How to use the river table resin calculator
- Enter the finished table length and width.
- Measure the average river width between the slabs and pick a river shape.
- Enter the slab thickness — the depth of resin you will pour — and the maximum pour depth from your resin’s label.
- Choose whether to add a flood coat, set an allowance for waste, and add the resin price if you want a cost.
The formula
River volume = Length × Average river width × Shape factor × Depth Flood coat = Length × Width × Coat thickness Total = (River + Flood coat) × (1 + Waste %) US gallons = cubic inches ÷ 231 Litres = cm³ ÷ 1,000 Pours = Depth ÷ Max depth per pour (rounded up)
Worked example
A 72 × 36 in dining table with a 10 in wide river, 2 in thick, plus a ⅛ in flood coat and 15% extra:
- River = 72 × 10 × 2 = 1,440 in³ = 6.23 gal
- Flood coat = 72 × 36 × 0.125 = 324 in³ = 1.40 gal
- Total = 1,764 in³ × 1.15 = 8.78 gal (33.2 L) — a 2:1 kit would be about 5.9 gal of resin and 2.9 gal of hardener
Resin needed per foot of river (2 in deep)
| River width | Per foot of length | 6 ft table | 8 ft table |
|---|---|---|---|
| 4 in | 0.42 gal | 2.5 gal | 3.3 gal |
| 6 in | 0.62 gal | 3.7 gal | 5.0 gal |
| 8 in | 0.83 gal | 5.0 gal | 6.6 gal |
| 10 in | 1.04 gal | 6.2 gal | 8.3 gal |
| 12 in | 1.25 gal | 7.5 gal | 10.0 gal |
Before waste and flood coat. For a 1½ in slab, multiply by 0.75.
Choosing the right epoxy
- Deep-pour (casting) epoxy cures slowly so heat can escape — essential for the river itself. It may take several days to cure fully.
- Tabletop (coating) epoxy is thicker and cures faster, but can only be poured about ⅛–¼ in at a time. Use it for seal coats and flood coats only.
- Check the mix ratio (1:1, 2:1 or 3:1 by volume or weight) and use the resin mixing ratio calculator to split the total.
Tips for a successful pour
- Dry wood: aim for about 6–10% moisture content, or moisture can cause bubbles and cracks.
- Seal the wood first with a thin coat of resin to stop air escaping from the wood into the pour.
- Build a leak-proof mould from melamine or HDPE with silicone caulk at every seam, and level it carefully.
- Mind the temperature: most resins like 70–80 °F (21–27 °C). Cold resin cures slowly and traps bubbles; hot resin can overheat.
- Mix thoroughly, scraping the sides and bottom, and pour slowly. A heat gun or torch passed quickly over the surface pops bubbles.
- Plan for sanding: the top is usually flattened with a router sled and sanded, so pour a little higher than the final thickness.