coffee, tea, nuts, dried fruit, pet food, protein powder, or a premium dry good above roughly 250 g and shelf presentation is part of how the product competes, a flat bottom pouch is usually the format to test first. If your product is liquid, paste, or a low-margin bulk commodity sold mainly online, a stand-up pouch or spouted pouch is normally the better commercial fit.
Terminology note: in the flexible packaging industry, flat bottom pouch, eight-side seal bag, 8-side seal pouch, box pouch, and block bottom bag all describe the same structure. Chinese suppliers frequently quote "八边封袋" (eight-side seal bag) for exactly what Western suppliers call a flat bottom pouch. If you are comparing quotes between a Chinese factory and a Western distributor, confirm you are pricing the same construction before comparing unit cost.
What Is a Flat Bottom Pouch?
A flat bottom pouch is a three-dimensional flexible pouch in which the bottom is formed as a separate flat panel that is heat-sealed to the front, back, and both side gussets. When filled, the pouch resolves into a roughly rectangular prism — closer to a soft carton than to a traditional bag.
The "eight-side seal" name comes from the number of distinct heat-seal lines in the construction. Where a three-side seal bag has three seals and a plain stand-up pouch typically has a top seal, a bottom seal, and two side seals, the flat bottom construction adds seal lines where the flat base panel meets the side gussets and front/back panels. In practice the count varies by converter and bag design, so treat "eight seals" as a structural description rather than a fixed number you can verify on a drawing. What matters to a buyer is the resulting geometry, not the seal count.
The five panels — and why they matter commercially
The structure produces five usable surfaces:
- Front panel — hero branding, product name, net weight
- Back panel — ingredients, nutritional data, barcode, regulatory text
- Left side gusset — certifications, origin story, usage instructions
- Right side gusset — secondary messaging, QR code, sustainability marks
- Bottom panel — surprisingly valuable: when the pouch sits on a shelf at eye level, the bottom face is visible from a low angle and can carry a barcode or campaign message
For brands moving from a two-panel stand-up pouch, the practical effect is that compliance text, certification logos, and marketing copy stop competing for the same real estate. This is often the real reason brands switch — not aesthetics.
Flat Bottom Pouch vs Stand-Up Pouch vs Side Gusset Bag
These three formats are frequently quoted interchangeably by suppliers, which causes avoidable specification errors. The differences below are structural and consistent across the industry.
| Selection factor | Flat bottom pouch (eight-side seal) | Stand-up pouch (doypack) | Side gusset bag |
|---|---|---|---|
| Base structure | Rigid flat rectangular base panel | Bottom gusset that folds open | No self-standing base |
| Printable panels | Five | Two to three | Front, back, two gussets (no visible base) |
| Shelf stability when filled | Highest — weight distributes across a flat base | Good, but depends more on fill weight and product shape | Poor without external support |
| Typical fill range | Wider range upward; commonly used from a few hundred grams to several kilograms | A broad range, often favoured for small to medium fills | Often used for larger bulk coffee and dry goods |
| Material usage per unit | Higher — more film and more converting steps | Lower | Moderate |
| Unit cost tendency | Usually the highest of the three | Usually the most economical | Moderate |
| Suitability for liquids | Generally poor — gusset corners are a stress point under hydrostatic load | Good, especially with a spout | Poor |
| Machine compatibility | Premade-pouch lines (HFFS); generally not produced inline on VFFS | Premade-pouch lines and some VFFS | Premade-pouch lines and VFFS |
| Storage before filling | More bulky than a flat pouch, still far more compact than rigid packaging | Compact | Compact |
The single most useful takeaway from this table: the barrier performance of all three formats is driven by the film structure, not by the pouch shape. A well-specified stand-up pouch will outperform a poorly specified flat bottom pouch on oxygen and moisture protection. Choose the format for presentation, capacity, and filling-line fit — then choose the material for shelf life.
When a Flat Bottom Pouch Is the Right Choice
Specify a flat bottom pouch when most of the following are true:
- Shelf presence drives purchase. Your category is crowded and the pack has to read cleanly from two or three metres away.
