PATH-PACK

Free engineering tool · No signup

Pillow Bag Size Calculator

Enter your product dimensions — or just the fill weight — and get the film width and bag length your flow wrapper needs, plus every machine that can run it as standard — from the small-pocket PP180R to the JC wrappers and four-side-seal lines. Buying premade pouches? Switch Bag type to Premade pouch and match the PP series directly.

Dimensions in

Back seal: one film wrapped into a tube, sealed along the back and both ends — the default flow-wrap bag. Four-side seal: flat film sealed on all four edges, typical for flatter products. Premade pouch: you buy the pouch made-to-size and a PP machine fills and seals it — enter the pouch width and height you purchase.

mm
mm
mm

Defaults show a typical 250 g biscuit stack — 120 × 75 × 34 mm.

Advanced — sealing allowances & pack shape

Bag sizes are padded by this margin and rounded up — a slightly large bag is tuned out on the machine, a too-tight one is a rework. Default 5%.

Leave blank unless you buy film at a set width (film stock, an existing line) — the list then keeps only machines whose film web covers it. Sachet lines: this is the frame width the web runs on (JC400 400 · JC600 600 · JC700 700 · JC800/JC800Z 880 mm).

Defaults: fin 25 mm (back seal) · side 18 mm (four-side) · end 30 mm · W:H 3:1 · L:W 1.4:1 · margin 5%. Ratios only apply in weight mode.

Don't trust the table? Measure yours in 5 minutes

  1. Take a 1 L measuring cylinder (or any rigid straight-sided container of known volume).
  2. Fill gently with product — no tapping, no shaking — until level.
  3. Weigh what you poured in. Density (g/cm³) = grams ÷ mL.
  4. Tap the container 50 times, top up, reweigh — that's the settled density for transport checks.

Or send us a 500 g sample and we'll measure it for you, free.

Your bag spec appears here — enter numbers on the left.

Bulk Density Reference Table

Literature-compiled ranges for 57 common packaged materials. Real density moves with moisture, grade and process — treat these as planning numbers and measure yours before cutting tooling. ● classic flow-wrap product · ○ flow-wrappable with tray · — usually a vertical-machine product.

Material Category Loose bulk density Tapped Packed by Flow-wrap fit

All values in g/cm³ (1 g/cm³ = 1 kg/L). Tapped = after settling/vibration, for transport checks. Pending engineering verification — send a sample for a measured value.

How the math works

No black box — this is the same arithmetic a packaging engineer does on a whiteboard.

Mode A — you know the product dimensions

film width = product width + 2 × product height + fin allowance   (default +25 mm)
bag length = product length + end allowance                      (default +30 mm)
tight wrap: bag length = product length + product height + 20 mm

The film wraps the product into a tube — one width, two heights, plus the crimps that form the fin seal. That's why product height hits the film width twice.

Mode B — you only know the fill weight

volume  V = weight ÷ bulk density          (density is a range → so is V)
powders: V × 1.10                          (fresh fill settles in transport)
pack shape: width : height ≈ 3 : 1, length : width ≈ 1.4 : 1
solve W from V, then apply the Mode A formulas

You get a range, not a point — that's physics, not hedging. Size the bag for the light end of your density range.

Four-side-seal pillow bags

bag width  = product width  + 2 × side allowance   (15–20 mm per side)
bag length = product length + 2 × end allowance    (25–30 mm per end)

Four-side sealing runs flat film and seals all four edges, so product height doesn't enter the width formula — it suits relatively flat products. Switch Bag type in the calculator and both formulas swap; weight mode solves the pack first, then applies the same two lines.

Premade-pouch machines (PP series)

Premade pouches are bought to size, not cut from film — so there are no sealing allowances and no fit margin. Enter the pouch width and height exactly as you purchase them, and the calculator matches the PP series directly on those two dimensions (50–440 mm wide, 100–650 mm tall). Zippers, spouts and side gussets narrow the pick further; large side-gusset bags run on the PP880.

The fit margin

Every result is padded by 5% (adjustable under Advanced) and rounded up to whole mm. A bag that's a touch large is tuned out on the machine; a bag calculated tight that the machine can't hold is a rework. Machine matching runs on the padded numbers for the same reason — the machine must hold the realistic bag, not the theoretical one.

