Introduction
Epoxy is one of the most useful materials in construction, but getting the right amount can be tricky. Mix too little and you won't have enough to finish the job. Mix too much and you waste money on material that hardens before you can use it. This epoxy calculator takes the guesswork out of your project by telling you exactly how much resin and hardener you need.
Simply enter your project type — whether it's a surface coating for a countertop, a flood coat for a river table, laminating, filling, or a seal coat — along with your surface area and desired thickness. The calculator handles all common mix ratios like 1:1, 2:1, 3:1, and 4:1, and it even lets you set a custom ratio if your product requires one. You can add multiple project sections with different shapes, switch between imperial and metric units, and adjust the waste factor to account for spillage and mixing loss. For bar tops and countertops, there's also a seal coat plus flood coat combination mode that calculates both layers at once. The results show your total mixed volume, the exact amount of resin and hardener to measure out, and suggested product sizes to purchase.
How to Use Our Epoxy Calculator
Enter your project details and surface dimensions below, and this calculator will tell you exactly how much epoxy resin and hardener you need to buy for your job.
Project Type — Pick the kind of epoxy work you are doing. Choose from Surface Coating (for countertops and bar tops), Flood/Pour Coat (for thick decorative pours and river tables), Laminating (for fiberglass layups), Filling/Bonding (for gap and crack repair), or Seal Coat (for a thin bubble-preventing base layer).
Unit System — Select Imperial (inches, fluid ounces) or Metric (millimeters, milliliters) depending on how you prefer to measure.
Mix Ratio (Resin : Hardener) — Choose the mix ratio that matches your epoxy product. Common options are 1:1, 2:1, 3:1, and 4:1. If your product uses a different ratio, select Custom and type in your own numbers.
Seal Coat + Flood Coat Combination — If your project type is Surface Coating or Flood/Pour Coat, you can turn on this toggle to plan a thin seal coat followed by a thicker flood coat. This splits the results so you know how much epoxy each phase needs.
Thickness — Enter how thick you want each layer of epoxy to be. The unit changes based on your project type and unit system. For surface coats, a typical range is 1/16 to 1/4 inch. For flood coats, 1/4 to 2 inches is common. For laminating and seal coats, thickness is measured in mils or millimeters.
Number of Coats — Enter how many coats you plan to apply. Each coat adds the same thickness, so total material multiplies accordingly. If you enabled the combo mode, you will set coat counts separately for the seal coat and flood coat.
Waste Factor — Enter a percentage for extra material to cover spillage, mixing loss, and uneven surfaces. A value between 5% and 15% is typical for most epoxy projects.
Project Sections — Define the surfaces you need to coat. Each section lets you pick a shape — Rectangle, Circle, Triangle, or Custom Area — and enter its dimensions. Click "Add Section" to include more surfaces like additional countertops or tabletop pieces. The calculator adds all sections together to find your total project area. If you need help determining the area of an irregularly shaped surface, our square footage calculator can assist with that step.
Once everything is filled in, the calculator instantly shows your total mixed volume, the exact amount of resin needed, and the exact amount of hardener needed. It also suggests product sizes to purchase, displays a per-section breakdown table, and generates a bar chart comparing each section's area and epoxy volume.
What Is Epoxy and How Do You Calculate How Much You Need?
Epoxy is a two-part material made of resin and hardener. When you mix these two parts together, a chemical reaction starts that turns the liquid into a hard, clear, and durable surface. Epoxy is widely used in construction and DIY projects for coating countertops, bar tops, tabletops, floors, and even for filling cracks or bonding materials together.
Why Accurate Epoxy Measurement Matters
Getting the right amount of epoxy is one of the most important steps in any project. If you mix too little, you won't have enough to cover your surface evenly, which can leave thin spots or bare areas. If you mix too much, you waste money on extra material that hardens and cannot be reused. Since epoxy must be mixed at a specific mix ratio — such as 1:1 or 2:1 (resin to hardener) — measuring both parts correctly is critical. An incorrect ratio can cause the epoxy to cure too slowly, stay sticky, or never fully harden at all.
Key Factors That Affect How Much Epoxy You Need
- Surface Area: The length and width (or diameter for round surfaces) of the area you plan to coat directly determines the volume of epoxy required.
- Thickness: A thin surface coat at 1/16 of an inch uses far less material than a thick flood coat poured at 1/4 inch or deeper. River table pours can be 1 to 2 inches thick and require significantly more epoxy.
- Number of Coats: Many projects need more than one coat. A common approach is to apply a thin seal coat first (about 8–15 mils thick) to soak into the surface and prevent air bubbles, followed by a thicker flood coat for the final finish.
- Mix Ratio: Different epoxy brands use different ratios. A 1:1 ratio means equal parts resin and hardener. A 2:1 ratio means twice as much resin as hardener. Always follow the manufacturer's instructions.
- Waste Factor: It is smart to add 5% to 15% extra material to account for mixing losses, spillage, drips off edges, and material left in mixing cups. A 10% waste factor is standard for most projects.
Common Epoxy Project Types
Surface coatings are the most popular use. These are thin layers applied to countertops and tabletops, usually between 1/16 and 1/4 inch thick. Flood coats or pour coats are thicker applications used for decorative finishes and river tables, typically ranging from 1/4 inch up to 2 inches. Laminating epoxy is used to wet out fiberglass cloth or fabric at about 10–20 mils per layer. Seal coats are very thin coats brushed on before a flood coat to fill pores in wood and stop bubbles from forming. Filling and bonding applications use epoxy to fill gaps, repair cracks, or glue materials together, where the amount depends on the size of the void.
Epoxy is just one of many materials you might need to estimate for a construction or renovation project. If you're also working on flooring, check out our flooring calculator or tile calculator. For projects involving concrete, grout, or mortar, we have dedicated calculators for those materials as well. If your epoxy project involves building a countertop surface on top of a new structure, our board foot calculator can help you estimate the lumber you'll need.
Tips for Working with Epoxy
Always mix epoxy thoroughly for at least two to three minutes, scraping the sides and bottom of your container. Work in a room that is between 70°F and 85°F (21°C–29°C) for the best curing results. Use a torch or heat gun to pop surface bubbles within the first 20 minutes after pouring. For porous surfaces like wood, a seal coat is strongly recommended before applying a thicker finish coat. Finally, measure by volume, not by weight, unless the product label says otherwise — resin and hardener often have different densities, so equal weights are not the same as equal volumes.
If you're finishing a larger surface project that also involves painting surrounding walls or trim, our paint calculator can help you estimate how much paint to buy. And for projects where epoxy is being applied over new drywall or patched surfaces, the drywall calculator can help you plan those materials in advance.