How Much Wax Do I Need to Fill a Candle Jar?

Wax is lighter than water, so a jar that holds 10 oz of water holds less than 10 oz of wax. The quick method is to weigh the water the jar holds at your fill line and multiply by the wax's specific gravity. NorthWood says 0.85 is the average for candle wax, and Glass Now says to use 0.86 if you do not know your wax. The result is an estimate, so confirm it by weighing a real filled jar.

How do I work it out, step by step?

1. Set the fill line. NorthWood fills to about 1/4 inch (6 mm) below the rim. Lone Star says to fill no higher than the jar's widest point. Pick one and stay with it.
2. Weigh the water. Put the empty jar on the scale and tare it. Pour in water to the fill line and read the weight. Grams are easier than ounces here.
3. Multiply by the wax factor. Use your wax's specific gravity if its sheet lists one. NorthWood lists 0.84 for its soy flakes and 0.90 for beeswax, and calls 0.85 the average. This is the wax and oil together.
4. Take out the fragrance oil. The oil sits inside the same space as the wax, so it uses part of the fill. The worked example below takes it as a percent of the wax weight.
5. Add extra for a second pour. NorthWood notes that waxes that shrink as they cool may need one.
6. Check it with a real jar. Pour a test candle, weigh the empty jar and the filled jar, and subtract. Use that number from then on.

Worked example

Say the water in your jar weighs 9.5 oz (269 g) at the fill line, your wax's factor is 0.85 and your fragrance load is 8 percent of the wax weight. All numbers are examples.

• Space available, wax and oil together: 9.5 x 0.85 = 8.075 oz (229 g)
• Wax = fill / (1 + load) = 8.075 / 1.08 = 7.48 oz (212 g)
• Oil = wax x load = 7.48 x 0.08 = 0.60 oz (17 g)
• Check: 7.48 + 0.60 = 8.08 oz, which matches 8.075 apart from rounding.

For a batch of 12 jars: wax = 12 x 8.075 / 1.08 = 89.72 oz (5.6 lb, or 2.5 kg) and oil = 89.72 x 0.08 = 7.18 oz (203 g). Check: 89.72 + 7.18 = 96.90 oz, and 12 x 8.075 = 96.90.

Some recipes take the load from the total instead. See Is fragrance load a percent of the wax or the total?

No jar in hand yet? Estimate from size

This works for straight-sided jars only. Fill volume = 3.1416 x (inside width / 2)^2 x fill height. Then volume in cm3 x 0.85 = grams of wax and oil together. It is an estimate, so weigh a real jar before you scale.

Made-up example: inside width 7.5 cm, fill height 8 cm.

• Volume = 3.1416 x 3.75^2 x 8 = 353.4 cm3
• Wax and oil = 353.4 x 0.85 = 300.4 g (10.6 oz)
• At 8 percent of the wax weight: wax = 300.4 / 1.08 = 278.1 g, oil = 278.1 x 0.08 = 22.3 g. Check: 278.1 + 22.3 = 300.4 g.

Measure the inside width, not the outside, and the height of the fill line, not the jar.

How far can the wax factor move the answer?

The factor you pick changes the result. This table takes example water weights at the fill line and multiplies by 0.77, 0.85 and 0.90, the low end, the average and the top of NorthWood's list. Each result is wax and oil together.

What if I know the jar's size in fluid ounces?

Glass Now multiplies the container's fluid ounces by 0.86, but a printed volume may be the brim, not your fill line. Why fluid ounces mislead: see Weigh or measure candle ingredients?

Can I just weigh a filled jar?

Yes. Glass Now calls this the most precise way: weigh the empty jar, fill it with wax, weigh it again, and subtract. Do it once per jar type, and write the number on your recipe.

Common mistakes

• Using the jar's printed volume as the wax weight. Wax weighs less than water.
• Filling to the brim. You need room for wick centering and, with some waxes, a second pour.
• Forgetting that fragrance oil takes up part of the space.
• Mixing up fluid ounces and weight ounces.
• Using the same factor for every wax. Check the sheet.
• Never weighing a real finished candle to check.

Questions

Is 0.85 right for soy, coconut and paraffin?

It is an average. NorthWood lists 0.84 for its soy flakes and says to use 0.85 for waxes it does not list. Glass Now uses 0.86. NorthWood's own waxes run from 0.77 to 0.90, which is why I say to weigh a real jar. On a jar with 10 oz of water, the gap between 0.77 and 0.90 is 1.3 oz of wax.

How much extra wax should I melt?

Enough for the second pour and what stays in the pitcher. I do not have a source with a standard percentage. Weigh the pitcher before and after pouring a batch and use your own number.

Do I need to count the wick and the sticker?

They take almost no space. Weighing a real filled jar catches them anyway.