Machine matching

A flow wrapper is gated by bag width range, bag length range and product height (the height limit is already inside the film-width formula). Back-seal pillows match the flow family — the roll-fed PP180R (60–90 mm) up through the JC250/JC420 wrappers; four-side-seal bags match the JC sachet lines; premade pouches match the PP series. The calculator checks your result against every model and shows all matches, entry tier first — we don't hide the affordable machines. A model only qualifies when its ranges cover your full calculated range — partly overlapping isn't enough for standard tooling. If nothing covers it, the closest model and custom tooling are quotable engineering work. Already running a set film width? The optional Film roll width field (under Advanced) keeps only machines whose film web covers it — on sachet lines that's the frame width (JC400 400 · JC600 600 · JC700 700 · JC800/JC800Z 880 mm).

What this tool does not do

  • It won't pretend a powder belongs on a horizontal wrapper — loose granular and powder products usually run on vertical (VFFS) machines with a multi-head weigher. It tells you which case you're in.
  • It won't hand you one magic number from a literature density. Ranges, sample measurement, honesty.
  • Film structure, thickness and print layout affect the roll spec — that's a separate conversation (and a separate calculator on our sister site).

FAQ

How do I calculate a pillow bag size from product weight?

Divide fill weight by bulk density to get volume, assume a pack cross-section of about 3:1, solve the pack dims, then apply the flow-wrap formula. The calculator does the whole chain — with the density range, because real bulk density varies.

Is film width the same as bag width on a flow wrapper?

Yes — the "bag width" on a spec sheet is the film web width: product width + two product heights + fin allowance. Bag length runs along the machine direction.

Back-seal or four-side-seal — which pillow bag do I need?

Back-seal (one film wrapped into a tube, sealed on the back and both ends) is the standard flow-wrap bag — the calculator's default. Four-side-seal runs flat film sealed on all four edges and suits flatter products: add 15–20 mm per side on width and 25–30 mm per end on length. Switch Bag type and the formulas swap. Every JC model runs both bag types.

Flat pouch or four-side-seal — which bag type is mine?

They look identical — flat, sealed on all four edges — but the process differs. Four-side-seal: the machine forms the bag from roll film and seals all four edges in one pass (Path Pack JC series). Premade flat pouch: you buy the bag ready-made and a PP machine opens, fills and seals it. Rule of thumb: film from a roll → Four-side-seal; bags you purchase → Premade pouch. The calculator treats them differently too — four-side-seal sizes the bag from your product plus sealing allowances, premade pouch matches the purchased width × height exactly.

Why does the result show a range instead of one number?

Bulk density is a range, not a constant. We size for the lightest case and show the bracket. For an exact number, send a 500 g sample — we measure free.

I fill premade pouches, not roll film — which machine?

Switch Bag type to Premade pouch and enter the pouch width and height you buy. No allowances or fit margin apply — the pouch is purchased to spec, not cut from film — so matching runs straight on those dimensions against the PP series: 50–440 mm pouch width, 100–650 mm pouch height, 15–160 pouches/min. Bring the pouch spec (zipper, spout, side gusset) and the pick narrows further.

My product is very light and bulky — potato chips, popcorn?

Low-density products (0.05–0.12 g/cm³) need large bags with headspace and usually nitrogen flushing. On a horizontal wrapper they run in a tray; loose fill usually goes vertical. The calculator flags which case you're in.

Which Path Pack machine fits my bag?

Matching is mechanical: your film width and bag length against each model's ranges. Back-seal pillows match the flow family — the roll-fed PP180R (60–90 mm film width), JC250 and JC420; four-side-seal bags match the JC sachet lines from the JC400 (85–160 mm) to the JC800Z (up to 220 × 280 mm). Every fitting model is shown, entry tier first.

My bag is only a few millimetres outside a machine's range — what now?

The calculator pads your cut size by a fit margin (5% default) before matching — the machine must hold the realistic bag, not the theoretical one. If the padded size misses an envelope by just a few millimetres, the result card says exactly how many. Tightening the side/end allowance to the spec minimums (15 / 25 mm) or lowering the fit margin may bring it back inside; if the bag is too small for every model, small-format tooling is quotable engineering work either way — send the drawing.

How accurate are the density values?

Literature-compiled ranges, pending engineering verification, and they move with moisture and grade. Planning numbers, not tooling numbers. Measure yours (5-minute guide above) or send a sample.