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River table epoxy calculator

Rivers are never straight. Measure the width at evenly spaced marks along the length and EpoxyPlan adds up the true shape. Or use a simple rectangle for a quick estimate.

1River shape

in
Measure every
River width at each mark

Measure straight across, edge to edge, at each mark from one end. Decimals or fractions both work (6.5 or 6 1/2).

2Depth and buffer

in
Usually the slab thickness.
Waste buffer
Covers mixing cups, drips and wood soak-up.
Weight setting
g/mL
Clear epoxy is typically about 1.1 g/mL. Only used for the weight estimate.

3Check against a product

Optional

How the section method works

Between two marks, the river is treated as a trapezoid: the average of the two widths times the distance between them. Adding up every segment gives the river's area, and area times depth gives the volume. The last segment can be shorter than the others; its real length is used.

Closer marks follow curves more closely. 12 in (30 cm) spacing is fine for gentle rivers; use 6 in (15 cm) where the edge changes quickly.

Quick check by hand

A 60 in river measured every 12 in at 4, 6, 8, 6, 5 and 3 in wide has an area of 12 × (5 + 7 + 7 + 5.5 + 4) = 342 sq in. At 1 1/2 in deep that is 513 cubic inches, or 2.22 gal (231 cubic inches per gallon). With a 10% buffer, mix 2.44 gal.

Before you trust any number

  • Wood soaks up epoxy and forms can leak. Canadian Woodworking advises mixing extra for this.
  • Check your product's maximum depth per pour. If your depth is deeper, plan staged pours.
  • Mix by the product's own ratio. 2:1 by volume is not 2:1 by weight.