Free Two-Component Epoxy Mix Ratio calculator
Split any volume of two-part epoxy into exact Part A and Part B amounts — enter your total volume and ratio (1:1, 2:1, 4:1 or custom) to see the millilitres for each component and percentage breakdown, updated live, as you type.
On this page11 sections
Volumes are by volume. Always confirm the mix ratio on your product's data sheet — weight-ratio products require a scale, not a measuring cup.
Results are estimates. Consult a professional.
How the epoxy mix ratio calculator works
Two-component (2K) epoxy is a thermoset adhesive sold as two separate parts: Part A (the resin) and Part B (the hardener or curing agent). Neither part cures alone; the chemical cross-linking reaction only starts when the two are combined in the correct proportion. The mix ratio specifies that proportion — either by volume or by weight, depending on the product.
This calculator works with volumetric mix ratios, which is how most consumer and trade epoxy products are specified. You enter the total volume you need to mix and the ratio (e.g. 2:1), and the calculator tells you exactly how much to measure out from each container.
Mix by volume vs. mix by weight
The most important thing to check on any epoxy data sheet is whether the mix ratio is by volume or by weight (mass). They are not the same. Part A resin and Part B hardener typically have different densities — the resin is often denser than the hardener — so a 2:1 ratio by volume produces a different proportion than a 2:1 ratio by weight.
By volume — use measuring cups or graduated pumps
Most consumer epoxy products (bar tops, table pours, art resin) specify their ratio by volume. Measuring by volume is intuitive and easy with graduated mixing cups or matched pumps. A pump that delivers equal strokes of each part is calibrated for a 1:1 volume ratio; two strokes of A to one stroke of B matches a 2:1 volume ratio.
By weight — use a scale
Marine, structural, and laminating epoxies (West System, System Three) typically specify ratios by weight because the proportions are more precise and temperature-stable when measured on a scale. A 5:1 system by weight often looks like a 4:1 or even 3:1 system by volume — following volume marks on a mixing cup will produce an under-cured result.
Common epoxy mix ratios and when they're used
Epoxy manufacturers choose mix ratios based on the chemistry of their resin and hardener systems. A given ratio cannot be changed arbitrarily — using too much or too little hardener leaves the cured epoxy tacky, brittle, or with reduced chemical resistance. The most common ratios are 1:1, 2:1, 3:1, 4:1, and 5:1.
| Ratio (A:B) | Typical application | Part A % of total | Note |
|---|---|---|---|
| 1:1 (vol) | Art / deep-pour / self-levelling | 50% | Equal parts; easiest to measure |
| 2:1 (vol) | General purpose; bar tops; floor coats | 66.7% | Most common trade ratio |
| 3:1 (vol) | Some casting and laminating resins | 75% | Less common |
| 4:1 (vol) | Specialty casting; UV-cure aids | 80% | High resin fraction |
| 5:1 (wt) | West System marine; structural bonding | 83.3% | Typically by weight, not volume |
Ratios by volume unless noted. "Typical application" reflects common product positioning — always verify with your specific product's data sheet.
Pot life, working time, and cure time
Once you mix Part A and Part B, the exothermic curing reaction begins immediately. Pot life (also called working time) is how long the mix stays fluid and workable. Cure time is how long until the piece reaches its rated hardness. Both depend heavily on temperature, the ratio, and the total volume in the mixing cup.
The exothermic reaction accelerates itself: heat speeds up the cure, which produces more heat, which speeds it up further. A large volume in a tall, narrow cup generates more heat and a shorter pot life than the same volume spread thinly across a flat surface. Professional casters pour into wide, shallow trays and work in cool rooms for this reason.
- Mix only what you can use in the pot life listed on your data sheet (typically 20–45 minutes for room-temperature pours).
- Work in thin layers for deep pours: stacked layers of 1/4–1/2 inch reduce heat build-up versus a single 2-inch pour.
- Cool temperatures extend pot life — mixing in a cool garage in January gives more working time than the same product in a summer workshop.
- Never try to slow a cure by adding less hardener — off-ratio epoxy cures incompletely, producing a tacky or soft result.
Epoxy applications by ratio type
Countertop and floor coatings (typically 2:1)
Epoxy floor and countertop coatings are usually 2:1 by volume. The large volumes involved (often 1–10 gallons per coat) make accurate measuring critical. Graduated pour containers and matched pumps reduce waste; under-mixing or off-ratio batches leave soft spots or pinholes.
Deep casting and river tables (typically 1:1)
Deep-pour or slow-cure resins for river tables and casting molds are often 1:1 and formulated with long pot lives (hours, not minutes) to allow air bubbles to escape. They generate less heat per unit of cured volume, making the equal-parts ratio easier to manage.
Marine and structural bonding (typically 5:1 by weight)
Structural marine epoxies (West System 105/205, 105/206, 105/207) are specified by weight ratio — typically 5:1. The resin is much denser than the amine hardener, so the weight-ratio method ensures the correct stoichiometry. Marine users always weigh; the large resin fraction (83%) makes a volume estimate significantly off.
A worked example: mixing 300 mL at 2:1
James is coating a wood bar top with a 2:1 volume-ratio epoxy. He calculates he needs 300 mL of mixed epoxy for a single coat. He has a graduated mixing cup and two separate containers of Part A and Part B.
Step 1 — Total denominator
ratioA + ratioB = 2 + 1 = 3 parts total.
Step 2 — Measure Part A
partA = 300 × (2 ÷ 3) = 200 mL. James pours 200 mL of resin into the mixing cup.
Step 3 — Measure Part B
partB = 300 − 200 = 100 mL. He adds 100 mL of hardener to the same cup. The cup now holds 300 mL total.
Step 4 — Mix thoroughly
James stirs for at least 3 minutes, scraping the sides and bottom, then transfers to a second clean cup and stirs for another minute. This double-cup technique removes any unmixed pockets clinging to the first cup's walls.
Epoxy mixing terms
Frequently asked questions about the free Two-Component Epoxy Mix Ratio calculator
About this Two-Component Epoxy Mix Ratio calculator
This epoxy mix ratio calculator runs entirely in your browser — no data is sent anywhere, and Part A and Part B volumes update the moment you change the total or ratio. It works for any volumetric ratio: 1:1, 2:1, 3:1, 4:1, 5:1 or custom.
It is part of our home & garden calculators. Browse the full calculator library for more home improvement tools.