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River Table Epoxy Calculator
Estimate the epoxy for the river channel between two live-edge slabs. Instead of measuring a wavy edge exactly, estimate what percentage of the tabletop area the river occupies.
Formula
V (in³) = length × width × depth × (gap% ÷ 100)
V_total = V × (1 + waste% ÷ 100)
Gallons = V_total ÷ 231How to estimate the gap percentage
Lay the slabs in the form and measure the river width at several evenly spaced points along the length (for example every 6 inches). Average those widths and divide by the table width. If the average river width is 9 inches on a 36 inch wide table, the gap is 9 ÷ 36 = 25%.
Remember to include epoxy that will soak into or flow under bark inclusions, cracks and knots, and the extra thickness if you plan to flatten the top after curing. That is why a waste allowance of 10–20% is sensible for river tables.
Worked example
72 × 36 × 1.5 in = 3,888 in³ of total tabletop volume. 25% of that is 972 in³, which is about 4.21 gallons. With 10% extra you would plan for roughly 4.6 gallons. Read our guide How much epoxy for a river table for the full method.
River pours are usually thick, so check your product's maximum pour depth and use the deep pour calculator to plan layers.
Unit conversions used
- 1 US gallon = 231 in³ = 128 US fl oz
- 1 US fl oz = 1.8047 in³ = 29.5735 ml
- 1 in³ = 16.387 ml; 1 ft³ = 1,728 in³ ≈ 7.48 gal
- Weight = volume (cm³) × density. Many mixed epoxies are roughly 1.05–1.2 g/cm³; the default 1.1 is an approximation — check your product's technical data sheet and edit the field.
Frequently asked questions
How many gallons of epoxy for a river table?
Multiply length × width × thickness in inches, multiply by the river's share of the area, then divide by 231. A 72 × 36 × 1.5 inch table with a 25% river needs about 4.2 gallons before waste.
How do I measure a river gap with irregular edges?
Measure the gap width at regular intervals, average them, and divide by the table width to get the gap percentage.
Should I add extra epoxy for a river table?
Yes. Epoxy seeps into cracks, knots and under bark, and some is lost to the form and mixing cups. 10–20% extra is a common buffer.
Can I pour a river table in one layer?
Only if your epoxy is rated for that depth. Deep pour epoxies are formulated for thick pours; tabletop epoxies usually are not. Follow the manufacturer's maximum depth.