Epoxy Volume Calculator

Measure the space, not the bottle. This epoxy volume calculator works out how much mixed epoxy a project needs from its length, width and depth, or from the diameter of a round mould, then adds a waste buffer and splits the total into resin and hardener at your mix ratio. A second tab keeps the original weight conversion: enter a weighed amount and a density, and it returns the volume that batch will fill.

Quick Answer

How to use both modes: project size first, weight when you need it

Use the By project size tab before you buy or mix anything, and the By weight tab after a batch is already on the scale. Results stay hidden until you click Calculate, and switching tabs hides the previous result.

1. By project size, shape and unit: pick Rectangle or Round, then inches or centimetres. The form shows length and width for a rectangle, or a single diameter field for a round pour.
2. Enter the depth honestly: depth means the epoxy layer you will actually pour. A 3 inch river table poured in two layers still needs the full 3 inch volume across both batches.
3. Set the waste buffer and ratio: 10% is the pre-filled starting point. Choose the ratio printed on your product, and the result splits the buffered total into resin and hardener in litres, millilitres and fluid ounces.
4. Read the pre-waste line last: it shows the true pour volume before the buffer. If a supplier quotes coverage against a bare volume, that is the number to compare.
5. By weight: switch tabs, enter the weighed amount in grams, kilograms or pounds, add the density from the data sheet, and the tab returns the volume in cm³, mL, litres and fl oz. A 200 g batch at 1.2 g/cm³ fills 166.67 cm³.

One measuring habit saves most bad pours: measure the inside of the mould or channel, not the outside of the board. Timber thickness and mould walls are not epoxy space. If the shape is irregular, break it into rectangles on paper, run each one, and add the volumes, the same habit behind any honest estimate, whether the material is epoxy or soil in a fill volume calculator.

The volume formulas for rectangular and round pours

A rectangular pour is length multiplied by width multiplied by depth. A round pour is the area of the circle, pi times the radius squared, multiplied by the depth. Both give a volume in cubic units, which then converts to the litres, gallons and fluid ounces that epoxy is actually sold in.

The hand checks are worth memorising. One US gallon is exactly 231 cubic inches by definition, so a pour of 462 in³ is 2 gallons before any buffer. Fluid ounces follow from the same gallon: 128 fl oz per gallon means one fl oz is 1.8046875 in³, about 1.805 in³ as a rounded shop shortcut. Metric work is cleaner, because the litre system is built on the cubic centimetre: as the National Institute of Standards and Technology volume guide sets out, 1 cm³ is 1 mL and 1,000 cm³ is 1 L. If your dimensions are in feet, convert with the cu feet calculator first, then multiply cubic feet by 1,728 to return to cubic inches.

Mix ratios: how the resin and hardener split works

A mix ratio of 2:1 means two parts resin to one part hardener, three parts in total. The resin share is the total multiplied by 2 ÷ 3, and the hardener share is the total multiplied by 1 ÷ 3. The same pattern holds at every ratio this calculator offers: at 1:1 each part is half, at 3:1 the resin is three quarters, and at 5:1 the resin is five sixths.

Two cautions decide whether that tidy arithmetic survives contact with a real product. First, the ratio here is by volume, how most tabletop, casting and deep pour epoxies are labelled. The TotalBoat ThickSet deep pour product page, for example, lists a 1:1 mix ratio by volume (shown as 1A:1B) alongside its pour depth limits, while the Fathom product in the comparison table on the same page is listed at 2:1 by volume. A ratio by weight would be a different number, because resin and hardener do not weigh the same per litre, so do not convert a volume ratio into weights. Second, never borrow a ratio from a similar looking product: mixing a 2:1 product at 1:1 leaves unreacted hardener that stays soft or tacky. ArtResin makes the same point in its guide on how to measure resin and hardener: extra hardener does not speed up a cure, it prevents a proper one.

Worked splits, all from this calculator: 8 L at 3:1 is 6 L of resin and 2 L of hardener. The worked example at 2:1 turns 7.79 L into 5.19 L and 2.60 L. A small 1:1 art pour of 643.5 mL splits evenly, 321.8 mL per part, why 1:1 products suit beginners: the measuring cup does the ratio for you.

Waste buffer: how much extra to mix, by project type

The buffer covers what never reaches the project: the film left in the mixing cup and on the stir stick, epoxy that soaks into bare wood, drips over an edge, and the small test pour sensible makers do first. Guidance from Epoxyworks on how much epoxy a project takes makes the same point: coverage figures assume a clean rolled coat on a non-porous surface, and real workshop handling always consumes more.

• Sealed mould, simple shape: 5 to 10%. Silicone and melamine moulds release cleanly and absorb nothing, so losses are mostly cup residue.
• River tables and live edge wood: 10 to 15%. Bare wood drinks the first coat, and an irregular channel is easy to under-measure. A seal coat reduces the soak, but still comes out of the same bottles.
• Coating a porous or rough surface: 15 to 20%. The first flood coat disappears into grain, checks and voids. Running short mid-coat leaves a join line no sanding fully hides.
• First time with a new product: keep 10% as a floor whatever the project. Pot life and pour behaviour vary, and a second small batch mixed in a hurry is the most common cause of a soft patch.

Do not inflate the buffer to dodge measuring. A 40% allowance on an expensive deep pour kit is real money left curing in a cup, and leftover mixed epoxy cannot go back in the bottle. Measure carefully, buffer modestly, and keep a small unopened kit in reserve for big pours instead.

