Thermoforming Sheet Thickness Calculator — Free Tool to Choose the Right Plastic Sheet
Input mold depth, draw ratio and product diameter to quickly get engineering-grade recommended sheet thickness (mm), tolerance range and material suggestions. No registration required, free to download results.
Try CalculatorThermoforming Sheet Thickness Calculator
Enter your parameters below to get instant recommendations
Linear draw ratio = Blank diameter / Formed diameter (common). If you have area draw ratio, please select area definition in advanced settings.
Results
Enter your parameters and click "Calculate" to see the recommended sheet thickness based on your inputs.
Material Suggestion
Select a material in the advanced settings to get specific recommendations.
How It Works
Understand the calculation methods behind our recommendations
Empirical Method Based on Industry Experience
This method uses practical industry experience to provide conservative recommendations that account for real-world forming conditions and material behavior.
Key Formula:
Recommended Thickness = Target Final Thickness × Draw-Down Factor (Fdd)
Where:
- Draw-Down Factor (Fdd) = 1 + 0.35 × (DR - 1) + 0.02 × (Depth / 50)
- DR = Draw Ratio (linear, ≥1)
- Depth = Mold Depth (mm)
Why this works:
The formula accounts for increased stretching with higher draw ratios and deeper molds. The coefficients (0.35 and 0.02) are derived from industry experience with common thermoforming materials.
Note: These are engineering estimates. Actual forming thickness distribution is affected by mold geometry, vacuum/pressure, forming temperature, and material strain hardening. Use this calculator as a starting point and verify with trial runs.
Theoretical Method Based on Mass Conservation
This method provides a theoretical minimum thickness based on volume/mass conservation principles, ignoring practical forming complexities.
Key Formula:
Initial Thickness ≈ Final Average Thickness / DR2
Where:
- DR = Draw Ratio (linear)
- If area draw ratio is used: Initial Thickness ≈ Final Average Thickness / Area DR
Limitations:
- Assumes uniform thickness distribution (not realistic in actual forming)
- Doesn't account for material thinning in deep draws or corners
- Ignores practical factors like webbing, material memory, and temperature effects
Use case: This method provides a theoretical lower bound for reference, but empirical methods are recommended for actual production.
Industry Examples
See how the calculator works with common thermoforming applications
Lunch Tray (Shallow Form)
Fdd = 1 + 0.35×(0.2) + 0.02×(10/50) = 1.074
Recommended ≈ 0.86 mm → 0.9 mm (rounded up to standard sheet)
Deep Dome Container
Fdd = 1 + 0.35×0.8 + 0.02×(60/50) = 1.304
Recommended = 1.30 mm → 1.4 mm (with margin)
Medical Tray
Fdd = 1 + 0.35×0.5 + 0.02×(25/50) = 1.185
Recommended ≈ 0.71 mm → 0.8 mm (rounded up)
Frequently Asked Questions
Find answers to common questions about thermoforming sheet thickness
The tool uses industry empirical method (Method B) based on draw ratio and mold depth to provide conservative recommendations. You can also input your target average thickness in the "Advanced" section for more precise results.
The results are estimates. Use them as a starting point for material selection and verify with trial runs. For custom molds or production support, please contact our engineers.
By default, we use linear definition (Blank diameter ÷ Formed diameter). If you're using area draw ratio, please switch to "Area draw ratio" in advanced settings.
The default 20% margin works for most applications. For complex geometries or critical applications, increase to 30-50%. For simple forms with well-known materials, you might reduce to 10-15% based on experience.
Different materials have varying stretch characteristics. PET generally allows more stretching than PP or PS. When you select a material, we adjust recommendations based on typical behavior for that material class.
The theoretical minimum assumes perfect material distribution, which never happens in practice. The empirical recommendation accounts for real-world thinning in corners and deep draws that aren't captured by simple volume conservation.
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