Resin Calculator
Running out of epoxy resin mid-pour, or mixing more than you need and wasting an expensive product, are common frustrations for resin crafters. This resin volume calculator removes the guesswork by computing the exact volume of mixed resin required for your mold, then splitting it into the correct Part A and Part B amounts based on your chosen mix ratio. You select your mold shape (rectangle, cylinder, sphere, or half-sphere), enter dimensions in either centimetres or inches, and choose a 1:1 or 2:1 mix ratio. The calculator converts dimensions to centimetres if needed, computes the geometric volume in millilitres (cubic centimetres), and outputs both ml and fluid ounce volumes for Parts A and B. Note that this gives the theoretical fill volume: always prepare 5 to 10 percent extra to account for mixing losses and surface effects. Check your resin manufacturer's data sheet for the correct mix ratio and maximum pour depth before starting.
Total resin needed: -- ml (-- fl oz). Part A: -- ml, Part B: -- ml.
How the resin calculator works
Dimensions are converted to centimetres if entered in inches (1 inch = 2.54 cm). Volume is computed in cm³ which equals ml. The total volume is then split into Part A and Part B based on the mix ratio.
Rectangle: V = L × W × H (cm³)
Cylinder: V = π × r² × H (cm³)
Sphere: V = (4/3) × π × r³ (cm³)
Half-sphere: V = (2/3) × π × r³ (cm³)
1 inch = 2.54 cm; 1 ml = 0.033814 fl oz
1:1 ratio: Part A = Part B = V / 2
2:1 ratio: Part A = 2V / 3, Part B = V / 3
Worked example
Rectangle mold: 10 cm × 10 cm × 2 cm, 1:1 mix ratio:
- Volume = 10 × 10 × 2 = 200 ml
- In fl oz: 200 × 0.033814 = 6.76 fl oz
- Part A (1:1): 200 / 2 = 100 ml
- Part B (1:1): 200 / 2 = 100 ml
Shape and mix ratio reference
| Shape | Formula | Inputs needed |
|---|---|---|
| Rectangle | L × W × H | Length, Width, Height |
| Cylinder | π × r² × H | Radius, Height |
| Sphere | (4/3) × π × r³ | Radius |
| Half-sphere | (2/3) × π × r³ | Radius |
| Mix ratio | Part A fraction | Part B fraction |
|---|---|---|
| 1:1 | 50% | 50% |
| 2:1 | 66.7% | 33.3% |
Frequently asked questions
How do I calculate resin for a rectangular mold?
For a rectangular or box-shaped mold, multiply the length by the width by the height. All three dimensions must be in the same unit. If you measure in centimetres, the result is in cubic centimetres (cm3), which equals millilitres (ml). If you measure in inches, multiply the result in cubic inches by 16.387 to convert to ml. This calculator handles the unit conversion automatically.
What is the difference between a 1:1 and 2:1 mix ratio?
Epoxy resins are two-part systems: Part A (resin) and Part B (hardener). A 1:1 ratio means you mix equal volumes of Part A and Part B. A 2:1 ratio means you mix two parts of Part A to one part of Part B by volume. Always check your specific resin brand's data sheet, as using the wrong ratio will result in a sticky, uncured pour. This calculator gives you the individual part volumes once you select the ratio.
Why is the calculated volume approximate?
The calculator computes the geometric volume of the mold based on the dimensions you enter. In practice, you may need slightly more resin due to surface tension pulling resin up the mold walls, slight measurement inaccuracies in the mold itself, or resin loss from mixing vessels and tools. A common practice is to prepare 5 to 10 percent more resin than the calculated volume, especially for large or deep pours.
Can I use this calculator for deep pours?
This calculator gives you the total volume needed for a mold of the shape you select. However, many epoxy resins have a maximum depth per pour (often 1 to 2 cm for standard resins, up to 5 cm for deep-pour resins). If your mold is deeper than the manufacturer's maximum pour depth, you will need to pour in layers, allowing each layer to partially cure before adding the next. Always check your resin manufacturer's guidelines for maximum pour depth.
How do I convert the output to grams or ounces by weight?
Epoxy resin density varies by brand, but a common density is approximately 1.1 g/ml for Part A and around 0.95 to 1.05 g/ml for Part B. If your resin instructions specify mixing by weight rather than volume, multiply the volume in ml by the density in g/ml to get grams. This calculator outputs volumes (ml and fl oz), not weights, because mix ratios for most consumer resins are specified by volume.
Official sources
- Standard geometric volume formulas (rectangle, cylinder, sphere) as used in mathematics and engineering.
- Epoxy resin mix ratios per manufacturer data sheets (1:1 and 2:1 by volume are the two standard ratios in the craft resin industry).
- Unit conversion: 1 fluid ounce = 29.5735 ml (US customary); 1 inch = 2.54 cm (international standard).
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.