This guide teaches the page-selection and measurement logic behind the calculators. It is for users who want to understand the method before trusting a number.
Direct Answer
For a rectangular cavity, use inside length × width × depth in one unit system. Divide cubic inches by 231 for US gallons, or cubic centimeters by 1,000 for liters, then add measured extra work and a chosen loss allowance. Keep the order quantity separate from the permitted batch or layer size.
Takeaways
A rectangle, circle, sphere, cylinder, floor coating, and live-edge river channel do not share the same calculation model. That is why this site uses a separate calculator for each project type.
For 48 × 18 × 1.25 in, volume = 1,080 in³. That is 4.675 US gal or 17.698 L. The same dimensions are 121.92 × 45.72 × 3.175 cm: their product is 17,698.029 cm³, and dividing by 1,000 gives the same liters. With a selected 8% allowance, the order is 5.049 gal or 19.114 L. Small differences in displayed decimals come from rounding, not a different model.
| Step | Calculation |
|---|---|
| Inside volume | 48 × 18 × 1.25 = 1,080 in³ |
| US gallons | 1,080 / 231 = 4.675 |
| 8% example allowance | 4.675 × 1.08 = 5.049 gal |
| Purchase | Round up to usable mixed kit sizes after choosing the buffer |
For a circular cavity use π × (diameter / 2)² × depth, not diameter × diameter × depth. A 4 in diameter cavity 1/4 in deep holds π in³, or about 1.74 US fl oz. For several independent pockets, calculate each and add the volumes. Subtract occupied inserts only when their displaced volume can be measured; use segment calculations for an irregular river.
Write the unit beside every measurement before multiplying. For a metric cavity, cm × cm × cm gives mL; for inch measurements, divide in³ by 231 for US gallons. Add named allowances to the raw quantity, then round up to the mixed yield of a complete kit. Keep the kit order and the permitted batch size separate.
FAQ
For simple rectangular volume, use length times width times depth. For coverage, use area times thickness. For floors, use area, coats, and coverage rate.
Because the project type changes the variables. Floors, flood coats, river tables, and molds need different assumptions.
Add waste after raw volume or coverage is calculated, then adjust the buffer for the project risk.
Related Pages
Calculate deep pour epoxy volume, staged lift count, waste, and cost for thick casting projects and resin pours that cannot be treated like a surface coat.
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.
Enter square feet (or m²) and coat thickness to see how many gallons of epoxy you need, with edge runoff, waste, and cost for tabletops, bar tops, and countertops.
Estimate epoxy for river tables with quick mode, segment mode, seepage, seal-coat buffer, cost planning, and deep-pour recommendations.
Choose epoxy kit size after calculating project quantity, waste, Part A/B split, unit conversion, and product-specific limits.
Reviewed · Calculation notes and corrections