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How to Work Out Wax and Fragrance Per Batch
Manesh Jayawardhana
CIO & Co-founder
Twelve vessels, one pour, and you need to know how much wax to melt and how much fragrance oil to add. Get the first wrong and you’re re-melting; get the second wrong and the oil separates out on top.
Both are straightforward arithmetic with one measurement people skip.
Measure the vessel with water
Stated capacity and usable volume are different numbers, especially in tapered or thick-based vessels.
Fill one with water to the level you’d actually pour to, then weigh or measure it. That’s your working volume — and it’s often meaningfully less than the number on the supplier’s listing.
wax weight = volume × fill level × wax density
Soy wax is around 0.9 g/ml. A 240 ml vessel filled to 85%: 240 × 0.85 × 0.9 ≈ 184 g. Twelve vessels need about 2.2 kg, plus a little extra for what stays in the pouring jug.
Fill level between 80% and 90% leaves headroom without looking underfilled. Right to the brim looks generous and spills when the wax liquefies.
Fragrance is a percentage of the wax
Not of the total, and not of the vessel volume. Of the wax weight.
At 8% fragrance load with 2.2 kg of wax: 2,200 × 0.08 = 176 g of fragrance oil, added to the wax rather than replacing part of it.
Every wax has a maximum load stated on its datasheet, commonly somewhere around 8-12% for soy. Exceeding it is the cause of several familiar problems: oil pooling on the surface, a greasy feel, poor burn, sooting, and in extreme cases the candle simply not setting properly.
More fragrance does not mean more scent throw past that point — it means oil the wax can’t hold.
Temperature matters when adding it. Fragrance oil should go in within the range the wax manufacturer specifies, usually around 60-80°C depending on the wax, and be stirred thoroughly for a couple of minutes. Added too hot and volatile components flash off; too cool and it doesn’t bind properly.
| Input | Basis | Typical |
|---|---|---|
| Wax weight | Volume × fill × density | 0.9 g/ml for soy |
| Fill level | Vessel volume | 80-90% |
| Fragrance | % of wax weight | Check the datasheet |
| Add temperature | Wax specification | Around 60-80°C |
Wick sizing needs a test burn
The part no calculation settles.
Vessel diameter is the starting point, and every wick manufacturer publishes a chart mapping diameter to wick size. But the correct wick also depends on the wax, the fragrance load, any colourant, and the vessel material and thickness — all of which affect how the wax melts.
Two failure modes:
Too small produces tunnelling — a narrow melt pool that burns down the middle leaving a wall of wax. Once a candle tunnels on its first burn it tends to keep doing it.
Too large produces excessive flame, sooting, and a melt pool hot enough to be a safety concern.
The test: burn a single candle for the recommended first burn — long enough for the melt pool to reach the vessel edge, typically three to four hours — and observe. Then adjust and test again.
That’s why sensible makers test a wick before pouring a batch of thirty.
Common mistakes to avoid
- Using the supplier’s stated vessel capacity instead of measuring.
- Calculating fragrance as a percentage of the finished candle rather than of the wax.
- Exceeding the wax’s stated maximum load.
- Adding fragrance outside the specified temperature range.
- Pouring a full batch before test-burning a single candle.
How to do it with Candle Wax Calculator
The Candle Wax Calculator sizes the batch from vessel volume.
- Measure vessel volume with water rather than trusting the listing.
- Set the fill level — 80-90% leaves sensible headroom.
- Set fragrance as a percentage of wax weight, within the datasheet maximum.
- Test-burn one candle before pouring the rest.
Other craft calculators are in the tools directory.
Frequently asked questions
Why measure vessels with water?
Because stated capacity and usable volume differ, particularly in tapered or thick-based vessels. Water gives you the volume that actually holds wax.
How much fragrance can wax hold?
It depends on the wax — many soy waxes are rated to around 8-10%, and exceeding the rating causes the oil to separate, pool on top, or affect the burn. Follow the datasheet.
How do I choose a wick?
Diameter is the starting point, but wax type, fragrance load and colourant all affect the burn. Test burns are unavoidable — tunnelling or sooting is only visible after several hours.
Final thought
Measure the vessel, read the datasheet, and burn one before pouring thirty. The arithmetic is easy; the wick is the part that decides whether the batch is any good.