Direct Answer: A flat bottom pouch (also called an eight-side seal, box, or block-bottom pouch) typically holds about 100 g in a 120 × 70 × 200 mm bag and up to roughly 5 kg in a 280 × 160 × 550 mm bag. The number on the front of the pack is not set by the dimensions alone — it is set by product density, required headspace, and filling method. Use the reference chart below as a starting point, then confirm the real fill weight with samples filled on your own line.
Flat bottom, eight-side seal, box, block bottom — the same structure
In flexible packaging, a flat bottom pouch, eight-side seal bag, 8-side seal pouch, box pouch, and block bottom bag are different industry names for the exact same structure: a pouch with a sealed rectangular base that lets it stand on its own, plus two side gussets that lay flat to form that base. Chinese converters often list it as 八边封袋 ("eight-side seal bag"), while English-speaking buyers usually search for "flat bottom pouch." If you are comparing quotes, treat these terms as interchangeable and compare the actual dimensions and material structure, not the label.
Flat bottom pouch size & fill-weight reference (100 g – 5 kg)
The table below collects common industry reference sizes (Width × Depth × Height in millimetres). These are published starting points from several converters, not Sinoflex specifications, and every source agrees on the same caveat: actual capacity varies with product density, shape, settling, and headspace. Always verify against a filled sample.
| Net weight (reference) | W × D × H (mm) | Typical use |
|---|---|---|
| ~50 g | 100 × 60 × 150 | Tea samples, spice sachets |
| ~100 g | 120 × 70 × 200 | Premium tea, small coffee |
| ~250 g | 130 × 80 × 265 | Standard coffee, snacks |
| ~500 g | 150 × 95 × 320 | Family coffee, pet treats |
| ~1 kg | 180 × 110 × 380 | Bulk coffee, pet food |
| ~2 kg | 220 × 130 × 450 | Large pet food, bulk nuts |
| ~5 kg | 280 × 160 × 550 | Commercial / wholesale |
Why a range, not a fixed number: one published reference lists a 150 × 95 × 320 mm flat bottom bag at about 415 g for coffee, but only about 300 g for pet food and 184 g for loose tea — same volume, different mass, because bulk density differs. Read the chart as geometry to start from, never as a guaranteed fill weight.
Why the same bag holds different weights
Capacity is a volume; the net weight printed on the pack is mass. The two are linked only by bulk density (how many grams occupy one litre when filled the way your product actually packs):
- Density: Coffee beans, pet kibble, protein powder, and granola all fill the same pouch to very different weights. Denser products simply weigh more per litre.
- Headspace: You need clearance above the product for the top seal, for a zipper if present, and for slack so the seams are not strained. Most references allow 15–20% above the calculated product volume.
- Settling: Granular products can settle 10–15% in transit. A pouch that looks full at the filling line can look half-empty on the shelf if you do not plan for it.
- Filling method: Auger, volumetric cup, and weigher filling each pack the product slightly differently, which shifts the real fill weight for a given size.
What the three dimensions mean (and why the gusset is the bottom)
A flat bottom pouch is measured as Width (W) × Depth (D) × Height (H):
- Width (W): The front-face measurement, left to right. It drives shelf presence and printable label area.
- Depth (D): The side-gusset measurement, front to back. On a flat bottom / box pouch, the gusset depth is the standing bottom width — it is what lets the bag stand square.
- Height (H): Top to bottom, including the top seal area. It sets total volume.
A practical rule of thumb used by converters: bag width ≈ product width + 20 mm, bag height ≈ product height + 50 mm (for the seal area), and bag depth ≈ 50–60% of width for stable standing. Treat it as a starting estimate, not a formula.
How to choose the right size: a 6-step method
- Define the target fill weight. Start from the number that goes on the front of the pack (100 g, 250 g, 500 g, 1 kg are common retail weights for a reason — shoppers compare across a shelf).
- Measure bulk density. Fill a container of known volume the way your product will actually be filled, weigh it, repeat two or three times, and average. You now know grams per litre.
- Estimate required volume. Required volume ≈ product weight ÷ bulk density.
- Allow headspace. Add roughly 10–15% above the calculated volume for the seal, zipper, and settling.
- Pick the nearest size. Match the total to the chart; if you are between two sizes, size up. An underfilled pouch reads as poor value; a slightly generous one just looks well packed.
- Test with the actual product. Order samples in the chosen size, fill them on your real equipment, and check three things: does it stand straight when full, does the seal close cleanly, and does it still look right after shipping?
