Candle Burn Time Calculator
Burn hours from your own measured rate — and why a candle four times the mass burns for exactly the same time.
This assumes a full melt pool and a wick sized to the diameter, which is the case a well-behaved candle is aiming for. A wick too small tunnels and never reaches the walls, which breaks the relationship entirely — the pool stops following the jar. Nothing is uploaded.
The diameter cancels out completely
A candle's mass goes with the melt-pool area times the height. Its consumption goes with the melt-pool area — a wider pool feeds a bigger flame and burns faster in proportion. Divide one by the other and the area cancels entirely: burn time is height times density over the areal rate, with no diameter in it at all.
| Candle, all 8 cm tall | Wax | Burns at | Lasts |
|---|---|---|---|
| 5 cm across | 141 g | 3.6 g/hr | 39.8 hours |
| 7.5 cm across | 318 g | 8.0 g/hr | 39.8 hours |
| 10 cm across | 565 g | 14.2 g/hr | 39.8 hours |
| 12 cm across | 814 g | 20.5 g/hr | 39.8 hours |
Those candles hold 141 g to 814 g of wax — 5.8 times the mass across the range — and every one of them burns for 39.8 hours. Which is not what the market implies. A larger jar is sold as more candle, and it is more wax; it is not more hours. If you want a candle that lasts, the dimension to buy is the tall one.
Height is what moves it, exactly in proportion
Doubling the height doubles the time, precisely — there is no curve in it. Which also means the last quarter of a candle is a quarter of its life, and a jar that cannot be burned down to the bottom loses exactly that share of what you paid for.
| Height of wax | Burns for | Against 8 cm |
|---|---|---|
| 4 cm | 19.9 hours | 0.50× |
| 6 cm | 29.8 hours | 0.75× |
| 8 cm | 39.8 hours | 1.00× |
| 12 cm | 59.6 hours | 1.50× |
| 16 cm | 79.5 hours | 2.00× |
The areal rate is worth measuring rather than looking up. Grams per hour per square centimetre of pool folds the wax, the wick and the room into one figure — burn a candle you own for a few hours, weigh it before and after, and the number that comes out is yours. A published rate cannot know your wick, and the wick is most of what it is measuring.
How to use
- Weigh a candle you own before and after a burn to get grams per hour.
- Enter that rate and the diameter it came from.
- Enter the candle you are asking about.
- Read the hours, and try changing the diameter.
Frequently asked questions
Does a bigger candle burn for longer?
No — a wider one does not. Mass goes with the melt-pool area times the height, and consumption goes with the melt-pool area, so the area cancels. Three candles 8 cm tall and 5, 7.5 and 10 cm wide hold 141 g, 318 g and 565 g of wax and every one burns for 39.8 hours.
So what does change the burn time?
The height of the wax, exactly in proportion. Double the height and you double the time. That is the whole relationship: height times density over the areal burn rate, with no diameter in it at all.
Then why are big jars sold as lasting longer?
Because they contain more wax, which is true, and people read that as more hours, which is not. If you want a candle that lasts, the dimension to buy is the tall one — a tall narrow candle outlasts a wide shallow one holding far more wax.
How do I measure my own burn rate?
Weigh the candle, burn it for a few hours in normal conditions, weigh it again. Grams lost over hours burned, divided by the melt-pool area, gives an areal rate that folds the wax, the wick and the room into one figure. A published rate cannot know your wick, and the wick is most of what it is measuring.
When does this stop being true?
When the melt pool stops matching the jar. A wick too small tunnels — it burns a narrow shaft and never reaches the walls — so the pool no longer follows the diameter and the cancellation breaks. The relationship assumes a wick sized to the candle, which is what a well-behaved candle is aiming for anyway.
Does the last bit of a candle count?
Proportionally, yes. Since time follows height exactly, the last quarter of the wax is a quarter of the life — and a jar that cannot be burned to the bottom loses exactly that share of what you paid for.
What about multiple wicks?
A multi-wick candle is closer to several small pools than one large one, and this models a single full pool. The direction still holds — more pool area means faster consumption — but calibrate from a candle of the same wick count if you want the number to be right.
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.