Gusseted Box Liner Size Calculator
Enter a box’s inside dimensions to get a side-gusseted liner size written for ordering. The calculator also estimates two-wall film area and resin weight for one liner and the full quantity.
Size to order26.00 × 16.00 × 46.00 in
- Closed face width (in)
- 26
- Total gusset depth (in)
- 16
- Folded side gusset, each (in)
- 8
- Open bag width (in)
- 42
- Cut length (in)
- 46
- Film area per liner (sq ft)
- 26.83
- Estimated weight per liner
- 4.04 oz (114.67 g)
- Estimated batch film weight
- 25.28 lb (11.47 kg)
Ordering dimensions are shown as closed face width × total gusset depth × cut length, rounded upward to 0.01 of the selected unit.
Film weight is based on two film walls only and excludes seal tails, trim, printing, additives, and manufacturing variation.
How to use this calculator
- Measure the container’s inside length, width, and height rather than its outside dimensions.
- Choose inches or millimetres and enter all three dimensions in that unit.
- Add enough loose-fit and top-closure allowance for loading and the way the liner will be closed.
- Enter the nominal film thickness, density, and planned quantity to estimate material use.
- Use the order size as a starting specification, then confirm stock sizes and tolerances with the bag converter.
How to size a gusseted box liner
A side-gusseted liner is normally ordered as closed face width × total gusset depth × cut length. The gusset is the total depth across both folded sides, not the depth of one side alone. A supplier may call this notation width × depth × length. The calculator first compares the two base dimensions so that the longer side becomes the face of the bag, even if the measurements were entered in the other order.
Let A be the longer inside base dimension, B the shorter one, H the inside height, C the loose-fit allowance, and T the top-closure allowance. The sizing formulas are:
F = A + C
G = B
O = F + G
N = H + B + T
- F is closed face width.
- G is total gusset depth, so each folded side gusset is
G ÷ 2. - O is open bag width.
- N is cut length.
The length includes the short base dimension because the film has to travel from the rim, around the box bottom, and back up the opposite side. Closure allowance is added above that fitted length for folding, overlap, or a tie. The calculator rounds the displayed order dimensions upward to 0.01 of the selected unit so that display rounding does not make a liner smaller than the calculated size.
Film area and weight
The open bag has two walls. After converting the open width and cut length to centimetres, the film area is S = 2 × O × N. With nominal thickness t in micrometres and density ρ in grams per cubic centimetre, estimated liner mass is M = S × (t ÷ 10,000) × ρ. The batch estimate is simply M × Q, where Q is the number of liners.
Base dimensions, the fit allowance, and the closure allowance move the material use most because they change width or length. Thickness and density scale the weight directly: doubling either one doubles the estimate. Use the actual resin density from the film specification when it is known; 0.92 g/cm³ is a planning value for typical low-density polyethylene.
What this calculator leaves out
This calculation is for a rectangular container and uniform film, not a manufacturing drawing. It does not account for seal tails, trim, printing, additives, uneven gauge, bag-making tolerances, or irregular contents. A stock liner can also need a larger allowance for loading equipment or a different closure method. Confirm the final dimension and construction with the converter, then trial a sample liner before a production order.
Worked example
For a box with a 24 in by 16 in inside base and an 18 in inside height, use a 2 in loose-fit allowance and 12 in top-closure allowance. The order size is (24 + 2) × 16 × (18 + 16 + 12), or 26.00 × 16.00 × 46.00 in. Each folded side gusset is 8 in, and the open bag width is 42 in.
At 50 µm film and 0.92 g/cm³ density, two walls cover 2 × 42 × 46 = 3,864 in², or 26.83 sq ft. That is about 114.67 g (4.04 oz) per liner. For 100 liners, the estimate is 11.47 kg (25.28 lb) of film before production trim and variation.
Common questions
How are side-gusseted liner dimensions written?
Side-gusseted bags are commonly written as width × depth × length. For this calculator, width means the closed face width, depth is the total side-gusset depth, and length is the cut length. Ask the supplier to confirm its notation before ordering because catalogue conventions can differ.
Is gusset depth the total depth or the fold on each side?
This calculator reports total gusset depth: the short inside base dimension of the box. Each of the two folded side gussets is half that measurement. Showing both prevents accidentally specifying twice the required depth to a supplier.
Why does liner length include the box width?
The liner needs enough length to go down one inside wall, across the box bottom, and up the opposite wall. The short base dimension is therefore part of the fitted length. The closure allowance is additional material left above the rim.
How much loose-fit and closure allowance should I add?
One to two inches of loose-fit allowance is a common starting point for a rectangular container, but the needed amount depends on loading and the liner’s stiffness. Choose closure allowance for the planned fold, overlap, or tie-off, then verify it with a physical sample. Close-fitting or irregular contents often need more room.
How do microns compare with mil thickness?
A micron is one thousandth of a millimetre, while a mil is one thousandth of an inch. One mil equals 25.4 µm, so a 50 µm film is about 1.97 mil. Thickness alone does not establish puncture resistance because resin, additives, seal design, and the contents also matter.
Why can actual bag weight differ from the estimate?
The estimate treats both film walls as uniform and uses the entered nominal thickness and density. Real bags include seals, trim, gauge variation, printing, additives, and normal conversion tolerances. Use it for material planning, then obtain the supplier’s actual bag weight for purchasing or freight calculations.