You mix a fresh batch of epoxy, pour it into your mould, and then — nothing left for the last two cavities. Or you mix way too much, watch half of it sit in the cup and go to waste, and feel quietly terrible about it. If this sounds familiar, you are not alone. Almost every beginner resin crafter in India has been through this exact frustration at least once.
The good news is that figuring out how much resin you need for a mould is not complicated math. It is just a couple of simple steps that most tutorials skip over. Once you learn to measure your mould volume before mixing, you will stop wasting material and stop running short mid-pour.
This guide walks you through every method — from the water displacement trick to shape-based formulas — with real examples for common Indian craft projects like coasters, trays, clocks, and Rakhi moulds. We have also included a handy comparison table and batch-size tips so you always mix the right amount.
Quick Answer: How Much Resin Do I Need for a Mould?
If you just need a fast answer before you start:
- Fill your mould with water using a measuring syringe or small measuring cup.
- The volume of water (in ml) = the volume of resin you need.
- Add 10–15% extra to account for mixing cup waste and air bubbles.
- Split that total by your resin's mix ratio (e.g., 1:1 means half Part A, half Part B).
- Mix only that amount — no more, no less.
That is the whole process. The rest of this guide explains each step in detail so you can apply it to any mould, any shape, any size.
Why Getting the Volume Right Actually Matters
Resin is sold in fixed kit sizes — 100g, 200g, 500g, 1kg. Once you open and mix it, the clock starts ticking. Most standard epoxy resins have a pot life of 20–45 minutes, after which the mixture starts to thicken and becomes unusable.
Mixing too little means you have to rush through a second batch mid-project. Mixing too much means leftover resin that cures in the cup and goes straight to the bin. Both situations cost you money.
For multi-cavity moulds — like a set of four coasters or a 12-cavity Rakhi mould — the stakes are even higher. A small error per cavity multiplies across all cavities. Knowing how to measure resin for moulds before you open a single bottle is the single habit that separates crafters who feel in control from those who feel like they are always guessing.
If you have ever had sticky, undercured resin, incorrect volume measurement is sometimes the hidden culprit — too little hardener relative to resin throws off the ratio. Read more about that in Why Your Resin Is Still Sticky After 24 Hours — and How to Fix It Before You Ruin the Piece.
The Water Displacement Method (No Maths Needed)
This is the easiest and most reliable method for any irregular or organic-shaped mould. You do not need to know the shape's formula — just water and a measuring tool.
What You Need
- Your silicone mould
- A 5ml or 10ml syringe, or a small measuring cup with ml markings
- Water
- A piece of paper to note the reading
Steps
- Place your mould on a flat surface.
- Fill it with water up to the exact level you want your resin to reach.
- Pour that water into a measuring cup and note the ml reading.
- Dry the mould completely before pouring resin — any water residue will cause cloudiness or adhesion issues.
- Add 10–15% to the measured volume to cover mixing cup waste.
For example, if your round coaster mould holds 45ml of water, plan to mix 50–52ml of total resin (Part A + Part B combined).
This method works perfectly for flower-shaped, hexagonal, geode, and any other irregular moulds where geometry-based calculation would be unnecessarily complicated.
Calculating Volume by Shape
If you prefer not to use water (especially for moulds that are hard to dry quickly), you can calculate the volume mathematically. Here are the formulas for the most common shapes Indian crafters use.
Round / Circular Mould (Coasters, Clocks)
Volume = π × r² × depth
Where r = radius (half the diameter) and depth = how deep the mould cavity is. Use cm for measurements and the result will be in cm³ (which equals ml).
Example: A 10cm diameter coaster mould with 0.8cm depth → π × 5² × 0.8 = 3.14 × 25 × 0.8 = 62.8ml
Rectangle / Square Mould (Trays, Frames)
Volume = Length × Width × Depth
Example for how to calculate resin for tray mould 9x12: A 9cm × 12cm tray with 1.5cm depth → 9 × 12 × 1.5 = 162ml
Half-Sphere / Dome Mould
Volume = (2/3) × π × r³
Example: A 6cm diameter dome mould (r = 3cm) → (2/3) × 3.14 × 27 = 56.5ml
Oval / Ellipse Mould
Volume = π × a × b × depth (where a and b are the two radii of the ellipse)
| Mould Shape | Formula | Typical Volume (ml) | Suggested Batch Size (with 12% buffer) |
|---|---|---|---|
| Round coaster, 10cm dia, 0.8cm deep | π × r² × d | ~63ml | ~71ml |
| Rectangle tray, 9×12cm, 1.5cm deep | L × W × D | ~162ml | ~182ml |
| 12-inch clock mould, 1cm deep | π × r² × d | ~731ml | ~820ml |
| Small pendant, 3cm dia, 0.4cm deep | π × r² × d | ~2.8ml | ~3.2ml |
| Half-sphere dome, 6cm dia | (2/3) × π × r³ | ~56ml | ~63ml |
Volume Examples for Common Indian Craft Moulds
Resin Quantity for a Round Coaster Set of 4
A standard Indian coaster mould is typically 9–10cm in diameter and about 0.7–1cm deep. Using the formula above, one coaster holds roughly 45–63ml. For a set of 4, that is 180–252ml of mixed resin.
