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Epoxy Resin Calculator
Work out exactly how much epoxy resin to mix for a pour, coating or casting. Pick a shape, enter dimensions, and get total volume, approximate weight and how much Part A and Part B to measure.
Formula
Rectangle: V (in³) = length × width × depth
Circle: V (in³) = π × (diameter ÷ 2)² × depth
With waste: V_total = V × (1 + waste% ÷ 100)
Gallons = V_total ÷ 231 Fluid ounces = V_total ÷ 1.8047
Liters = V_total × 0.016387 Weight (g) = ml × density
1:1 → A = B = total ÷ 2 2:1 → A = total × 2/3, B = total × 1/3How to use the epoxy calculator
- Choose the shape that matches your project. Use Custom volume if you already know the volume (for example from a mold).
- Select units and enter dimensions. Convert depth carefully: 1/8 inch = 0.125 in, 1/4 inch = 0.25 in.
- Add a waste allowance. Some resin always stays in the cup, on the stir stick and on the edges; 10–15% is a common buffer for small projects.
- Read the volume and the A/B split for your product's mix ratio.
Worked example
A 24 × 12 inch serving board coated 1/8 inch thick: 24 × 12 × 0.125 = 36 in³. Dividing by 1.8047 gives about 19.9 fl oz (0.156 gal). With 10% extra that becomes about 21.9 fl oz — roughly 11 oz of Part A and 11 oz of Part B for a 1:1 epoxy, or about 14.6 oz A and 7.3 oz B for a 2:1 epoxy.
Volume ratio vs weight ratio
The A/B amounts above are by volume. Some manufacturers specify the ratio by weight instead, and because resin and hardener usually have different densities, a 2:1 by volume mix is not the same as 2:1 by weight. Always use the measuring method printed on your kit.
Unit conversions used
- 1 US gallon = 231 in³ = 128 US fl oz
- 1 US fl oz = 1.8047 in³ = 29.5735 ml
- 1 in³ = 16.387 ml; 1 ft³ = 1,728 in³ ≈ 7.48 gal
- Weight = volume (cm³) × density. Many mixed epoxies are roughly 1.05–1.2 g/cm³; the default 1.1 is an approximation — check your product's technical data sheet and edit the field.
Frequently asked questions
How much epoxy do I need for a 1/8 inch coat?
Multiply length × width in inches by 0.125 to get cubic inches, then divide by 231 for gallons or by 1.8047 for fluid ounces. One square foot at 1/8 inch is 18 in³, about 10 fl oz.
How many square feet does a gallon of epoxy cover?
At 1/8 inch thick, one US gallon (231 in³) covers 231 ÷ 18 ≈ 12.8 sq ft. At 1/16 inch it covers about 25.7 sq ft. Real coverage is lower because of runoff and waste.
Is the 1:1 or 2:1 result by weight or by volume?
By volume. If your product lists a ratio by weight, measure with a scale and follow the manufacturer's numbers.
How much extra epoxy should I mix?
A 10–15% allowance covers resin left in cups and drips for most small projects. Flood coats that run off the edges may need more.
What density should I use for epoxy?
Mixed epoxy is commonly around 1.1 g/cm³, but it varies by product. Find the specific gravity on the technical data sheet and enter it for a better weight estimate.