Pour depth reference: coating epoxy is not casting epoxy

Depth decides both the volume and which product family can safely pour it. A coating epoxy poured too deep traps the heat of its own cure, and the result can be a cracked, yellowed or foaming layer. A deep pour product poured as a thin coat can take days to harden, because it is formulated to cure slowly in a large mass. The bands below are typical manufacturer ranges; your product sheet always wins.

The coating habit is documented in the WEST SYSTEM barrier coating instructions: a minimum of two coats for a moisture barrier, three if the surface will be sanded, building to roughly 20 mils across as many as six coats. Epoxyworks testing of epoxy on vertical surfaces likewise works in films of 2 to 4 mils. Thin coats in layers, not one heroic pour, is the professional pattern for coatings.

Worked example: a 24 by 12 inch river table pour, 1.5 inches deep

A maker is filling the channel of a small river table. The open channel measures 24 inches long and 12 inches wide, and the pour will be 1.5 inches deep. The product is a 2:1 deep pour epoxy, and the maker allows 10% for waste. Every number below is this calculator’s own output for the pre-filled inputs.

• Raw volume = 24 × 12 × 1.5 = 432 in³
• In metric = 432 × 16.387064 = 7,079.21 mL (about 7.08 L)
• Hand check in gallons = 432 ÷ 231 = 1.870 gal before the buffer
• With 10% waste = 475.2 in³ = 7,787.13 mL, shown as 7.79 L
• Total in US units = 2.057 gal and 263.3 fl oz
• Resin at 2:1 = 7.79 × 2 ÷ 3 = 5.19 L (5,191.42 mL, 175.5 fl oz)
• Hardener at 2:1 = 7.79 × 1 ÷ 3 = 2.60 L (2,595.71 mL, 87.8 fl oz)

Buying follows from the split, not the total. Kits are sold as combined volume, so a 2 gallon kit covers this pour with a little spare, while a 1.5 gallon kit does not, even though 1.5 gallons sounds close to the 1.87 gallon raw figure. The buffer is what pushes the job over the smaller kit, exactly the shortfall it exists to reveal before the pour starts. For a rectangular blank of a different size, the same logic drives the box volume calculator, and the gallons to ounces calculator handles kit-size conversions in the other direction.

Converting between units without losing the pour

Epoxy is sold in litres in most of the world and in gallons and fluid ounces in the US, while moulds are measured in inches or centimetres. Most quantity mistakes are conversion mistakes, so keep the chain short: volume in one cubic unit, convert once, then split.

• Cubic inches to litres: multiply by 16.387064 to get mL, then divide by 1,000. A 100 in³ pour is 1,638.71 mL, or 1.64 L.
• Cubic centimetres: already millilitres. A 60 cm × 30 cm × 4 cm mould is 7,200 cm³, which is 7.2 L before any buffer.
• Gallons and fluid ounces: divide cubic inches by 231 for gallons and by about 1.805 for fluid ounces (exact divisor 1.8046875). Both come from the same defined gallon, so the answers always agree: gallons × 128 equals fluid ounces.
• Round pours in metric: a 25 cm diameter mould at 2 cm deep is pi × 12.5² × 2 = 981.75 cm³, just under a litre.

Round at the end, not in the middle. Rounding the raw volume to a tidy litre before the buffer and ratio compounds small errors in the direction that leaves a pour short. The calculator keeps full precision internally and rounds only the display.

What competing calculators miss

The main rival tools size a pour well, and each stops one step short of a complete answer:

• MiniWebTool: the strongest rival, with rectangle and round modes, a waste buffer, ratio split and conversions. It adds a cost estimate, but presents the split without explaining volume ratio against weight ratio, the confusion that ruins real batches.
• CalculatorsHub: works from surface area times thickness and splits by ratio, but an area entry hides the depth decision: two pours with the same area and different depths are different products, not just different volumes.
• SuperEpoxySystems: clean separate rectangle and round calculators, but the two shapes live as separate tools and there is no weight based check for a batch already mixed or weighed.
• Craft Resin: sound shape formulas with a thickness guide, aimed at its own product range, so the ratio choices stop at what that range sells.
• The gap this page fills: dimension sizing for both shapes in inches or centimetres, the waste buffer applied before the split, volume ratio splits at 1:1, 2:1, 3:1 and 5:1, totals in litres, gallons and fluid ounces at once, plus the original weight to volume mode kept as a second tab for stock and leftovers.

When the weight mode is the right one

The By weight tab answers the reverse question: not how much to mix, but how far a weighed amount goes. It earns its place in four everyday situations. A supplier sells resin by weight, so the volume has to be recovered before it can be compared with a pour. A part-used bottle goes on the scale to check whether enough remains for a small job. A maker who mixes by weight, as many prefer for accuracy on small batches, needs the volume to compare against a mould. And a leftover batch gets weighed before being offered to another project, so its usable volume is known rather than guessed.

The maths is one division: volume equals weight divided by density. At the pre-filled values, 200 g ÷ 1.2 g/cm³ = 166.67 cm³, which is also 166.67 mL, 0.167 L or 5.64 fl oz. Density is the input to respect: 1 kg at 1.15 g/cm³ fills 869.57 cm³, while the same kilo at 1.2 fills only 833.33 cm³. Filled and pigmented products run denser than clear resin, so read the figure off the data sheet. One limit: this tab converts a single material. It does not split a mixed batch by weight, because that split needs both part densities, and guessing them is how off ratio batches happen. Builders will recognise the pattern from the concrete volume calculator: size the space first, then worry about how the material is sold.

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