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Thermoforming Draw Ratio Calculator

Calculate areal and linear draw ratios for thermoformed parts. Estimates wall thinning, minimum wall thickness, and forming feasibility.

Inputs

Results

Areal draw ratio

2.62

Min wall thickness (mm)

0.57

Linear draw ratio (H:W)0.5
Avg wall thickness (mm)0.93
Max thinning (%)61.9
Formed surface area (mm²)78,701.6
Opening area (mm²)30,000
Feasibility (1-4)2
Sheet length needed (mm)250
Sheet width needed (mm)200
How to Use This Calculator
  1. Enter Shape (1=box, 2=cup), Cavity length (mm), and Cavity width / diameter (mm).
  2. Set Draw depth (mm), Sheet thickness (mm), and Draft angle (°).
  3. Review Areal draw ratio and Min wall thickness (mm).
  4. Use Linear draw ratio (H:W) and Avg wall thickness (mm) to inform your decision.

How the result changes with Draw depth (mm)

Draw depth (mm)Areal draw ratioMin wall thickness (mm)
2005.160.29
70013.250.11
1,30018.580.08
1,80021.770.07

What each input means

Shape (1=box, 2=cup)
1 = rectangular box, 2 = cylindrical cup.
Cavity length (mm)
Length of the cavity opening.
Cavity width / diameter (mm)
Width (box) or diameter (cup) of the cavity opening.
Draw depth (mm)
Depth the sheet is drawn into the cavity.
Sheet thickness (mm)
Original plastic sheet gauge thickness.
Draft angle (°)
Mold draft angle for part release. Typical: 2-5°.

What each result means

Areal draw ratio
Ratio of formed surface area to opening area. <3 is typical.
Linear draw ratio (H:W)
Depth divided by the smaller opening dimension.
Min wall thickness (mm)
Estimated thinnest wall section (at corners/bottom edges).
Avg wall thickness (mm)
Estimated average wall thickness of the formed part.
Max thinning (%)
Maximum wall thinning as percentage of original sheet.
Formed surface area (mm²)
Total surface area of the formed part.
Opening area (mm²)
Area of the mold cavity opening.
Feasibility (1-4)
1 = easy, 2 = moderate, 3 = difficult, 4 = likely not feasible.
Sheet length needed (mm)
Minimum sheet length including 25mm trim allowance per side.
Sheet width needed (mm)
Minimum sheet width including trim allowance.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Shape (1=box, 2=cup) = 1, Cavity length (mm) = 200, Cavity width / diameter (mm) = 150, Draw depth (mm) = 75 = 6 input(s) provided
  2. Calculate Areal draw ratio
    2.623 = 2.623
  3. Calculate Min wall thickness
    Min wall thickness = sheetThickness / arealDrawRatio
    0.572 = 0.572
  4. Calculate Linear draw ratio
    Linear draw ratio
    0.5 = 0.5
  5. Calculate Avg wall thickness
    Avg wall thickness = sheetThickness / sqrt(arealDrawRatio)
    0.926 = 0.926

Engine last updated .

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