Epoxy Pour Calculator: Estimate Resin Volume

Calculate epoxy pour volume by multiplying the area to cover by the pour depth, using matching units. Enter the surface length and width and the planned depth; the calculator returns the volume in cubic inches and US gallons, plus liters for metric planning.

Formula

For a flat, rectangular pour, volume equals surface area multiplied by depth:

V = L × W × D

• V is volume in cubic inches (in³) when all dimensions are in inches.
• L is length in inches.
• W is width in inches.
• D is average pour depth in inches.

To convert cubic inches to US liquid gallons, divide by 231. To convert US gallons to liters, multiply by 3.785411784. These are volume conversions; they do not change the amount of resin required. For metric dimensions, multiply length, width, and depth in centimeters to get cubic centimeters (cm³), then divide by 1,000 for liters. Keep all dimensions in one unit system before calculating.

Worked Example

Using the calculator’s default values—24 in long, 12 in wide, and 1 in deep:

1. Area = 24 × 12 = 288 in².
2. Volume = 288 × 1 = 288 in³.
3. US gallons = 288 ÷ 231 = 1.247…, which rounds to 1.247 US gal.
4. Liters = 1.247… × 3.785411784 = 4.720…, which rounds to 4.720 L.

The unrounded volume is 288 in³. The calculator’s cubic-inch output therefore displays 288.0 in³.

How to Measure a Pour

Measure the inside dimensions of the area that will actually hold resin, not the outside dimensions of a mold or frame. For a rectangular tabletop or tray, take the usable length and width. Measure depth from the intended bottom surface to the planned finished resin surface. If the base is uneven, measure at several points and use a reasonable average depth; a single depth measurement can underestimate the quantity where the pour is deeper.

This calculator assumes a level rectangular volume with constant depth. It is a practical estimate for a simple cavity, not a substitute for measuring a complicated shape. A circular pour needs a different area calculation, and irregular shapes may need to be divided into simpler rectangles or other geometric sections and added together.

From Volume to Resin and Hardener

The volume result estimates the total space to fill. It does not automatically determine the separate quantities of resin and hardener, because those depend on the product’s specified mixing ratio. Follow the ratio on the product instructions, including whether it is given by volume or by weight. A ratio by volume cannot be assumed to match the same numerical ratio by weight: the components may have different densities.

Also check the product’s permitted pour depth and the project’s layer plan. Some casting systems are designed for deeper pours than others, while many coating products are intended for thin layers. Dividing a deep fill into layers may be necessary, but the allowable depth, waiting time, and whether a later layer can be poured over a cured or partially cured layer are product-specific. Use the manufacturer’s technical directions rather than treating one general depth as suitable for every epoxy.

For example, a calculated 4.72 L describes the approximate cavity volume in the default example. It does not mean to combine 4.72 L of resin with an additional amount of hardener. Whether the mixed total should equal that cavity volume depends on how the manufacturer defines its ratio and on practical losses, such as material left in the mixing container.

Allowances, Shapes, and Limits

Real projects can use slightly more or less material than the geometric estimate. Wood pores, cracks, seams, surface texture, leaks, and material retained in tools can affect consumption. Conversely, an object embedded in the pour displaces volume: if it occupies part of the cavity, the epoxy needed is less than the full cavity volume. For an irregular project, calculate the fillable space rather than the outer dimensions alone.

Do not add a large, automatic waste allowance without considering the project. A small reserve can be useful for measuring uncertainty and residue, but excess mixed epoxy may be unusable after its working time and must be handled according to its safety instructions. Calculate carefully, then use product guidance and a small test or staged plan when the shape or substrate makes the estimate uncertain.

• Use the same units for length, width, and depth.
• Measure the actual inside space, including any variation in depth.
• Subtract the volume of substantial objects that displace resin.
• Check whether the stated mixing ratio is by volume or by weight.
• Keep extra material and mixing plans within the product’s working and pour-depth limits.

Common Calculation Mistakes

A frequent error is multiplying measurements expressed in different units—for example, a width in feet and depth in inches. Convert first: 1 ft = 12 in, and 1 in = 2.54 cm. Another common mistake is using surface area alone. Area does not provide a volume until it is multiplied by depth. For a 288 in² surface poured 1 in deep, the volume is 288 in³; a 2 in depth doubles it to 576 in³.

Be precise about gallons, too. The conversion in this calculator is for US liquid gallons. A US gallon is not the same size as an imperial gallon. Finally, rounding too early can distort the result when you are converting between units or splitting a project into batches. Keep the unrounded value through the calculations and round the final display to a useful level.

Frequently Asked Questions

How do I calculate how much epoxy I need?
Multiply the area to be filled by the average depth to get volume. For a rectangle in inches, length × width × depth gives cubic inches; divide by 231 for US gallons or by 61.024 for approximate liters.

How much epoxy covers 1 square foot?
It depends on the pour depth. One square foot has 144 square inches, so a 1-inch-deep rectangular layer is 144 in³, or about 0.623 US gallon. A thinner coating uses proportionally less volume.

Should I measure epoxy by weight or volume?
Use the method and ratio specified for the epoxy system. If its ratio is by weight, use a scale and do not substitute a volume ratio; if it is by volume, measure the components volumetrically as directed.

Does the calculator include hardener?
The volume estimate represents the total space to fill, not a separate resin-only quantity. Use the product’s instructions to determine how much of each component makes the required mixed batch.

Can I use this for a round mold?
Not directly, because the calculator assumes a rectangular footprint. For a cylindrical mold, use π × radius² × depth, with all dimensions in the same units, then convert the resulting cubic units to gallons or liters.

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in length | Surface length | in | 24 | 0
in width | Surface width | in | 12 | 0
in depth | Pour depth | in | 1 | 0
out volume | Epoxy volume | US gal | length * width * depth / 231 | 3
out liters | Epoxy volume | L | volume * 3.785411784 | 3
out cubic_inches | Epoxy volume | in³ | length * width * depth | 1