The calculation, without hidden assumptions
Turn measured product dimensions into a transparent starting bag specification. Choose a flat layflat bag or gusseted bag, keep loading and closure allowances explicit, and compare the calculated minimum with stocked sizes before ordering.
How to use this calculator
Measure the packed product at its widest, deepest and longest points.
Choose flat or gusseted bag construction.
Select the measurement unit used by your supplier.
Set loading/width, depth and closure allowances to match the bag supplier and sealing process.
Round the calculated minimum upward to a stocked size, then validate insertion and closure with a physical sample.
Where people use it
- •Size open-ended poly bags around rigid products.
- •Estimate gusseted bags for cartons, bins and bulky items.
- •Compare inch and metric supplier catalogs without mental conversion.
- •Document the exact clearance assumptions behind a purchasing request.
- •Check whether a current bag has enough nominal width and closure length.
10 × 6 × 8 in rigid carton
Using a 1 in loading allowance and 2 in closure allowance, the flat-bag planning rule gives 17 in minimum layflat width and 16 in minimum length. A gusseted model with 1 in width/depth allowance gives 11 × 7 × 16 in before rounding up to a stocked size.
What the result does not assume
- •These are geometric planning rules, not a universal packaging standard; supplier measuring conventions can differ.
- •Measure the product after any bubble wrap, padding or bundling that will go inside the bag.
- •Reclosable zipper/header/lip dimensions can reduce usable length; confirm how the supplier states usable dimensions.
- •Film mil or micron thickness is a separate material specification and does not by itself certify puncture strength, load capacity, food contact, antistatic or VCI performance.
- •Soft, compressible, sharp or irregular products need physical fit testing rather than geometry alone.
- •Always round up to an available size; never round a calculated minimum downward.
Frequently asked questions
How do I calculate flat poly bag size?+
A common rigid-item planning rule is layflat width = product width + product depth + loading allowance, and bag length = product length + product depth + closure allowance. Keep the allowances explicit because suppliers and sealing processes differ.
How are poly bags measured?+
Flat bags are commonly stated as width × length. Gusseted bags add a depth/gusset dimension, but supplier conventions should be checked before ordering.
Why does product depth affect a flat bag?+
A flat tube must open around the product thickness, so depth consumes part of the available layflat width and length.
Should I round the result up?+
Yes. Treat the result as a minimum geometry and round upward to a stocked size, then test insertion and closure.
Does this calculator choose film thickness?+
No. Gauge selection depends on product edges, weight, handling, material and compliance needs; the calculator intentionally keeps size separate from performance claims.
Can I use this for zipper bags?+
Use it as a starting geometry only. Confirm whether the supplier measures usable length below the zipper and add any required header or closure allowance.
Semantic next steps
Continue the calculation
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Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.