Epoxy volume formula: how much resin a pour or a coat needs
Epoxy does not shrink or expand enough to matter for an estimate, so the amount to mix is the volume of the space it fills. For a rectangular mould or a flat coat that is length × width × depth. For a round form it is π × radius × radius × depth. For a river between two slabs, use the length of the table, the average width of the gap and the depth of the pour.
Measure everything in the same unit, then convert once at the end. One US gallon is exactly 231 cubic inches and holds 128 US fluid ounces; one litre is 1,000 cubic centimetres. Example: a top 96 in long and 48 in wide, coated 1 in deep, is 96 × 48 × 1 = 4,608 cubic inches, and 4,608 ÷ 231 = 19.95 US gallons.
The same formula read backwards gives coverage: area = volume ÷ thickness. A gallon spread 1/8 in thick covers 231 ÷ 0.125 = 1,848 square inches, which is 12.83 square feet. Halve the thickness and the area doubles. The charts below are that one division, done for common thicknesses.
Then add an allowance for what stays in the cup, on the stir stick and in the pores of the wood. Sellers' calculators commonly suggest 5 to 10 percent. The epoxy resin volume calculator and the epoxy coverage calculator take the allowance as a percentage and show it as its own line, so you can see what the geometry needs and what the allowance adds.
A deep pour is the same volume, split. If the product's data sheet gives a maximum depth for one pour, divide the total depth by that maximum and round up to get the number of layers; equal layers are the total depth divided by that number. The deep pour layer calculator does this and gives the volume to mix for each layer.
Limits: these are geometric estimates. Live edges, knots, voids and wood that soaks up resin all change the real amount, and an average river width is only as good as the measurements behind it. The maximum depth for one pour and the coat thickness come from your product's data sheet, not from this site.
Coverage chart: square feet covered, by coat thickness (inches) and amount of mixed epoxy (US gallons)
One coat, no waste allowance: the area is the volume divided by the thickness. Down the side is the coat thickness, across the top the amount of mixed epoxy, in the units named in the heading.
| Epoxy you have | |||||
|---|---|---|---|---|---|
| Thickness of one coat | 0.5 US gal | 1 US gal | 2 US gal | 3 US gal | 5 US gal |
| 0.0625 in | 12.83 ft² | 25.67 ft² | 51.33 ft² | 77.00 ft² | 128.33 ft² |
| 0.125 in | 6.42 ft² | 12.83 ft² | 25.67 ft² | 38.50 ft² | 64.17 ft² |
| 0.25 in | 3.21 ft² | 6.42 ft² | 12.83 ft² | 19.25 ft² | 32.08 ft² |
| 0.5 in | 1.60 ft² | 3.21 ft² | 6.42 ft² | 9.63 ft² | 16.04 ft² |
| 1 in | 0.80 ft² | 1.60 ft² | 3.21 ft² | 4.81 ft² | 8.02 ft² |
Coverage chart: square metres covered, by coat thickness (millimetres) and amount of mixed epoxy (litres)
One coat, no waste allowance: the area is the volume divided by the thickness. Down the side is the coat thickness, across the top the amount of mixed epoxy, in the units named in the heading.
| Epoxy you have | |||||
|---|---|---|---|---|---|
| Thickness of one coat | 0.5 L | 1 L | 2 L | 5 L | 10 L |
| 1 mm | 0.50 m² | 1.00 m² | 2.00 m² | 5.00 m² | 10.00 m² |
| 2 mm | 0.25 m² | 0.50 m² | 1.00 m² | 2.50 m² | 5.00 m² |
| 3 mm | 0.17 m² | 0.33 m² | 0.67 m² | 1.67 m² | 3.33 m² |
| 5 mm | 0.10 m² | 0.20 m² | 0.40 m² | 1.00 m² | 2.00 m² |
| 10 mm | 0.05 m² | 0.10 m² | 0.20 m² | 0.50 m² | 1.00 m² |
River table chart: US gallons for a river 72 in long, by pour depth and average river width (inches)
Mixed epoxy for a river 72 in (6 ft) long, with a 10 percent waste allowance included. For another length, scale in proportion: a 36 in river needs half as much.
| Average river width | |||||
|---|---|---|---|---|---|
| Depth of the pour | 4 in | 6 in | 8 in | 10 in | 12 in |
| 1 in | 1.37 US gal | 2.06 US gal | 2.74 US gal | 3.43 US gal | 4.11 US gal |
| 1.5 in | 2.06 US gal | 3.09 US gal | 4.11 US gal | 5.14 US gal | 6.17 US gal |
| 2 in | 2.74 US gal | 4.11 US gal | 5.49 US gal | 6.86 US gal | 8.23 US gal |
| 2.5 in | 3.43 US gal | 5.14 US gal | 6.86 US gal | 8.57 US gal | 10.29 US gal |
| 3 in | 4.11 US gal | 6.17 US gal | 8.23 US gal | 10.29 US gal | 12.34 US gal |
Used by
- Epoxy resin volume calculatorEnter the size and depth of your mold, round form or river. You get the mixed epoxy to prepare, split into resin and hardener.
- Epoxy coverage calculatorEnter the surface, the thickness of one coat and the number of coats. You get the epoxy to mix, or the area that the epoxy you have will cover.
- Deep pour epoxy layer calculatorEnter the size and total depth of the pour and the deepest layer your product allows. You get the number of layers and the epoxy for each one.