Candles
Candle wax calculator
How much wax a batch actually needs, once you've accounted for headspace and the weight your fragrance oil displaces.
How this is calculated
Three steps: work out the volume you're actually filling, convert that volume to a pour weight using the density of your wax, then split that weight between wax and fragrance oil.
The third line is where most calculators go wrong. Fragrance oil is part of what goes into the jar, so it occupies some of the space. If you calculate wax to fill the vessel and then add fragrance on top, you overflow - by roughly the fragrance percentage. Dividing rather than multiplying keeps the finished candle at the fill line.
Wax densities used here
Grams per millilitre, measured at pour temperature rather than room temperature:
- Soy - 464, 444, C-3 - 0.90
- Coconut-soy blend - 0.88
- Paraffin - 0.90
- Beeswax - 0.96
- Palm - 0.92
- Gel - 0.86
You may have met the older shortcut: fill a jar with water, weigh it, multiply by 0.86. That works because water is 1 g/ml by definition, so the multiplier is only wax density expressed as a ratio. It's a good field method when a vessel's stated volume isn't printed anywhere.
Worked example
Twelve 8 fl oz jars in soy wax at an 8% fragrance load, poured to 90%:
- Fill volume
- 8 × 29.57 × 0.90 = 212.9 ml per jar
- Pour weight
- 212.9 × 0.90 = 191.6 g per jar
- Wax
- 191.6 ÷ 1.08 = 177.4 g per jar
- Fragrance
- 191.6 − 177.4 = 14.2 g per jar
- Batch of 12
- 2,129 g wax - 4.69 lb - and 170 g fragrance oil
Order about 5% more wax than the figure above. Between residue left in the pitcher, the top-up pour on soy, and the occasional jar you re-melt, a batch calculated to the gram will leave you short.
Fragrance load: share of wax, or share of total?
Both conventions are in use and suppliers aren't consistent about which they mean. The difference is small at low loads and meaningful at high ones.
Share of wax weight is the more common convention among US suppliers and the one most fragrance manufacturers use when publishing a maximum. An 8% load means 8 g of oil for every 100 g of wax, giving 108 g of finished candle.
Share of total weight means 8 g of oil in every 100 g of finished candle, so 92 g of wax. Same stated number, slightly less fragrance.
The gap is about half a percentage point at 8% and grows from there. It matters most at the top of a wax's stated capacity, where the difference between 10% and 11.1% is the difference between a clean candle and one that sweats oil.
Common questions
How much wax do I need for an 8 oz candle jar?
Around 177 g of soy wax - about 6.3 oz by weight - for a jar filled to 90% at an 8% fragrance load. The figure comes out lower than the jar's stated size because "8 oz" describes fluid volume, while wax is sold and weighed by mass, and soy is lighter than water.
Why doesn't an 8 oz jar take 8 oz of wax?
Fluid ounces measure volume and ounces measure weight; the two only coincide for water. Soy wax is about 10% less dense, so a jar holding 8 fl oz of water holds roughly 7.2 oz of soy by weight - less again once you leave headspace.
How much extra wax should I buy?
About 5% over the calculated figure covers pitcher residue and top-up pours. If you're testing a new fragrance or vessel, budget more - first batches rarely go cleanly.
Does fragrance load change how much wax I need?
Yes. Fragrance oil occupies volume in the jar, so a higher load means proportionally less wax for the same vessel. At a 10% load you use roughly 9% less wax than an unscented candle in the same jar.
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