- Fill weight is at or above roughly 250 g. This is the point where base stability starts to matter visibly in retail display.
- The product is premium-positioned. The format supports a higher retail price because it reads as more structured and more considered than a soft pouch.
- You need five surfaces. Certification marks, multilingual legal text, and marketing copy cannot all fit on two panels.
- You pack on a premade-pouch machine. Flat bottom pouches are designed to be supplied finished and run on HFFS or premade-pouch lines.
- You want to reduce or remove outer cartons. A pouch that stands firmly on its own can sometimes replace a display carton — a genuine cost offset against the higher unit price.
Applications where the format is well established
- Coffee — roasted beans and ground. Often combined with a one-way degassing valve and a resealable zipper. See our custom coffee bags with valve and block bottom coffee bag.
- Tea — loose leaf and premium blends. The structured base suits gift and retail positioning.
- Nuts, dried fruit, and trail mixes. Benefits from base stability and a broader display face. See our flat bottom pouch for nuts and dried fruit.
- Pet food and treats — particularly larger fill weights where tipping is a real risk.
- Protein powder and nutritional powders. Large front panel for claims, scoop information, and dosing guidance.
- Freeze-dried foods, cereal, and premium snacks.
- Non-food dry goods where a premium shelf look matters — for example detergent powders and chemical granules, such as our heavy-duty flat bottom bag for detergent. The structural logic is identical, but material and regulatory requirements differ substantially from food-contact packaging.
When a Flat Bottom Pouch Is the Wrong Choice
A competent supplier should tell you when the format does not fit. These are the cases where it usually does not:
- Liquids, sauces, and pastes. The gusset corners and multiple seal intersections concentrate stress under hydrostatic load, and flex-cracking can open pinholes in transit. Use a spouted pouch, a retort pouch, or a bottle instead. This is the most common specification error in this format.
- Very low fill weights. Below roughly 100 g the structural advantage largely disappears while the cost premium remains. A stand-up pouch or three-side seal sachet usually delivers better value.
- E-commerce-only brands with no retail shelf. If physical display never happens, you are paying for a benefit nobody sees. Stand-up pouches are often the better economic choice.
- Very low-margin bulk commodities. The format raises unit cost materially. It needs a retail price that can absorb it.
- Brands needing very small test runs. The converting process and printing setup favour higher volumes. Digital printing has lowered this barrier considerably, but flat bottom pouches still generally carry a higher practical minimum than simpler formats.
- Products requiring high-temperature retort sterilisation. Retort applications have their own film and seal requirements; confirm compatibility explicitly rather than assuming a standard flat bottom structure will survive the process.
Material Structures and Barrier Selection
The pouch shape is fixed by the die line. Shelf life is decided by the film. These are the structures most commonly specified for flat bottom pouches, with their practical trade-offs:
| Structure | Barrier tendency | Cost tendency | Recyclability | Typical use |
|---|---|---|---|---|
| PET/AL/PE (aluminium foil laminate) | Highest — foil blocks oxygen, moisture, and light | Highest | Not recyclable in most curbside systems | Oxygen-sensitive coffee, long-shelf-life dry goods |
| PET/VMPET/PE (metallised) | Medium to high; light-blocking, lower oxygen barrier than foil | Moderate | Limited | Coffee, snacks, nuts where foil is unnecessary |
| PET/PE | Moderate — moisture barrier more than oxygen barrier | Lower | Limited | Shorter-shelf-life dry foods, nuts, dried fruit |
| Kraft paper / PLA bio-film laminate | Moderate, with a strong natural look | Higher | Depends on the exact structure — verify, do not assume | Organic and eco-positioned coffee and dry goods — see our kraft and compostable PLA coffee pouch and mono-material recyclable packaging |
| Matte BOPP laminate | Moderate; chosen primarily for finish | Moderate | Limited | Premium matte-black coffee and specialty retail packs |
| Mono-material PE or PE/PE | Moderate; can be engineered upward | Moderate to higher | Designed for recyclability | Brands with explicit recycling commitments |
How to actually choose: start from target shelf life and the specific degradation mechanism, not from the material list. Coffee is mainly an oxygen and aroma problem. Nuts and dried fruit are mainly a moisture and rancidity problem. Powders are mainly a moisture and caking problem. Different problems require different barrier priorities, and paying for foil you do not need is one of the easiest ways to waste packaging budget.