Fill weight by product type: coffee, pet food, tea, snacks
Because bulk density differs by product, the same flat bottom size lands at different net weights. As a concrete illustration, one supplier's published reference for a 150 × 95 × 320 mm bag shows coffee near the top of the range and tea near the bottom. When you brief a converter, state the product type and density, not just the target grammage — that is what lets them recommend the accurate size. For deeper background by application, see our guides on coffee packaging, pet food packaging, tea packaging, and snack packaging.
Common sizing mistakes to avoid
- Guessing by weight alone. "8 oz" means different dimensions depending on density, shape, and headspace. Start from volume.
- Underfilling. A pouch filled below roughly 80–85% looks like poor value on the shelf. Aim for 80–85% fill for the best presentation.
- Ignoring density. Specifying a size from a coffee example, then filling pet kibble or powder, will miss the real weight.
- Skipping the sample test. Charts and formulas get you to a shortlist, not a decision. Test the actual product on the actual line before a production run.
Flat bottom vs stand-up: does size choice differ?
The two formats handle volume differently. For the same footprint, a flat bottom pouch generally gives more structure and more usable capacity because its box base uses the full depth, while a standard stand-up pouch's rounded base wastes some of that space. Both are custom-converted, so neither has a fixed size ladder — but if shelf presence and a squared premium look matter, the flat bottom format is usually the one to test first for products above roughly 250 g. The full comparison, with a side-by-side table, is in our flat bottom pouch buyer's guide.
What to send your supplier for a quote
To get an accurate size recommendation and price, send your converter:
- The product and its net weight;
- Its bulk density (or a sample to measure it);
- Your target size or dimensions, or the fill weight if you want them to propose a size;
- The material / barrier structure (for freshness-sensitive products, a foil or metallised layer is common — see aluminium foil pouches);
- Closure needs (zipper, one-way degassing valve for coffee — see our coffee valve guide);
- Print requirements (colours, finish);
- Order quantity and your filling method.
Request samples in your chosen size and fill them on your line before committing to a production run. To start a conversation with our team, visit the contact page or the flat bottom pouch product page.
Frequently asked questions
What size flat bottom pouch do I need for 250 g of coffee?
A common reference size is about 130 × 80 × 265 mm (W × D × H), which is the most popular 250 g coffee size across published converter charts. Confirm the real fill with a sample, because the same bag holds less if your coffee is ground finer or packed differently.
How much does a 1 kg flat bottom pouch hold?
A common reference size is about 180 × 110 × 380 mm, listed by converters as a ~1 kg format for bulk coffee and pet food. The actual weight depends on product density — a 1 kg reference bag may hold noticeably less of a light, airy product.
Does gusset depth equal the bottom width on a flat bottom pouch?
Yes. On a flat bottom, box, or eight-side seal pouch, the side-gusset depth is the standing bottom width. The bag is measured Width × Depth × Height, where Depth is that gusset and is what makes the pouch stand square on the shelf.
Why does the same pouch hold different weights for different products?
Capacity is a volume; net weight is mass, and the two meet only at bulk density. Coffee beans, pet kibble, protein powder, and tea all pack to different grams per litre, so the same dimensions yield different fill weights. Headspace, settling, and filling method add further variation.
How full should a flat bottom pouch be when packed?
Aim for roughly 80–85% full. Underfilling makes the pack look like poor value on the shelf; a slightly generous fill just looks well packed. Leave 10–20% above the product for the top seal, any zipper, and settling in transit.
Can flat bottom pouches be made larger than 1 kg?
Yes. Flat bottom pouches are fully custom and are regularly made well above 1 kg; a common reference size for about 5 kg is roughly 280 × 160 × 550 mm. Capacity scales with the dimensions, so larger formats are a matter of specifying Width, Depth, and Height for your product and filling line.
Flat bottom pouch vs stand-up pouch: which holds more for the same footprint?
For the same footprint, a flat bottom pouch generally offers more structure and more usable capacity because its box base uses the full depth, while a stand-up pouch's rounded base wastes some space. Both are custom-converted, so neither has fixed sizes — pick by shelf presence, capacity, and filling method.
How do I size a pouch for an unusual or very dense product?
Measure bulk density (grams per litre) by filling a known volume the way you will actually pack, then compute required volume as weight ÷ density, add 10–20% headspace, and pick the nearest reference size. Always confirm with a sample filled on your real equipment.
What information should I send to get a flat bottom pouch quoted?
Send the product and net weight, bulk density (or a sample), target size or dimensions, material and barrier structure, closure needs (zipper or valve), print requirements, order quantity, and your filling method. Samples in the chosen size, filled on your line, should come before a production run.