Add your 12% buffer: plan for 200–280ml total batch. If your resin kit is 200g (which is roughly 200ml for most standard epoxy resins with density close to 1g/ml), one kit will just about cover a set of 4 standard coasters.
How Much Resin Needed for a 12-Inch Clock Mould
This is one of the most common questions from Indian crafters. A 12-inch (approximately 30.5cm) clock mould that is 1cm deep needs about 730ml of mixed resin. With a buffer, plan for 820–850ml.
That means you need at least an 800g or 1kg epoxy kit. Do not try to stretch a 500g kit — you will run short and have a half-filled clock face.
For deep-pour clock moulds (2cm or more), the volume roughly doubles. Also note that in Indian summers, pouring 800ml+ in a single batch can cause overheating. Read Deep Pour vs Thin Pour Epoxy in Indian Summers: Why Your Resin Overheats in May and What to Do About It before attempting a large clock pour.
Small Jewellery and Keychain Moulds
Small moulds are tricky because the volume per cavity is tiny — often 1–5ml — but you still need a minimum workable batch of 15–20ml to mix properly. Mixing less than 10ml of epoxy resin is very difficult to get accurate ratios for.
For very small pieces, UV resin is often a better choice since you can use it directly from the bottle without mixing. See UV Resin vs Epoxy Resin for Small Moulds: Which One Actually Works Better for Keychains, Pendants, and Jewelry in Indian Humidity? for a full comparison.
Mixing Ratio and Batch Size: How to Scale Up Correctly
Once you know your total volume needed, you need to split it correctly between Part A (resin) and Part B (hardener) based on your product's mix ratio.
Most Indian epoxy resin kits are either 1:1 by volume or 2:1 by volume. Always check your specific product label — mixing by weight vs. by volume gives different results for some resins.
1:1 Ratio (Equal Parts)
If you need 100ml total: mix 50ml Part A + 50ml Part B.
2:1 Ratio (Two Parts Resin to One Part Hardener)
If you need 90ml total: mix 60ml Part A + 30ml Part B.
A common beginner mistake is measuring 2:1 as 50ml + 25ml and then topping up randomly. Always calculate the total first, then split. For a detailed guide on ratios, check out How to Choose the Right Resin Ratio for Your First Project: 1:1 vs 2:1 Explained for Indian Beginners.
Quick Ratio Reference Table
| Total Volume Needed | 1:1 Ratio (Part A / Part B) | 2:1 Ratio (Part A / Part B) |
|---|---|---|
| 50ml | 25ml / 25ml | 33ml / 17ml |
| 100ml | 50ml / 50ml | 67ml / 33ml |
| 200ml | 100ml / 100ml | 133ml / 67ml |
| 500ml | 250ml / 250ml | 333ml / 167ml |
| 800ml | 400ml / 400ml | 533ml / 267ml |
Practical Tips to Avoid Wasting Resin
Even with perfect calculations, some resin always stays in the mixing cup. Here is how to keep that waste to a minimum.
- Use a flexible silicone mixing cup. You can squeeze out almost every drop. Rigid plastic cups leave a lot stuck to the sides.
- Scrape the cup walls as you pour. Use a silicone spatula and pour slowly.
- Have a small backup mould ready. Keep a simple coaster or small tray mould nearby. Pour leftover resin into it instead of letting it cure in the cup.
- Batch similar projects together. If you are making coasters, make 4–6 at once rather than one at a time. You use your resin more efficiently.
- Do not mix more than your pot life allows you to pour. If your resin has a 30-minute pot life and you are doing detailed work, mix in two smaller batches rather than one large one.
- Weigh, do not eyeball. A digital kitchen scale that reads in 0.1g increments is the most useful tool for consistent batch sizes.
Calculating Resin for Rakhi and Multi-Cavity Moulds
Multi-cavity moulds are where volume calculation really pays off. With a 12 or 13 cavity Rakhi mould, each small cavity might hold just 2–4ml, but across all cavities that adds up to 30–50ml — and you need to know this before mixing.
The water displacement method works beautifully here. Fill all cavities with water using a syringe, then pour that water into a measuring cup. That total is your resin volume. Add 15% buffer for multi-cavity moulds since you lose a bit more to the cup and spatula when pouring into many small spaces.
Shrebhavi carries several popular Rakhi moulds that Indian crafters use every season. The 12in1 Designer Rakhi Mould and the 12in1 Rakhi & Bracelet Mould are both popular for Raksha Bandhan resin gifts. For a full 13-cavity set, the 13 Cavity Rakhi Mould is a great choice, and the 12pcs Rakhi Set Mould lets you make a complete gifting set in one pour session.