Two practical points most buyers learn late:
- Ask for tested barrier data, not adjectives. A supplier should be able to provide oxygen transmission rate (OTR) and water vapour transmission rate (WVTR) figures for the proposed structure. If they cannot, the "high barrier" claim is unverified.
- Ask which layer faces the product. The product-contact sealant layer determines seal integrity and food-contact compliance. The outermost layer determines print quality and scuff resistance. These are separate decisions and should be specified separately.
Sizes and Fill Capacities
Flat bottom pouches are quoted as width × height + gusset, and the relationship between dimensions and fill weight is only approximate. The same nominal size from two suppliers will hold different amounts of the same product, because film thickness, seal width, gusset depth, and bag geometry all differ.
The table below is a published industry reference range compiled from publicly available supplier size charts. It is intended as a starting point for discussion with your converter — not as a specification, and not as a statement of what any particular factory stocks.
| Nominal fill | Commonly published reference dimensions (W × H + gusset) | Typical application |
|---|---|---|
| 250 g | Approx. 105–125 mm × 200–230 mm + 65–75 mm | Retail coffee, specialty tea, small snack packs |
| 500 g | Approx. 110–130 mm × 250–280 mm + 75–90 mm | Coffee, protein powder, nuts |
| 1 kg | Approx. 130–145 mm × 310–360 mm + 90–110 mm | Coffee, pet food, bulk dry goods |
| 2 kg and above | Approx. 200 mm × 380 mm + 120 mm and upward | Bulk pet food, wholesale dry goods |
Two caveats that matter more than the numbers:
- Volume, not weight, determines fit. Coffee is sold by weight but packed by volume. Whole beans need more physical space than ground coffee of the same weight because beans leave irregular air gaps. A pouch that fits 250 g of ground coffee comfortably may be tight for 250 g of whole beans.
- Test with your actual product before committing to a run. Fill a physical sample with your real product, seal it, and stand it on a shelf. This catches problems — overfilled seals, a bag that leans, a top panel that looks empty — that no dimension table can predict.
Closure and Functional Options
These add-ons change unit cost and lead time, and they must be specified before printing, because most are applied inline during converting.
- Resealable zipper. Press-to-close is the most common and most economical. Double-track and slider variants improve perceived quality and are easier for less dexterous users. Specify the zipper position — it affects usable fill height.
- One-way degassing valve. Effectively standard for freshly roasted coffee. It allows carbon dioxide to escape while restricting oxygen ingress. Valves are commonly supplied pre-fitted, and can also be supplied separately for brands that install them in-house. Position matters: the valve needs to sit above the fill line after sealing, so confirm placement against your fill weight.
- Tin tie. A fold-over closure common on kraft coffee pouches, valued for the artisan look.
- Tear notch. Low cost, measurable effect on consumer experience.
- Transparent or frosted window. Useful when the product itself is the selling point. It requires a window-patch step.
- Hang hole (Euro hole). For pegboard retail.
- Spout. Occasionally specified on flat bottom pouches, but note the liquid-compatibility limitation above — a spout does not turn a flat bottom pouch into a good liquid package.
- Surface finish. Gloss, matte, soft-touch, spot UV, and metallic effects are all achievable. Matte and soft-touch are typically chosen for premium positioning — see our matte black flat bottom coffee bag; and note that matte finishes can scuff more visibly in transit than gloss, which is a real trade-off if your packs travel unprotected in a carton.
Filling and Sealing Machine Compatibility
This is where flat bottom pouch projects most often go wrong, and it is worth raising with your supplier at quotation stage rather than after artwork approval.
- Premade-pouch lines are the intended route. Flat bottom pouches are normally supplied finished and run through horizontal form-fill-seal (HFFS) or dedicated premade-pouch machines.
- Vertical form-fill-seal (VFFS) generally cannot form this shape inline. If your line is VFFS-only, the realistic alternatives are to switch pouch format, change line, or run premade pouches on separate equipment. Establish this before you commit to tooling.
