One question I occasionally get is, “How do I estimate how long my candle will last?” Here’s how!
It is important to note that wax consumption will depend on the fragrance oil that is mixed in with the wax and also the wick’s capacity and number of wicks. This means that if you change fragrance, fragrance percentage, wax, or wick, you will need to re-test and recalculate your burn rate again. It’s easiest to do this during wick testing.
Step One: Gathering Data
During the wick testing phase, you’ll be testing for the ideal melt pool, hot throw, and vessel sturdiness. One more thing you can do while testing is record start and end candle weights.
- Weigh the candle: wick, wax, vessel, fragrance oils, decorations, and all. If your candle vessel has a lid, exclude it, don’t weigh it.
- When you start your test, record the starting weight and the time you light the candle.
- At the end of your test, blow out the candle. Weigh the candle again and record the ending weight and ending time.
Step Two: Calculations (with Example!)
The starting weight less the ending weight will give you the weight of the wax consumed during the burn. For example, I recently tested a candle that started the test at 498g and ended at 487g.
498g – 487g = 11g
We also need to figure out how long the candle burned. For example, the candle was lit at 10:15am and it was blown out at 12:10pm.
12:10pm – 10:15am = 1 hour and 55 minutes burn time
Now, take the weight of the wax consumed during the burn and divide it by the number of hours burned. (You can use minutes if you like.) This will give you a wax burn rate.
11g / 115 minutes = 0.096g/minute
To convert this to hours:
0.096g/minute x 60 minutes = 5.76g/hour
Step Three: Find Your Candle’s Burn Time
When you finally pour your candles, you should know how much wax is in each one. For the candle in our example, I decided that they would be 12.5oz each (not including vessel or wicks, but including wax and FO.) Since my burn rate is in grams, I’ll convert ounces to grams (it’s more accurate that way). Google makes it easy. 12.5oz is 354g.
Now I divide the weight of the wax (and fragrance oil) by my burn rate.
354g / 5.76 g/hr = 61.45 hours
Woot! We figured out that a 12.5 oz candle will probably burn for just under 61.5 hours. Since candles may burn faster or slower depending on where they are located (for example near a draft or in a still room) I like to couch the burn estimate in range, so I would then put the estimated burn time as 55 – 65 hours.