PATH-PACK

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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 JC machine that can run it as standard.

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.

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%.

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 53 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.

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). The calculator checks your result against every JC 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. Every JC model runs both bag types — back-seal flow wrap and four-side-seal pillow (the JC400 single-lane, the JC600/JC800Z in multi-lane configurations).

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 — JC400 single-lane, JC600/JC800Z multi-lane.

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.

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 JC model's ranges — from the JC400 Desktop (30–50 mm) to the JC800Z (up to 250 × 350 mm). Every fitting model is shown, entry tier first.

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.