- Bag magazines and grippers must match gusset depth. The pouch's gusset depth and base panel width determine how it is picked and held. Send your machine make, model, and pouch-holder specification to your converter.
- Seal parameters need calibration. Seal temperature, dwell time, and pressure must be tuned to the specific film structure. This is not transferable between materials — moving from PET/PE to PET/AL/PE requires re-validation.
What Actually Drives the Unit Price
When flat bottom pouch quotes vary widely between suppliers, the gap is almost never "cheaper labour". It is normally one of these six variables. Ask which ones changed.
- Film structure. Moving from a two-layer to a foil-containing or metallised structure is usually the single largest cost change.
- Order quantity vs print method. Gravure printing has high setup cost per colour and rewards volume. Digital printing has much lower setup and suits smaller or multi-design runs — at a higher per-unit cost. This is why MOQ and print method are really one decision, not two.
- Number of colours. Each gravure colour adds a cylinder and setup. Design restraint has a direct price.
- Bag size and gusset depth. More film and a more complex die line.
- Functional add-ons. Zipper, valve, window, and spout each add material and an inline process step.
- Finishing. Soft-touch and metallic effects carry a premium over standard gloss or matte.
Where the format can pay for itself: if the replaced solution was a rigid container plus an outer display carton, the flat bottom pouch may remove both. That comparison — total delivered cost of the pack and its carton versus the pouch alone — is the honest way to evaluate the price premium. Comparing pouch-to-pouch unit cost in isolation will always make the flat bottom format look expensive.
Choosing a Supplier: Eight Questions Worth Asking
These questions separate a converter that can execute a flat bottom project from one that merely lists the format.
- Can you supply tested OTR and WVTR data for the structure you are proposing? A barrier claim without measured data is a marketing statement.
- What are your certifications, and what do they actually cover? Ask whether the certification is site-level (covering the factory and process) and whether it applies to food-contact production specifically. Common ones in this industry include BRC, ISO 9001, FSSC 22000, and food-contact compliance with FDA or EU requirements. If you sell into the EU, PPWR compliance requirements also apply to the pack itself. Ask for copies and check the scope and expiry.
- Which print method will you use, and what is the minimum order per design for each? Get the number for both gravure and digital. They are very different.
- Do you provide free dielines and a physical proof before production? A digital proof does not reveal how the artwork wraps across a gusset edge or a base panel. Ask for a printed sample.
- What is your sample process and turnaround? Free printed samples are common in this industry, with the buyer covering freight; a sample lead time of about a week is typical. Confirm both.
- What are your production lead time and its triggers? Lead time usually starts after deposit and artwork approval, and it lengthens with colour count and add-ons. Get the number per scenario you are actually ordering.
- Who owns the printing cylinders? For gravure, understand whether the cylinder cost is a one-off and whether the cylinders are retained for your reorders. This materially affects your second-order economics.
- Can you support a factory audit or provide a virtual tour? For a first order with a new overseas supplier, visual verification of the production environment is a reasonable request.
What Information Do You Need for a Quotation?
Suppliers can only quote accurately when these are known. Sending them together usually removes at least one full round of back-and-forth.
- Product — what exactly is being packed, and is it a food, a cosmetic, or a chemical?
- Fill weight and fill volume — weight alone is not enough; include the product's bulk density or send a physical sample.
- Bag type — confirm "flat bottom / eight-side seal" explicitly, and note whether the shape is fixed or open to recommendation.
- Size — or your target shelf and carton constraints if you want a recommendation.
- Film structure — or target shelf life and storage conditions, if you would rather the supplier propose one.
- Quantity — first order and expected annual reorder volume, since these are often priced differently.
- Printing — number of colours, gravure or digital, and whether artwork is ready.
- Finishing — gloss, matte, soft-touch, metallic, spot UV.
- Add-ons — zipper type and position, degassing valve, tin tie, window, tear notch, hang hole, spout.
- Filling machine — make, model, and pouch-holder spec.
- Destination country and port — determines packing standards and freight.
