Resin Mixing Ratios Explained (Get Perfect Results Every Time)

February 13, 2026 · 9 min read

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Resin Mixing Ratios Explained (Get Perfect Results Every Time)

The mixing ratio is the single most important factor in resin success. Get it wrong and your resin won’t cure. Get it right and you’ll have perfect results every time.

Most beginners struggle with ratios because they don’t understand the difference between weight and volume, or they eyeball measurements instead of using a scale. This guide clears up the confusion.

You’ll learn what mixing ratios mean, how to measure accurately, and why precision matters so much.

What Is a Mixing Ratio?

A mixing ratio tells you how much resin (Part A) to mix with how much hardener (Part B). The two parts must combine in a specific proportion for the chemical reaction to work.

Common ratios you’ll see:

1:1 ratio (equal parts resin and hardener)
2:1 ratio (two parts resin, one part hardener)
3:1 ratio (three parts resin, one part hardener)
4:1 ratio (four parts resin, one part hardener)

The first number is always resin. The second number is always hardener.

Example: 1:1 Ratio

50 grams resin + 50 grams hardener = 100 grams total
2 ounces resin + 2 ounces hardener = 4 ounces total

Example: 2:1 Ratio

100 grams resin + 50 grams hardener = 150 grams total
4 ounces resin + 2 ounces hardener = 6 ounces total

The ratio doesn’t change based on how much you mix. A 1:1 ratio is always equal parts, whether you’re mixing 10 grams or 1000 grams.

By Weight vs By Volume

This is where most confusion happens. Your resin instructions will specify “by weight” or “by volume.” These are NOT the same.

By Weight

Weight measures mass using a scale. This is the most accurate method.

Example (1:1 by weight):

Place cup on scale
Tare to zero
Add resin until scale reads 50g
Tare to zero again
Add hardener until scale reads 50g
Total: 100g mixed resin

Why it’s better: Resin and hardener have different densities. Weight accounts for this automatically.

By Volume

Volume measures liquid amount using measuring cups or syringes. This method is less precise.

Example (1:1 by volume):

Pour resin to the 50ml mark
Pour hardener to the 50ml mark
Mix together

The problem: Even though volumes are equal, the weights might not be. If your resin specifies weight but you measure by volume, your ratio will be off.

Which Method Should You Use?

Always use weight when possible. It’s more accurate and eliminates confusion.

Use a digital scale{rel=“nofollow sponsored”} that measures to 0.1 grams. This precision prevents the small errors that cause curing failures.

If your resin instructions give both weight and volume ratios, use weight. Ignore the volume measurement.

How to Measure by Weight (Step-by-Step)

This method works for any ratio.

What you need:

Digital scale{rel=“nofollow sponsored”} (measures to 0.1g)
Mixing cup
Your resin instructions (to confirm ratio)

For a 1:1 ratio:

Place empty cup on scale
Press “tare” to zero the scale
Pour resin until you reach your target weight (example: 60g)
Press “tare” to zero the scale again
Pour hardener until you reach the same weight (60g)
Mix thoroughly for 3 minutes

For a 2:1 ratio:

Place empty cup on scale
Tare to zero
Pour resin until you reach double your target (example: 80g for resin)
Tare to zero
Pour hardener until you reach your base target (40g for hardener)
Mix thoroughly

Pro tip: Write your target weights on a sticky note before you start. When you’re wearing gloves with wet resin, you don’t want to be doing math.

Common Ratios Explained

1:1 Ratio (Most Beginner-Friendly)

Equal parts resin and hardener.

Examples:

50g + 50g = 100g total
100g + 100g = 200g total
1 oz + 1 oz = 2 oz total

Pros:

Easiest to measure
Hardest to mess up
Most craft resins use this ratio

Cons:

None, really

Common brands with 1:1:

Craft Resin{rel=“nofollow sponsored”}
ArtResin
Most Amazon craft resins

2:1 Ratio

Two parts resin, one part hardener.

Examples:

100g resin + 50g hardener = 150g total
200g resin + 100g hardener = 300g total
4 oz resin + 2 oz hardener = 6 oz total

Pros:

Common in professional resins
Often formulated for thicker pours

Cons:

Easier to make measurement errors
Requires more careful measuring

Common brands with 2:1:

Many table-top and bar-top epoxies
Some marine epoxies

3:1 and 4:1 Ratios

Less common in craft resin. More common in industrial or specialty applications.

Example (3:1):

150g resin + 50g hardener = 200g total

Example (4:1):

200g resin + 50g hardener = 250g total

These ratios require extra precision. Small errors in hardener amount cause big problems.

Why Precision Matters

Epoxy resin needs a specific chemical ratio to cure. The molecules must match up exactly.

If you add too much resin:

Excess resin molecules have no hardener to react with
Surface stays sticky or tacky
May never fully cure

If you add too much hardener:

Excess hardener molecules have no resin to react with
Can cause excessive heat during curing
May yellow or crack
Can also stay sticky (surprising but true)

How precise do you need to be?

Within 2-3%: Usually cures fine
Off by 5-10%: Partial cure, sticky spots
Off by 15%+: Won’t cure at all

This is why eyeballing doesn’t work. A “roughly equal” pour might be off by 20%.

