The arithmetic
Divide the price by the burn time. A $38 candle rated for 85 hours costs about 45 cents an hour. An $11.58 candle rated for 35 hours costs about 33 cents. The cheap one is genuinely cheaper to run, but by nothing like the gap the shelf price implies.
Run it the other way and the result is often uncomfortable. A $70 designer candle rated for 60 hours costs about $1.17 an hour, which is roughly three times the discount-store candle. Whether that is worth it is your call, but at least it is now a call rather than a guess.
Why ounces mislead
Weight is the number most retailers lead with, and it is the least reliable of the three. Two 12 ounce candles can differ by twenty hours of burn depending on wax type, wick size, and how many wicks the vessel carries. A three-wick candle consumes wax substantially faster than a single wick of the same weight.
Wax matters too. Coconut and soy blends generally burn slower and cooler than paraffin, which is part of why they turn up in more expensive candles. It also means a lighter soy candle can outlast a heavier paraffin one.
Where the published numbers come from
Almost every burn time you see is supplied by the maker, and makers measure under conditions that flatter the product. There is no industry standard requiring a particular session length, room temperature, or trim discipline, so two honest brands can publish very different numbers for physically similar candles.
This is exactly why we run the Burn Lab, and why every page on this site says whether a figure was measured by us or stated by the maker. When we have not measured it, we say so rather than quietly borrowing someone else's number.
How to use it when you shop
Work out cost per hour before you compare anything else. It collapses price, size, and burn time into one figure, and it survives discounting: a candle on sale genuinely improves on this measure, whereas a bigger jar often does not.
Then apply judgement the number cannot capture. Throw, vessel quality, and whether you actually enjoy the scent are worth real money. The point is not to buy the cheapest hour available. It is to know what an hour costs before you decide.