Candle Wax Weight Calculator
How much wax a jar actually takes by weight, and why an 8 oz jar holds under seven ounces of it.
Wax densities cluster near 0.9 g/mL for both soy and paraffin, but they vary — melt a known weight into a measuring jug once and you will have your own figure. Fragrance oil goes in on top of this. Nothing is uploaded.
The label is a volume and the wax is a weight
A jar's size is quoted in fluid ounces, which measure volume. Wax is bought and weighed in ounces of mass. The two share a name and are not the same unit — and the gap runs in one direction, because wax is lighter than water. An 8 oz jar filled to 90% takes 6.76 ounces of wax.
| Jar | Wax at 90% fill | In ounces | Short of the label by |
|---|---|---|---|
| 4 fl oz | 96 g | 3.38 oz | 15.5% |
| 8 fl oz | 192 g | 6.76 oz | 15.5% |
| 12 fl oz | 287 g | 10.14 oz | 15.5% |
| 16 fl oz | 383 g | 13.52 oz | 15.5% |
The shortfall is 15.5% at every size, because it is two fixed factors multiplied — the density of the wax and the share of the jar you actually fill. Even filling to the brim does not reach the label, and even a wax as dense as water would still fall short at a 90% fill. There is no jar size at which the two numbers meet.
Which is where the ordering goes wrong
Wax for 100 eight-ounce candles is 42 pounds, not
the 50 that multiplying the label suggests — a difference of
8 pounds, or nearly a whole case. The arithmetic
that produces the wrong figure looks entirely reasonable on the way past, which is exactly why
it survives: 8 ounces times a hundred is 800 ounces is 50 pounds, and every step of that is
correct except the first.
Erring high is the cheaper direction to err in, so this is not a disaster — but it is a
standing 15% of working capital sitting in a box, and it compounds if the same figure is used
to price the candles.
How to use
- Enter the jar size in fluid ounces.
- Set the fill level you actually pour to.
- Adjust the wax density if you know yours.
- Read the wax per candle and for the whole batch.
Frequently asked questions
How much wax does an 8 oz jar hold?
About 6.76 ounces by weight at a 90% fill. The jar size is quoted in FLUID ounces, which measure volume, while wax is weighed — and wax is lighter than water, so the label always overstates the wax that goes in.
Why is the shortfall the same at every size?
Because it is two fixed factors multiplied: the density of the wax and the share of the jar you fill. At 0.9 g/mL and a 90% fill it comes to 15.5%, and that holds for a 4 oz jar and a 32 oz one alike.
Would filling to the brim fix it?
No. A full 8 oz jar still takes only about 7.5 ounces of wax, because the density gap remains. Even a wax as dense as water would fall short at a 90% fill. There is no jar size at which the two numbers meet.
How much wax should I order for a batch?
For a hundred 8 oz candles, about 42 pounds — not the 50 that multiplying the label gives. The arithmetic that produces the wrong figure looks entirely reasonable: 8 ounces times a hundred is 800 ounces is 50 pounds, and every step is right except the first.
Is over-ordering actually a problem?
Erring high is the cheaper direction, so it is not a disaster. It is a standing 15% of working capital sitting in a box, and it becomes a real problem if the same wrong figure is used to price the candles.
What density should I use?
0.9 g/mL is a fair working figure for both soy and paraffin, and they vary. Melt a known weight into a measuring jug once and you will have your own number, which is worth doing if you make in quantity.
Does the fragrance count towards the fill?
Yes — it goes into the same jar. Fragrance load is a percentage of the wax weight rather than of the jar, which means adding it to a jar-full of wax overflows. That is a separate calculation and worth doing before you pour.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.