Most ruined resin orders were not caused by bad geometry. They were caused by unplanned waste, edge loss, or forgetting that the purchase quantity should be safer than the bare minimum.
Direct Answer
Choose a waste allowance separately from the raw geometry. For a raw 2 US gal pour, 8% adds 0.16 gal and 20% adds 0.40 gal. These are planning scenarios, not universal recommended percentages: use the loss observed on a comparable project and account separately for measured seal coat or edge work.
Takeaways
Order quantity = raw mixed volume × (1 + waste / 100). Entering 10% means adding a tenth of the raw volume, not buying another full kit. Apply the buffer before rounding to kit sizes. The table uses the same 2 gal cavity to show how the assumption affects the order; it does not rank the percentages as safe for every resin or substrate.
| Illustrative buffer | Extra mixed resin | Buffered total |
|---|---|---|
| 0% | 0 gal | 2.00 gal |
| 8% | 0.16 gal | 2.16 gal |
| 12% | 0.24 gal | 2.24 gal |
| 20% | 0.40 gal | 2.40 gal |
Record the amount mixed, the amount left in containers and any separately measured overfill or runoff on a comparable job. If 100 ml of a 1,000 ml batch never reaches the intended cavity, usable material is 900 ml. Replacing that loss requires 1,000 / 900 − 1 = 11.1% extra relative to the usable volume, not exactly 10%. The example explains the percentage bases; actual absorption and leaks may remain difficult to measure.
In the river tool, waste, seepage and the optional seal-coat estimate are added as percentage points to raw volume. With 12%, 8% and 5%, the factor is 1.25. If you calculate a seal coat as its own area-and-thickness quantity, turn off the estimated seal-coat option before adding that separate result. Likewise, do not add a second edge allowance without checking the coverage tool's breakdown. A leaking mold needs repair before a bigger allowance.
A reserve percentage changes the purchase plan, not the cavity geometry or the manufacturer's mix ratio. If raw volume is 1 L, 8% waste plus a separate 5% allowance gives 1.13 L when both are percentages of raw volume. Applying 5% to 1.08 L instead gives 1.134 L. The calculator states which additive convention it uses. To turn the reserve into kits for a floor, use the epoxy floor coverage calculator.
FAQ
No. It is the general tool's editable default. Your substrate, application and recorded loss should determine the working assumption.
No. Loss from a leak is not reliably bounded by the cavity's volume. Seal and test the mold before pouring.
Apply it to the project quantity first, then round up to usable mixed kit sizes. Show unused kit material separately from application waste.
Related Pages
Free epoxy volume calculator: enter length, width, and depth in inches or cm to see how much resin to pour in ounces, gallons, or liters, with waste and cost.
Estimate epoxy for river tables with quick mode, segment mode, seepage, seal-coat buffer, cost planning, and deep-pour recommendations.
Calculate epoxy for cracks, knots, and void fills with small-volume estimates, waste buffer, and unit conversion.
Estimate epoxy project cost from planned resin quantity, waste, and price input for river tables, deep pours, coatings, and other resin projects.
Reviewed · Calculation notes and corrections