Resin Ratio Calculator

Quick ratio reference: common batch sizes

Use these tables when you need a fast answer without entering numbers. All figures are rounded to one decimal place. For any amount not listed, use the calculator above.

1:1 ratio — Part A and Part B amounts

2:1 ratio — Part A and Part B amounts

💡 Grams shown use a density of 1.05 g/ml for Part A. Part B density varies by brand — always use a scale for exact weights rather than converting from ml.

Epoxy resin mixing ratios by brand

The ratio is always printed on the product label, but this reference covers the most common craft and art epoxy brands. Note that some brands produce multiple formulas — the table shows the most common product from each brand. If you have a deep pour or specialty formula, check that specific label.

⚠️ Weight ratios differ from volume ratios for most 2:1 brands because Part A and Part B have different densities. For all 2:1 brands, use the weight-based ratio from your product's technical data sheet when measuring by scale. For 1:1 brands, weight and volume ratios are typically the same.

How to mix epoxy resin correctly: step-by-step

Getting the ratio right is only part of a successful mix. Technique matters equally — incorrect mixing causes the same failures as incorrect ratios. Follow these steps every time regardless of brand or ratio.

Step 1: Calculate your amounts

Use the calculator above to get exact Part A and Part B amounts for your target total. Add 10% buffer to account for resin that sticks to mixing cups and stir sticks. Never guess — even experienced crafters use calculators because the cost of a ruined batch always exceeds the cost of 30 seconds with a calculator.

Step 2: Measure by weight on a digital scale

Place your mixing cup on a digital scale and press tare to zero. Pour Part A to the target weight. Press tare again to zero. Pour Part B to the target weight. This two-tare method eliminates cup weight and ensures both parts are measured against zero, not against each other's weight — the most common volume measurement mistake.

If using volume measuring cups instead of a scale, use graduated mixing cups and read measurements at eye level at the bottom of the meniscus. Volume measuring is significantly less accurate for ratios that are not 1:1.

Step 3: Mix slowly and thoroughly

Stir slowly for 3–5 minutes, scraping the sides and bottom of the cup with a silicone spatula. Fast stirring introduces air bubbles — slow and deliberate is better. The mixture is fully blended when it looks completely clear with no streaks, wisps, or cloudiness visible when you hold the cup to light. Undermixing is the most common cause of soft spots in cured resin — those unmixed zones never cure properly.

Step 4: Pour within working time

Pour as soon as mixing is complete. Most epoxy resins have a working time (pot life) of 20–45 minutes at 70–75°F before the mixture begins to gel in the cup. Hot weather shortens this significantly — at 85°F, working time can drop to 10–15 minutes. See the resin temperature guide for working time at different temperatures.

Why getting the ratio right matters — and what goes wrong

The chemistry behind the ratio

Epoxy resin cures through a chemical reaction between the resin (Part A, which contains the epoxide groups) and the hardener (Part B, which contains the amine or anhydride curing agent). The ratio is a stoichiometric requirement — the manufacturer has calculated exactly how many molecules of hardener are needed to react with each molecule of resin. Too little hardener means unreacted resin molecules remain. Too much hardener means excess amine molecules remain on the surface.

This is why you cannot "adjust" the ratio to change cure speed or hardness — the chemistry does not allow it. Temperature changes cure speed safely; ratio changes cause failure.

Too much Part A (not enough hardener)

The most common ratio error, usually from imprecise volume measuring. Symptoms: resin stays permanently sticky or tacky after the expected cure time. Surface may feel firm but remains soft underneath. The unreacted resin cannot be saved — the batch must be discarded. Prevention: measure by weight, not volume.

Wrong ratio is the #1 cause of sticky or uncured resin. If your batch hasn't cured properly, use the Sticky Resin & Cure Time Guide to diagnose whether it can be saved.

Too much Part B (too much hardener)

Less common but equally damaging. Symptoms: cloudy or white surface film (amine blush), resin may cure hard but with a hazy finish. In severe cases, resin may cure brittle and crack. Mild amine blush can sometimes be sanded off and recoated, but the underlying cure quality is compromised.

How far off is too far off?

Most quality epoxy resins have some tolerance — typically ±5% from the stated ratio before visible problems occur. Beyond that, results become unpredictable. Volume measuring with cups is typically ±10–15% accurate, which is why it causes problems even when done carefully. A 0.1g digital scale is typically accurate to ±0.5%, which is well within safe tolerance for any resin formula.

Volume ratio vs weight ratio: what's the difference?

This is one of the most commonly misunderstood aspects of epoxy mixing, and it matters most for 2:1 ratio resins.

When a product label says "2:1 by volume," it means 2 cups of Part A to 1 cup of Part B. But Part A and Part B have different densities — Part A (resin) is typically 1.1–1.2 g/ml, while Part B (hardener) is typically 0.95–1.05 g/ml. This means the same volume of Part B weighs less than the same volume of Part A.

For a true 2:1 by volume mix, the weight ratio ends up being closer to 100:44 to 100:50 by weight depending on the specific formula. If you measure a 2:1 brand by weight using a 2:1 weight ratio, you are actually adding slightly more hardener by volume than intended. For most craft applications this is within acceptable tolerance. For professional or critical applications, always find the weight-based ratio on your product's technical data sheet.

For 1:1 ratio resins, the volume and weight ratios are typically the same (or very close) because manufacturers formulate them to match — making 1:1 brands more forgiving for both volume and weight measuring.