- Required certifications and compliance documentation — food-contact declarations, migration testing, or market-specific regulation.
- Target delivery date — so lead time can be checked against it rather than assumed.
Frequently Asked Questions
Is a flat bottom pouch the same as an eight-side seal bag?
Yes. In the flexible packaging industry, "flat bottom pouch", "eight-side seal bag", "8-side seal pouch", "box pouch", and "block bottom bag" refer to the same construction — a pouch with a separate flat base panel and two side gussets. The variation in naming reflects different regional and supplier conventions rather than different products. Chinese-speaking suppliers most often use "八边封袋". Always confirm the die line rather than relying on the name when comparing quotes.
How many seals does an eight-side seal bag actually have?
Descriptions in the industry commonly cite eight seal lines, but the exact count depends on the converter's construction and the bag's specific design. Rather than counting seals, verify the functional requirements: that the base is a flat panel, that both side gussets are sealed to the base, and that the finished pouch stands square when filled to your target weight.
Are flat bottom pouches more expensive than stand-up pouches?
Usually yes, on a per-unit basis. The format uses more film and requires more converting steps. The relevant question is total delivered cost: if the flat bottom pouch lets you remove an outer display carton or achieve a higher retail price point, the effective comparison may reverse. Evaluate it against the pack plus carton it replaces, not against a pouch alone.
Can flat bottom pouches hold liquid?
They are not recommended for liquids, sauces, or pastes. The gusset corners and multiple seal intersections concentrate stress under hydrostatic load, and flex-cracking can create pinholes during transport. Spouted pouches, retort pouches, and bottles are more reliable formats for liquid products.
What fill weight suits a flat bottom pouch best?
The structural advantage becomes commercially meaningful at roughly 250 g and above, where base stability visibly affects retail display. Below about 100 g the advantage largely disappears while the cost premium remains, and a stand-up pouch or sachet is usually the better value.
Do flat bottom pouches work with a one-way degassing valve?
Yes, and this is one of the most common combinations for roasted coffee. The valve lets carbon dioxide escape while restricting oxygen ingress. Confirm the valve position sits above the fill line after sealing, and confirm your filling machine can handle valve-equipped premade pouches.
Can they run on a vertical form-fill-seal machine?
Generally not. Flat bottom pouches are designed to be supplied as finished pouches and run on horizontal form-fill-seal or dedicated premade-pouch lines. Complex flat base geometry is difficult to form inline on VFFS equipment. If your line is VFFS-only, raise this at the start of the project rather than after artwork approval.
What is the typical minimum order quantity?
MOQ depends on print method and bag size, not on a single factory-wide number. Gravure printing carries high setup cost per colour and suits larger runs; digital printing supports substantially smaller and multi-design runs at a higher unit cost. Ask for the MOQ for both methods across the sizes you are considering.
How long does production take?
Lead time typically runs from deposit and artwork approval, and extends with colour count, add-ons, and finishing. Sample lead time is usually shorter — often around a week for printed samples. Ask for lead time per configuration rather than a single figure, and check it against your target delivery date.
What barrier structure should I choose for coffee?
Coffee's main degradation risks are oxygen and aroma loss, so foil-containing or high-barrier metallised structures are commonly specified, frequently with a degassing valve. For nuts and dried fruit the priority shifts toward moisture. The right approach is to state your target shelf life and storage conditions, then ask the supplier for tested OTR and WVTR figures for the structure they propose — and to test a filled sample before committing to volume production.
Conclusion
A flat bottom pouch is a presentation-and-capacity decision, not a barrier decision. Choose the format when shelf presence, stability above roughly 250 g, and five printable panels matter to how your product sells. Choose a different format when you are packing liquids, working below about 100 g, selling purely online, or operating on margins that cannot absorb a higher unit cost.
The three specifications that most often cause problems are fill weight against pouch volume, machine compatibility, and whether the claimed barrier performance is backed by measured data. Settling those three questions before artwork approval prevents nearly all of the expensive mistakes in this format.
Browse our flat bottom pouch range, or request a quote with your fill weight, target shelf life, and filling machine details — we will come back with a proposed structure and a physical sample.