Resin is too expensive to guess. This works out the true volume of a river channel or slab pour, adds a waste allowance you control, converts to the litres or gallons on the tin, and prices the pour — with the geometry drawn so you can check it against the real slab.
Notes
How the river channel is estimated
The channel is measured as an average width times length times depth. A live-edge channel is irregular — measure its width every 200 mm or so, average the readings, and use that. The diagram shows what the average-width rectangle looks like against your dimensions.
Why the waste allowance
Mixing losses, the film left in the bucket, overflow into the seal coat and absorption into the wood typically eat 5 to 15 percent. Deep-pour epoxies on well-sealed wood waste less; first pours on thirsty timber waste more. It is an input, not a hidden markup.
Maximum pour depth
Every epoxy has a maximum depth per pour — exceed it and the pour overheats, yellows or cracks. That limit is on YOUR product's data sheet, not in this tool: enter it and the tool splits the volume into pours.
Litres, gallons, and board feet do not mix
Resin kits are sold by total volume of the two parts combined. The figure here is that combined volume — compare it directly to the kit size on the label.
What this does not do
It does not know your product's mixing ratio, pot life, or exotherm limits — read the data sheet. And it does not estimate seal coats for porous surfaces; add those to the waste allowance instead.