Use the below formula (In Inches): This tells you the exact amount you in need in LITRES(Length) x (Width) x (Thickness) = X Divide this total (X) by 61 = Total amount of epoxy needed to fill the areaWe always add 10 - 15 % more to compensate for any epoxy that might soak into the grain of the wood, leak or spill. It is also good to have extra to top off the pour if it sinks down within the first 8 hours (Which is common when is soaks into the wood grain).