How much epoxy do I need?
Type the size of the surface and how thick the epoxy should be. The epoxy calculator shows how much to mix in gallons, fluid ounces and litres, split into resin and hardener by your mix ratio.
- US gallons
- 0.686
Mix 0.686 gal (2.596 L) of epoxy: 43.9 fl oz of resin and 43.9 fl oz of hardener.
- Fluid ounces
- 87.8
- Litres
- 2.596
- Resin, fluid ounces
- 43.9
- Hardener, fluid ounces
- 43.9
- Resin, millilitres
- 1,298
- Hardener, millilitres
- 1,298
US gallons: 0.686. Mix 0.686 gal (2.596 L) of epoxy: 43.9 fl oz of resin and 43.9 fl oz of hardener.
How much is resin and how much hardener?
How to calculate
Computes the volume of epoxy resin to coat or pour a rectangular or round surface to a thickness, with extra for waste, in gallons, fluid ounces and litres, and how much resin and hardener to mix.
Example with the default inputs (Shape Rectangle, Length 4 ft, Width 2 ft, Thickness 0.125 in, Extra for waste 10%, Resin parts 1, Hardener parts 1): Mix 0.686 gal (2.596 L) of epoxy: 43.9 fl oz of resin and 43.9 fl oz of hardener.
Method: Volume = length × width (or π × diameter² ÷ 4) × thickness × (1 + extra ÷ 100); resin = volume × a ÷ (a + b); hardener = volume × b ÷ (a + b), for an a:b mix by volume.
- The epoxy spreads to an even thickness over the whole surface; a rough or porous surface soaks up more.
- Extra for waste is 10% by default, for drips over the edges and resin left in the mixing cup.
- The mix ratio is by volume. For an epoxy mixed by weight, use the maker’s weights instead.
Worked examples
Each example is checked against the calculator on every build.
- Shape Rectangle, Length 4 ft, Width 2 ft, Thickness 0.125 in, Extra for waste 10%, Resin parts 1, Hardener parts 1 gives US gallons 0.685714, Fluid ounces 87.771429, Litres 2.595711, Resin, fluid ounces 43.885714, Resin, millilitres 1,297.855469.Source: NIST Handbook 44, Appendix C (1 US gallon = 231 in³ = 128 fl oz = 3.785411784 L)
- Shape Rectangle, Length 3.281 ft, Width 1.64 ft, Thickness 0.07874 in, Extra for waste 0%, Resin parts 2, Hardener parts 1 gives Litres 1, Resin, millilitres 666.666667, Hardener, millilitres 333.333333, US gallons 0.264172.Source: NIST Handbook 44, Appendix C (1 L = 0.001 m³)
- Shape Circle, Diameter 3 ft, Thickness 0.25 in, Extra for waste 0%, Resin parts 1, Hardener parts 1 gives US gallons 1.101597.Source: NIST Handbook 44, Appendix C (1 gal = 231 in³)
How it works
The epoxy layer is a thin box (or a thin disc for a round surface):
- Rectangle: volume = length × width × thickness
- Circle: volume = π × diameter² ÷ 4 × thickness
- Epoxy to mix = volume × (1 + extra ÷ 100)
- For a mix ratio of a parts resin to b parts hardener by volume: resin = epoxy × a ÷ (a + b), hardener = epoxy × b ÷ (a + b)
The results show in US gallons (1 gal = 231 in³ = 3.785411784 L), US fluid ounces (128 to the gallon), litres and millilitres, all exact conversions.
Exact arithmetic. Each measurement is read as the exact decimal you typed, in the unit you typed it in (1/8 in is exactly 0.125 in, and 3 mm is exactly 0.003 m). The page stores a length as a number in metres and reads it back as the decimal with the fewest significant digits, in one of the box's units, that gives the same stored number; a feet-and-inches pair counts by its value in inches (12 ft 6 in counts as 150, and 426.72 cm, exactly 14 ft, stays 426.72 cm), and on a tie the unit listed first in the box's unit menu wins. Every step for a rectangle is exact; a circle uses π.
Rounding. Gallons and litres show with at most 3 decimals, fluid ounces with 1, millilitres as whole numbers, each rounded half up from its exact value, with trailing zeros left off.
Assumptions
- The epoxy spreads to an even thickness; the surface does not soak it up.
- The extra for waste is 10% by default, from 0% to 100%.
- The mix ratio is by volume. Each part is more than 0 and at most 100.
- Lengths are more than 0 and at most 1,000 m; the thickness is more than 0 and at most 1 m.
Worked examples by hand
A 4 × 2 ft table top, 1/8 in coat, 10% extra, 1:1. 48 × 24 × 0.125 = 144 in³; × 1.1 = 158.4 in³. 158.4 ÷ 231 = 0.686 gal, which is 0.686 × 128 = 87.8 fl oz or 2.596 L. Half is resin: 43.9 fl oz (1,298 mL), and half is hardener.
A 100 × 50 cm board, 2 mm thick, no extra, 2:1. 100 × 50 × 0.2 = 1,000 cm³ = 1 L (0.264 gal). Resin 2/3 of it: 667 mL; hardener 1/3: 333 mL.
A round table 3 ft (36 in) across, 1/4 in pour, no extra. π × 36² ÷ 4 × 0.25 = 254.47 in³; 254.47 ÷ 231 = 1.102 gal.
Other questions people ask
How do I calculate how much epoxy I need?
Multiply the length by the width by the thickness to get the volume, in one unit. A 48 × 24 in table top with a 1/8 in coat needs 48 × 24 × 0.125 = 144 cubic inches. There are 231 cubic inches in a US gallon, so that is 0.62 gallon, or 79.8 fl oz. Add about 10% for drips and the resin left in the cup.
How much epoxy do I need for a river table?
Measure the river (the gap between the slabs) as a rectangle, or several rectangles, and use the full pour depth as the thickness. A river 72 in long, 6 in wide and 1.5 in deep holds 72 × 6 × 1.5 = 648 in³, which is 2.81 gallons before waste. Deep pours need an epoxy made for thick layers.
How thick should an epoxy coat be?
Many table-top epoxies self-level to about 1/8 in (3 mm) per coat, so 1/8 in is the default here. Deep-pour casting resins can be poured much thicker in one go. Check the maximum pour depth on your epoxy’s label.
What does a 1:1 or 2:1 mix ratio mean?
It is how many parts of resin go with how many parts of hardener, by volume. For 1:1, half the mix is resin and half is hardener. For 2:1, two-thirds is resin and one-third is hardener: 1 litre of 2:1 epoxy is 666.7 mL of resin and 333.3 mL of hardener.
How many fluid ounces are in a gallon of epoxy?
A US gallon is 128 US fluid ounces, 231 cubic inches, or exactly 3.785411784 litres. A “1 gallon kit” of 1:1 epoxy usually means half a gallon of resin and half a gallon of hardener.
Why add extra for waste?
Some epoxy runs over the edges, some stays in the mixing cup and on the spreader, and a porous surface soaks some up. The calculator adds 10% by default; set it to 0% for the layer volume alone.