Calculating How Much Resin You Need

Before you mix, figure out how much total resin your project requires.

For Molds

Most molds list their capacity in ml or ounces. Convert this to grams for weight measuring.

Quick conversion:

1 ml of mixed resin ≈ 1.1 grams
1 fluid ounce ≈ 30 ml ≈ 33 grams

Example:

Mold capacity: 60ml
Need approximately 66 grams total mixed resin
For 1:1 ratio: 33g resin + 33g hardener

For Flat Pours (Coasters, Trays)

Formula: Length × Width × Depth × 1.1 = grams needed

Example (4-inch square coaster at 1/4 inch deep):

4 inches × 4 inches × 0.25 inches = 4 cubic inches
4 × 16.4 (conversion factor) = 65.6 grams total

Round up and add 10% for safety. Mix 75 grams total.

Pro tip: Mix more than you think you need. Running short mid-pour is worse than having leftover resin.

Common Measuring Mistakes

Mistake 1: Using Measuring Cups

Measuring cups aren’t precise enough for resin. The graduations are too far apart. You might be off by 5-10% and not know it.

Fix: Use a digital scale. Always.

Mistake 2: Not Taring Between Parts

If you add resin and hardener without taring, you’re measuring total weight, not individual parts.

Wrong way:

Add resin (scale reads 50g)
Add hardener (scale reads 100g)
This is actually 50g resin + 50g hardener ✓

But for 2:1, this fails:

Add resin (scale reads 100g)
Add hardener (scale reads 150g)
This is 100g resin + 50g hardener ✓
But only if you tared!

Fix: Tare after adding each part. The scale should return to zero before adding the next part.

Mistake 3: Mixing Different Brands

Don’t mix resin from one brand with hardener from another. The formulations won’t match.

Fix: Always use resin and hardener from the same kit.

Mistake 4: Using Old Resin with Fresh Hardener

Resin degrades over time. Old resin won’t cure properly even with fresh hardener.

Fix: Use resin within 6-12 months of opening. Mark bottles with the date you opened them.

Mistake 5: Confusing Weight and Volume

Your instructions say “2:1 by weight” but you measure by volume using cups.

Fix: Read your instructions carefully. Check whether it specifies weight or volume. Use the correct method.

What If You Don’t Have a Scale?

If you absolutely can’t use a scale, use graduated mixing cups{rel=“nofollow sponsored”}. But accept that your precision is lower.

Tips for measuring by volume without a scale:

Use cups with clear, accurate markings
Read at eye level (not from above)
Measure on a flat surface
Pour slowly and carefully
Accept that you’ll have more failures

Better solution: Buy a digital kitchen scale. They cost $15-25 and eliminate 80% of beginner problems.

Troubleshooting Ratio Problems

My resin is sticky after 24 hours. You likely got the ratio wrong. See our sticky resin fix guide for solutions.

My resin got really hot and cracked. Too much hardener caused an exothermic spike. Remake with precise measurements.

My resin is still liquid after 48 hours. Way off on ratio, or you poured from the wrong bottle. See resin not curing guide.

I mixed my resin but forgot what ratio it was. You can’t fix this. You don’t know if it’s correct. Start over with a fresh batch and precise measurements.

Tips for Consistent Results

Write down your recipe. Note the exact weights you used for each project. When you get perfect results, you can repeat them exactly.

Example notes:

Project: Coasters
Ratio: 1:1 by weight
Resin: 60g
Hardener: 60g
Total: 120g
Result: Perfect cure

Use the same scale every time. Different scales can read slightly differently. Stick with one.

Calibrate your scale monthly. Use a known weight (like a nickel, which weighs 5g) to check accuracy.

Mix in batches. For multiple items, mix one large batch rather than several small ones. This reduces accumulated measurement errors.

Advanced: Adjusting Ratios (Don’t Do This)

Some people ask: “Can I change the ratio to make resin cure faster or harder?”

No. Don’t do this.

The ratio is chemistry, not a recipe. You can’t adjust it like adding extra sugar to tea. The resin manufacturer spent months testing to find the exact ratio that works.

Changing the ratio will:

Prevent proper curing
Create weak or brittle resin
Cause yellowing or cracking
Waste your materials

The only time to adjust: Never. Always follow the manufacturer’s specifications exactly.

Next Steps: Master Your Mixing

Now you understand resin ratios. Here’s what to do:

For your next project:

Check your resin’s specified ratio (on the bottle or instruction sheet)
Confirm whether it’s by weight or volume
Use a digital scale for weight measurements
Tare between adding resin and hardener
Write down your measurements

If you’re having curing problems:

Review our complete troubleshooting guide
Fix sticky resin caused by wrong ratios
Learn when resin won’t cure at all

Prevent ratio mistakes:

Buy a quality digital scale (it pays for itself in saved resin)
Read instructions carefully before every mix
Use the tare function religiously
Mix slowly and deliberately

The mixing ratio is non-negotiable. Get this one thing right and most other resin problems disappear. Invest in a good scale. Follow your kit’s specifications exactly. Measure carefully every time. That’s the secret to perfect resin results.