For flat, shallow moulds like the Mackup/Colour Mixing Plate Mould, the rectangle formula (L × W × D) usually gives a good estimate, but always verify with the water method since the actual cavity may have curved edges that reduce the real volume.
For inspiration on how to use these moulds creatively, Creating Unique Monsoon Decor: A Step-by-Step Guide to Using Silicone Molds with Resin has some lovely project ideas.
Sample Calculation: 12-Cavity Rakhi Mould
- Each Rakhi cavity: approximately 3ml
- 12 cavities × 3ml = 36ml total cavity volume
- Add 15% buffer: 36 × 1.15 = 41.4ml — round up to 45ml
- For 1:1 ratio resin: mix 22.5ml Part A + 22.5ml Part B
- For 2:1 ratio resin: mix 30ml Part A + 15ml Part B
Safety Notes for Measuring and Mixing
Resin is a chemical product. Measuring and mixing it safely is just as important as getting the volume right.
- Always wear nitrile gloves. Resin can cause skin sensitisation with repeated exposure. Do not use latex gloves — they can react with some resins.
- Work in a ventilated space. Open windows or use a fan blowing outward. Epoxy fumes are mild but unpleasant, and UV resin can be more irritating.
- Do not mix resin near food preparation areas. Use dedicated measuring cups and spatulas that are never used for food.
- Dispose of cured resin waste properly. Let leftover resin cure fully before throwing it in the bin — liquid resin should never go down the drain.
- In Indian summers, work in the cooler part of the day — early morning or after 7pm. High ambient temperatures accelerate curing and reduce your working time significantly.
- Keep children away from uncured resin, hardener, and mixing tools at all times.
Frequently Asked Questions
How do I know how much resin to buy for a new mould I have never used before?
Use the water displacement method before your first pour. Fill the mould with water, measure it in ml, add 15% for waste, and that is your total batch size. Then check what kit size covers that amount. For example, if your mould needs 180ml, a 200g kit will be just enough — but if you are making a set of 4 coasters, buy a 500g kit to be safe and have material left for touch-ups.
Can I mix resin in very small quantities — like 5ml or 10ml?
Technically yes, but it is very difficult to get the ratio accurate at such small volumes using regular measuring cups. A 0.1g precision digital scale helps. For truly tiny amounts (under 10ml total), UV resin is a much better option since it requires no mixing at all — you apply it directly and cure it under a UV lamp.
My resin always seems to run short even when I calculate correctly. What am I missing?
A few common culprits: First, check if your mould has a slightly larger cavity than you measured (silicone can stretch). Second, are you accounting for the resin that stays in the mixing cup and on the spatula? That can be 5–10ml even in a careful pour. Third, if you are using alcohol inks or pigments in large amounts, the added volume from those additives is usually negligible but worth noting for large batches.
Does the density of resin differ from water? Will my water measurement be accurate?
Most standard epoxy resins have a density very close to 1g/ml (usually 1.05–1.15 g/ml), so water measurement is accurate enough for craft purposes. The slight difference is well within the 10–15% buffer you add. For industrial or specialty resins with higher filler content, the density can differ more — but for the resins sold for craft use in India, water displacement is perfectly reliable.
How much resin do I need for a 9×12 inch tray mould?
A 9×12 inch tray is approximately 22.9cm × 30.5cm. At 1.5cm depth, that is 22.9 × 30.5 × 1.5 = roughly 1,048ml. That is over 1 litre of mixed resin — you would need a 1kg kit at minimum, and ideally 1.2kg to have a safe buffer. For a shallower 0.8cm pour, you need about 558ml, so a 600g kit would work. Always measure the actual internal cavity of your tray mould, not the outer dimensions.
Is it better to mix one large batch or multiple smaller batches for a big mould?
For large moulds in Indian summers, multiple smaller batches are often safer. A very large single batch generates more heat as it cures (this is called an exothermic reaction), which can cause yellowing, cracking, or warping in the mould. Pour in layers of 6–8mm at a time, letting each layer reach a gel stage before adding the next. This is especially important for clock moulds and large tray moulds.
Wrapping Up
Knowing how much resin you need for a mould before you start mixing is one of those small habits that makes a huge difference to your craft experience. It saves you money, reduces frustration, and means you spend more time actually creating and less time cleaning up wasted material.
The water displacement method is your best friend for irregular shapes. Shape formulas are reliable for standard round, square, and rectangular moulds. Always add a 10–15% buffer, always split your total by your resin's mix ratio, and always have a small backup mould nearby for leftover resin.
Whether you are making a set of handmade Raksha Bandhan Rakhis, a batch of monsoon-themed coasters, or a large decorative clock, the principle is the same: measure first, mix second, pour with confidence.
Browse Shrebhavi's range of silicone moulds and resin materials at Shrebhavi.in — and if you are still figuring out which resin type suits your project, our blog has guides covering everything from mix ratios to humidity management for Indian crafters.