How long a candle burns depends on several variables, including the type of wax used, the type of wick, the presence of additives and the candle's size. Typically, smaller candles with smaller wicks can be expected to burn at a rate of 7 to 9 hours per ounce of wax.
Larger candles with larger wicks deplete wax more quickly at a rate of approximately 5 to 7 hours per ounce. Due to the multiple factors involved in candle burning, a burn test is often the best method of determining a specific candle's lifespan.
Candles can be made from many different substances, including paraffin, beeswax, gel and even spermaceti, all of which burn at different rates. The size of a candle's flame, which also affects burn time, is largely determined by its wick.