Epoxy Resin Calculator
Estimate exactly how much epoxy you need for a rectangular pour. Enter dimensions in inches, add waste, and get gallons, liters, ounces, and kit count instantly.
How to Use This Epoxy Calculator
This epoxy calculator is designed for makers, DIYers, woodworkers, and installers who need accurate resin estimates before ordering materials. If you are coating a tabletop, pouring a river table, sealing artwork, or creating a bar top finish, this tool helps you avoid buying too little—or way too much—epoxy.
Just enter the length, width, and intended thickness of your pour in inches. The calculator determines raw volume, adds a waste factor, and then converts the total into useful purchasing units like gallons, quarts, liters, and fluid ounces.
What the Calculator Gives You
- Total epoxy required in gallons after waste is included
- Equivalent volume in liters, quarts, and fluid ounces
- Number of kits needed based on your chosen kit size
- Part A and Part B amounts based on your resin mix ratio
- Project footprint in square inches and square feet
Formula Used
Step 1: Find project volume in cubic inches
Volume = Length × Width × Thickness
For example: 48 × 24 × 0.125 = 144 cubic inches.
Step 2: Convert cubic inches to gallons
There are 231 cubic inches in 1 US gallon.
Gallons = Cubic Inches ÷ 231
Step 3: Add waste allowance
A waste factor accounts for cup residue, roller loss, edge runoff, and small overpours.
Total Gallons = Base Gallons × (1 + Waste% ÷ 100)
Choosing the Right Thickness
Thickness is usually the biggest variable in epoxy projects. Typical ranges:
- Seal coat: very thin, often 1/64" to 1/32"
- Flood coat: around 1/16" to 1/8"
- Deep pour: 1/4" to 2"+ per layer (product-specific)
Always check your manufacturer specs. Some epoxies are made for thin coats only, while deep-pour formulas are engineered for thicker castings with lower heat buildup.
How Much Extra Should You Add?
A common waste allowance is 5% to 15%. If your surface is large, uneven, or has routed channels, 15% to 20% may be safer.
- Use 5% for small, flat, controlled pours.
- Use 10% as a practical default for most projects.
- Use 15%+ for textured edges, absorbent wood, and beginner margin.
Mix Ratio Planning (Part A : Part B)
Different systems use different resin-to-hardener ratios, most commonly 1:1 or 2:1 by volume. The calculator splits your total requirement into Part A and Part B automatically so you can pre-plan containers and mixing batches.
If your product uses ratio by weight rather than volume, use your product's technical data sheet and a digital scale for final batching.
Pro Tips for Better Epoxy Results
1) Pre-condition materials
Keep resin and hardener in a stable room-temperature environment before mixing. Cold epoxy is thicker, traps more bubbles, and mixes less evenly.
2) Mix thoroughly, then transfer and remix
Under-mixed epoxy is one of the top causes of tacky spots. Scrape sides and bottom, then transfer to a second cup and mix again.
3) Stay within pour depth limits
Exceeding maximum pour depth can cause overheating, yellowing, cracking, or smoke. Deep pours should be done in controlled layers unless your formula specifically permits single thick pours.
4) Seal porous substrates first
Wood, concrete, and some art substrates can release bubbles. A thin seal coat before the main pour dramatically improves clarity.
Common Mistakes to Avoid
- Guessing volume without measuring thickness carefully
- Ignoring waste and ending up short mid-pour
- Using the wrong ratio or mixing by eye
- Pouring too thick for the epoxy type
- Working outside the recommended temperature range
Quick FAQ
Can I use this for river tables?
Yes. Measure the average length, width, and depth of your epoxy channel. If the shape is irregular, break it into sections and add results.
Can I use this for floor coating?
You can, but floor systems are often estimated by coverage rate (sq ft per gallon) instead of thickness. Always compare with product coverage specs.
What if I am between kit counts?
Round up. Running out during a pour is more expensive than slight overage.
Final Thought
Accurate estimating is the foundation of every successful epoxy job. Use the calculator, plan your batch sequence, and follow your product data sheet for mixing, temperature, and cure windows. A few minutes of planning can save hours of rework—and a lot of resin.