How much epoxy do I need for a river table?

Length times average gap times depth, in cubic inches, divided by 231. A 6' river averaging 6" wide and poured 1 1/2" deep holds 648 cubic inches, which is 2.81 gallons; with 10% for the wood soaking some up and what stays in the bucket, mix 3.09. Measure the gap every foot or so and average it — a river is never one width, and the widest point is not the one to use.

How many square feet does a gallon of epoxy cover?

A US gallon is exactly 231 cubic inches, so a gallon poured 1" deep covers 231 square inches — 1.60 square feet. Half an inch deep it covers twice that, and a 1/8" flood coat on a tabletop about eight times that. That is the whole of the geometry; the allowance for absorption and spills is the part that is a judgement.

Why does deep pour epoxy have a maximum pour depth?

Epoxy cures by a reaction that gives off heat, and a thick pour cannot shed that heat fast enough — past the depth the maker rates it for, it can crack, yellow, or boil with bubbles. The figure is on the label and runs from about 1/4" for a tabletop coating to several inches for a slow deep-pour resin. A 2" river in a resin rated for 1" a pour goes in as 2 pours of 1", each left for the time the label gives before the next.

What does a 2:1 epoxy mix ratio mean?

Two parts resin (A) to one part hardener (B), by volume unless the kit says by weight. A one-gallon pour at 2:1 is 2.67 quarts of A and 1.33 of B. The ratio is set by the chemistry, not by preference: extra hardener does not cure it faster, it leaves the pour soft and tacky. Kits sold by weight have parts of different densities, so a weight ratio cannot be measured out by volume.

Epoxy calculator for river tables and resin pours

Enter the pour — a river between two slabs, a rectangle or a circle — and its depth. This works out the resin in gallons, quarts, litres and ounces, splits it into part A and part B by the kit's ratio, and says how many pours the label's maximum depth allows.

Shape

Length

Average gap

Measure it every foot and average

Pour depth

= 1.5"

Max depth per pour

On the product label

Advanced settings10% extra · mix 1:1 A to B

Absorption and waste

10% is the usual allowance; more for punky or spalted wood

Mix ratio, by volume

Part A

parts

Part B

parts

Mix this much epoxy

3.09gallons

Quarts

12.3 qt

Litres

11.7 L

Fluid ounces

395 fl oz

Part A

1.54 gal · 6.2 qt

Part B

1.54 gal · 6.2 qt

Pours

2 × 3/4"

Where the number comes from

Plan area3.00 sq ft: 432 sq in
Volume of the pour2.81 gal at 231 cubic inches to the US gallon: 648 cu in
Plus 10% for absorption and waste: 3.09 gal
Each of 2 pours3/4" deep, mixed as one batch: 1.54 gal

Before the first pour

Seal the wood with a thin coat first — it stops the end grain bleeding bubbles into the pour, and it is part of what the allowance covers. Wait the time the label gives between pours: too soon and the heat of two layers adds up, too late and the second layer needs sanding to bond.

The mix ratio here is by volume. If your kit gives a ratio by weight, measure by weight on a scale instead — the two parts are not the same density, so the numbers are not interchangeable.

Where to buy this

3.09 gal of epoxy, 2 poursHome Depot Lowe's

This searches the product, not a kit size we worked out for you. Kits are sold as A and B together, so check the combined volume on the box against the total here.

Plain search links, nothing sponsored. Prices and stock are the shop's, and a local lumberyard will usually beat both on solid stock.

Worked example: a river table

A river 72" long with a gap averaging 6", poured 1 1/2" deep, holds 648 cubic inches of resin — 2.81 gallons at 231 cubic inches to the US gallon.

With 10% for absorption and waste, mix 3.09 gallons (12.3 quarts, 11.7 litres): 1.54 of part A and 1.54 of part B at 1:1.

The label allows 1" a pour, so it goes in as 2 pours of 3/4", 1.54 gallons each.

Epoxy to mix: 3.09 gallons
Part A: 1.54 gallons
Part B: 1.54 gallons
Pours: 2 × 3/4"

These are the figures the calculator above opens on. Change any field and it works the same problem for your numbers.

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About epoxy pours

How much epoxy do I need for a river table?: Length times average gap times depth, in cubic inches, divided by 231. A 6' river averaging 6" wide and poured 1 1/2" deep holds 648 cubic inches, which is 2.81 gallons; with 10% for the wood soaking some up and what stays in the bucket, mix 3.09. Measure the gap every foot or so and average it — a river is never one width, and the widest point is not the one to use.
How many square feet does a gallon of epoxy cover?: A US gallon is exactly 231 cubic inches, so a gallon poured 1" deep covers 231 square inches — 1.60 square feet. Half an inch deep it covers twice that, and a 1/8" flood coat on a tabletop about eight times that. That is the whole of the geometry; the allowance for absorption and spills is the part that is a judgement.
Why does deep pour epoxy have a maximum pour depth?: Epoxy cures by a reaction that gives off heat, and a thick pour cannot shed that heat fast enough — past the depth the maker rates it for, it can crack, yellow, or boil with bubbles. The figure is on the label and runs from about 1/4" for a tabletop coating to several inches for a slow deep-pour resin. A 2" river in a resin rated for 1" a pour goes in as 2 pours of 1", each left for the time the label gives before the next.
What does a 2:1 epoxy mix ratio mean?: Two parts resin (A) to one part hardener (B), by volume unless the kit says by weight. A one-gallon pour at 2:1 is 2.67 quarts of A and 1.33 of B. The ratio is set by the chemistry, not by preference: extra hardener does not cure it faster, it leaves the pour soft and tacky. Kits sold by weight have parts of different densities, so a weight ratio cannot be measured out by volume.