Project notes
Understand this estimate
A pour-on mold estimate subtracts the master’s displaced volume from the mold box’s inside volume, then uses the chosen rubber’s mixed density to estimate mass.
How to use the calculator
Measure the inside mold box
Use internal dimensions and the intended fill height, not outside box dimensions.
Inputs Mold-box inside length · Mold-box inside width · Mold-box inside height
Measure master displacement
Enter a displaced volume in US fluid ounces. Do not substitute the master’s bounding-box dimensions.
Inputs Master displacement
Use the current mixed-material density
Enter density from the selected product data. An optional allowance affects material mass and volume, not mold design.
Inputs Mixed material density · Extra allowance
Formula and variables
Box volume = inside length × width × height. Rubber volume = box volume − master displacement (1 US fl oz = 1.8046875 in³). Mixed material mass = volume with allowance × 16.387064 × entered density.
- L × W × HMold-box cavity
- Inside box dimensions.in³
- VₘMaster displacement
- Converted at 1.8046875 in³ per US fluid ounce.US fl oz
- ρMixed density
- Product-specific density input.g/mL
What the result means
Result interpretation
Net rubber volume excludes the master. Volume with allowance and mixed-material mass include the entered allowance. These outputs estimate purchase quantity and do not size a support shell or certify a mold.
Limits and assumptions
Use the actual internal box volume and master displacement. This estimates purchase quantity only; it does not establish mold wall/support design or a universal density.
Worked example
A 10 × 10 × 1 inch box with a measured master
Assumptions
- The box dimensions are internal.
- The selected mixed rubber density is 1.1 g/mL.
- No allowance is added.
Calculation
- Box volume = 10 × 10 × 1 = 100 in³.
- Displacement = 32 × 1.8046875 = 57.75 in³; net = 42.25 in³.
- 42.25 × 16.387064 × 1.1 = 761.6 g = 26.86 oz.
| Net rubber volume | 42.25 in³ |
|---|---|
| Volume with allowance | 42.25 in³ |
| Estimated mixed material | 26.86 US oz |
| Estimated mixed material metric equivalent | 761.6 g |
Common questions
- Can I use the master’s length × width × height as displacement?
- Only if that box truly represents the volume it displaces. For irregular masters, measure displacement directly.
- Does this calculate a safe mold-wall thickness?
- No. Mold geometry, support and handling are not evaluated.