Epoxy Resin Calculator (River Table, Deep Pour and Table Top)

Running out of epoxy halfway through a pour is expensive, and so is a gallon left over. This calculator works out the volume of a river table, a rectangular or round mold, or a flood coat over a table top, adds an allowance for leaks, sanding and what sticks to the mixing buckets, and splits the total into resin and hardener at your product’s mix ratio. It also gives the weight, useful when the kit is sold by weight or you mix on a scale, and how many separate pours the depth needs at the label’s maximum layer thickness.

Epoxy resin calculator

How it works

The volume is simple geometry, converted to liquid measures:

river or rectangle: length × width × depth; round: π × diameter² ÷ 4 × depth
1 US gallon = 231 cubic inches = 128 fl oz = 3.785 litres
resin = total × ratio ÷ (ratio + 1); hardener = total ÷ (ratio + 1), for a mix ratio by volume of ratio : 1
weight = gallons × the mixed weight per gallon from the data sheet
number of pours = depth ÷ maximum depth per pour, rounded up

The default weight, 9.05 lb per gallon, comes from one deep-pour casting epoxy’s technical data sheet: resin 9.52 lb/gal and hardener 8.10 lb/gal, mixed 2 : 1 by volume. Other products are close to this but not the same, so enter your own figure. For a river, measure the gap every foot or so along the slab and use the average width.

Worked example

A 6 ft river table with a gap averaging 6 in wide and 1.5 in deep, a 2 : 1 epoxy rated for 3/4 in per pour, and 10% extra:

Units: Inches, gallons and pounds
Pour: River table or slab gap (length x average width)
Depth (or coat thickness): 1.5 in
Extra for leaks, sanding and mixing cups: 10%
Mix ratio by volume (resin : hardener): 2 : 1
Mixed epoxy weight: 9.05 lb/gal
Maximum depth per pour: 0.75 in

The calculator gives:

Mixed epoxy to buy: 3.09 gal (395 fl oz)
In litres: 11.68 L
Resin (part A): 2.06 gal (263 fl oz)
Hardener (part B): 1.03 gal (132 fl oz)
Weight of mixed epoxy: 27.9 lb (12.7 kg)
Volume without the extra: 2.81 gal (359 fl oz)
Pours at 0.75 in or less: 2 pours of about 1.54 gal (197 fl oz) each

The gap holds 648 cubic inches, 2.8 gallons; with 10% extra buy about 3.1 gallons (395 fl oz), which is 2.06 gallons of resin and 1.03 of hardener. It will weigh about 28 lb mixed. At 3/4 in per pour that is two pours of about 1.5 gallons each, with the wait between them that the label gives. Seal the slab edges and the gaps under the form first: end grain and bark pockets soak up more than you expect.

Epoxy needed per square foot, by depth

Depth	Cubic inches	Gallons	Fluid ounces	Litres	Square feet per gallon
1/8 in	18	0.078	10	0.29	12.8
1/4 in	36	0.156	19.9	0.59	6.4
1/2 in	72	0.312	39.9	1.18	3.2
3/4 in	108	0.468	59.8	1.77	2.1
1 in	144	0.623	79.8	2.36	1.6
1-1/2 in	216	0.935	119.7	3.54	1.1
2 in	288	1.247	159.6	4.72	0.8

One square foot = 144 square inches. No allowance for waste is included in this table.

Notes and limits

Pour no deeper than the label allows. Thick pours trap the heat the epoxy gives off as it cures; one maker’s sheet notes a colour shift from that heat in thick pours. One maker’s instructions also advise against pours thinner than 1/2 in for its casting resin, because very thin layers cure slowly.
Mix ratio by volume and by weight are different numbers. A 2 : 1 by volume product mixes about 100 : 44 by weight when the hardener is lighter than the resin. Use the ratio the label gives for the way you measure.
Acclimate the slab and the epoxy to the room (about 70 to 80 °F) for a day before pouring; cold epoxy thickens and holds bubbles.
A seal coat on the wood first stops air rising out of the grain into the pour. Allow a little epoxy for it.
To estimate the weight of the finished table, add the wood from the wood weight calculator to the epoxy weight shown here.

Frequently asked questions

How much epoxy do I need for a river table?

Multiply the length, the average width of the river and the depth in inches, divide by 231 for gallons, and add about 10%. A 72 × 6 × 1.5 in river needs about 3.1 gallons.

How much epoxy for a table top coat?

A 1/8 in flood coat takes 18 cubic inches per square foot, about 10 fl oz. A 4 × 2 ft table top needs about 0.62 gallons, or 0.69 gallons with 10% extra.

How much does a gallon of epoxy weigh?

A little more than water (8.34 lb/gal). One casting epoxy’s data sheet gives 9.52 lb/gal for the resin and 8.10 for the hardener, about 9.05 lb/gal mixed at 2 : 1. Check the sheet for your product.

How deep can I pour epoxy in one go?

Only as deep as the product label says. One maker rates its deep-pour river resin for up to 1.5 in per pour and recommends 1/2 to 3/4 in layers of its void-filling resin for the lightest colour; table-top coating epoxies are meant for much thinner coats. Deeper sections need several pours.

How many ounces of epoxy per square foot at 1/4 inch?

About 20 fl oz (0.156 gallons): 144 × 0.25 = 36 cubic inches.

Sources

Last reviewed: 25 October 2026. The calculation is covered by automated tests with known answers taken from the sources above. Found an error? Please let us know.