Blown film calculators

Calculations for film, rolls, bubbles, and line output.

Enter your measurements. Results update instantly and are built for practical blown-film work.

Presumes density of 0.9245 g/cm³

Calculate gauge

Gauge (mil) = sample weight ÷ (layflat width × sample length × 0.0303)

Film construction Folded / tubular (two sheets) Single sheet

Sample weight gramsSample width inchesSample length inches

Calculated result

—mil

Folded film counts both layers in the sample weight.

Presumes density of 0.9245 g/cm³

Calculate gram weight

Gram weight = width × sample length × gauge × 0.0303

Film construction Folded / tubular (two sheets) SWS (single sheet)

Sample width inchesSample length inchesTarget gauge mil

Calculated result

—grams

Folded film includes both layers in the target sample weight.

Real-time extrusion rate

Calculate gross line output

lb/hr = nip speed × gram weight × 1.5858 × rolls ÷ sample length

Nip speed ft/minSample weight gramsSample length inchesRolls running count

Calculated result

—lb/hr

Gross output across all rolls running.

Finished-roll estimate

Calculate roll length

Roll length (ft) = (sample length ÷ 12) × 454 × (roll weight - core weight) ÷ sample weight

Roll weight poundsSample weight gramsSample length inches

Calculated result

—feet

Estimated film length on the roll.

Bubble geometry

Calculate blow-up ratio

BUR = bubble diameter ÷ die diameter

Layflat width inchesDie diameter inches

Calculated result

—: 1 BUR

Machine-direction stretch

Calculate draw-down ratio

DDR = die gap ÷ (gauge × BUR)

Die gap milGauge milBlow-up ratio ratio

Calculated result

—: 1 DDR

Die gap and film gauge must use the same thickness units.

Gusseted layflat breakdown

Gusseted width simplified

Total unfolded = first number + second number | Window = first number − second number

Example notation: 48 × 36

Gusseted width first numberCombined gusset sides second number

Total unfolded width—inches

Center window—inches

Each gusset—inches, if equal

ASTM D1709 staircase helper

Dart impact 50% failure weight

P50 = lowest failed weight + increment × ((A ÷ N) − 0.5)

Starting dart mass grams Weight increment grams

A minimum of twenty drops with ten passes and ten failures is required. Calculator will continue until those requirements are met.

Ready

Enter a starting mass and fixed increment, then record each impact. An increment of 15 grams or 30 grams is recommended