Measure your jar, choose the wax and fragrance load, and see the wax and oil for each candle, what to buy for the batch and what each candle costs.
Safety tips from the US National Fire Protection Association's candle safety tip sheet.
A container holds a set volume. Multiply it by the density of solid wax and you have the weight of wax and oil that fills it: an 8 fl oz (237 ml) jar of soy wax at 0.90 g/ml takes about 213 g. That blend is then split by your fragrance load. At 8% of the wax weight, wax is 213 ÷ 1.08 = 197 g and fragrance oil the other 16 g. Times eight candles, plus your extra, gives the amounts to buy.
The calculator uses the density of solid wax because that is what fills the jar in the end. Melted wax takes up more room and shrinks as it sets, which is why some candles need a top-up pour.
The water test works for any shape: fill the empty container with water to where the wax will stop, then pour the water into a measuring jug or weigh it. One gram of water is one millilitre, close enough for candles. For straight-sided jars you can measure instead: the volume of a round jar is π × (inside diameter ÷ 2)² × fill height, and of a box, length × width × fill height.
Each wax choice fills in a density and a fragrance ceiling from a maker's published sheet. They are starting points: your own wax's data sheet always wins, so type its figures over ours.
To find the real density of your own wax, weigh a finished test candle, take away the weight of the empty jar, and divide by the weight of water the jar holds to the same line.
Each one shows its working and names its sources.
Trays, coasters and moulds in layers: resin and hardener by volume or weight at your product's own ratio.
Plaster and water by weight for any mould, from USG's published mixing ratios, with set times.
How long to cut each cord and how much to buy, from a rule of thumb you can adjust.
Balloons by size and colour for any length of garland, with a printable shopping list.
A project card with materials from any calculator, steps and drying timers, saved in your browser.
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Try WebTraceCheckBoth are in use, and data sheets rarely say which, so the calculator lets you choose. As a share of the wax, 8% means 8 g of oil for every 100 g of wax. As a share of the whole blend, it means 8 g in every 100 g of wax and oil together, which is slightly more oil. One ounce of oil per pound of wax is 6.25% of the wax weight.
Because you rarely fill a jar to the brim. Filling it with water to your own fill line measures the space the wax will really take, whatever the jar's shape. Weighing the water is the easiest way: 1 g of water is 1 ml.
Densities vary between waxes, blends and batches, and wax shrinks as it sets, so a jar may take a top-up. Weigh one finished test candle, subtract the empty jar, and divide by the water it holds: that is your own wax's density, ready to type into the calculator.
This site does not suggest wick sizes. The right wick depends on the wax, fragrance, dye and container together, so test-burn a candle and follow your wick supplier's chart.
Stay at or below the maximum on your own wax's data sheet. The calculator flags a load above the ceiling you set. Check each fragrance oil's safety data sheet from its supplier too, including its flash point.