River table epoxy calculator
Measure your river at a few points and get the whole plan: how much deep pour epoxy, how many layers, the seal and flood coats, and the kits to buy.
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How it is calculated
Deep pour. A river is never the same width all the way along, so the tool averages your width measurements. Volume is slab length x average width x depth, in cubic inches. Your extra allowance is added on top, because epoxy seeps around the form, clings to mixing cups and gets planed off afterwards.
Layers. Deep pour epoxy can only go down so thick in one pour before it overheats. The tool divides the depth by the maximum pour depth on your label and rounds up, then splits the depth evenly across that many layers.
Seal coat. Raw wood releases air into fresh epoxy. A thin brushed coat of table top epoxy on both river edges stops that. The tool allows a 1/32 in coat over both edges, which is a small amount.
Flood coat. After flattening, many makers pour a final coat over the whole top: length x overall table width x coat thickness.
Units and kits. 231 cubic inches make one US gallon (128 fl oz, 3.785 L). Kit suggestions use the fewest containers from common mixed sizes: 1 qt, 1/2 gal, 1 gal, 1.5 gal and 3 gal. Weight assumes a typical mixed epoxy of about 9.2 lb per gallon (1.1 g/ml).
Worked example
A 72 in slab with river widths of 6, 8, 5 and 7 in averages 6.5 in. At 1.5 in deep that is 72 x 6.5 x 1.5 = 702 cubic inches, plus 10 percent = 772 cubic inches, or 3.34 gallons (428 fl oz, 12.65 L) of deep pour epoxy.
The label allows 1 in per pour, so the river goes in 2 layers of 0.75 in, 1.67 gallons each. Buy 1 x 3 gal kit + 1 x 1/2 gal kit.
Sealing both river edges takes about 4 fl oz. A 1/8 in flood coat over the 72 x 36 in top takes 1.54 gallons. That is 1.58 gallons of table top epoxy: buy 1 x 1.5 gal kit + 1 x 1 qt kit. The deep pour alone weighs about 31 lb.
Epoxy gets hot as it cures. Pouring deeper than your label allows can crack, cloud or yellow the resin, and very large masses can overheat. Work with good ventilation and nitrile gloves, and follow your product's safety data sheet.
Common questions
- How much epoxy do I need for a river table?
- Multiply the slab length by the average river width and the river depth to get cubic inches, then divide by 231 for gallons. A 6 ft river averaging 6 in wide and 1.5 in deep holds about 2.8 gallons before any allowance. Add 10 to 15 percent for leaks and residue, plus table top epoxy for the seal and flood coats.
- How many pours does a river table need?
- Divide the river depth by the maximum pour depth on your deep pour epoxy's label and round up. Many deep pour products allow 1 to 2 in per layer and a few allow more. A 2 in river with a 1 in limit needs two layers.
- Do I need a seal coat before the deep pour?
- Most manufacturers recommend it. Wood is full of air, and as fresh epoxy soaks in, that air comes out as bubbles trapped in the river. A thin brushed coat of table top epoxy on the river edges, allowed to cure, seals them first.
- Why does the calculator add extra?
- Some epoxy always escapes: it seeps under the slabs and around the form, stays in the mixing cups, and gets planed or sanded off when you flatten the top. Running short mid-pour is far worse than having a cup left over, so 10 to 15 percent is a sensible allowance.
- Can I use table top epoxy for the river?
- Only for very shallow rivers within its limit, which is usually about 1/8 to 1/4 in per coat. Table top epoxy cures fast and gets hot in thick pours. Deep pour epoxy cures slowly so it can go down in thick layers. See the guide to deep pour vs table top epoxy.
Related tools and guides
WoodworkingCalc results are careful estimates. Products differ, so use the coverage, mix ratio and maximum pour depth printed on your own product label, and check the numbers against your project before you mix or buy.