How Much Wax Do I Need for My Candle Jars?

Why “12 oz” does not mean 12 oz of wax

Most candle jars were made for something else, such as food. The name on the box often comes from the product the jar was first built for, not from candles. One supplier points out that a jar can be named for the weight of honey it holds. Honey is much heavier than candle wax, so the name overstates what wax will fit.

Three different numbers get mixed up, and only one of them is your batch amount:

Suppliers who list a “wax weight to fill line” call it an estimate, because fill lines and wax densities vary a little. Treat it as a good place to start, then test.

The water method, step by step

Water is a handy measuring tool because one ounce of water weighs one ounce. Wax is lighter than water, so the same space holds less wax by weight. The water method turns a space you can see into a weight you can pour.

1. Set the empty, dry jar on a kitchen scale and zero it.
2. Fill it with water to the line where you want the finished wax to reach. Leave room below the rim; many makers keep the wax a little below the top so the flame and lid have space.
3. Write down the water weight.
4. Multiply by your wax’s factor (see the next section). The result is the combined weight of wax and fragrance oil for that jar.
5. Subtract the oil (see the fragrance section below) to get the wax weight.
6. Pour one test candle and weigh it, empty jar first and cooled filled jar after. The difference is the real fill. Adjust if it is off.

Which factor should you use?

The factor is the wax’s density compared with water (its specific gravity). It is not the same for every wax, and it is not a single magic number.

Published data shows the spread. A data sheet for one soy container wax lists a specific gravity of 0.920 to 0.925. The U.S. government’s NIOSH pocket guide lists paraffin wax at 0.88 to 0.92. One wax maker’s guide to this exact method gives different factors for different waxes, from 0.77 to 0.90, and calls 0.85 a rough average. Many makers also quote 0.86 for soy. That figure is a popular rule of thumb among makers. It is not a density that every wax shares, and part of why it runs lower than the data sheet is that it leaves a little headroom.

To measure your own factor, fill the jar with water to your line and weigh it. Empty it, dry it, and fill it with melted wax to the same line. Let it cool and weigh it. Divide the wax weight by the water weight. A hot pour reads a little low because wax shrinks as it cools, so cooled is truer.

You can also let the Fill Weight Calculator do the multiplying. It labels each wax type an average estimate, and it lets you enter your own published or measured density.

Where the fragrance oil fits

Fragrance oil takes up room in the jar. If you pour wax to the line and then add oil, the jar overflows. So the water method gives you the combined wax-and-oil weight, and you split it.

CandleEasy measures fragrance load as a percent of the wax weight. So if your target load is written as a decimal (6% is 0.06), the wax is the combined weight divided by 1 plus that decimal. The oil is what is left.

Example with made-up numbers: your jar holds 10 oz of combined wax and oil, and you plan a 6% load. Wax is 10 ÷ 1.06, about 9.43 oz. Oil is about 0.57 oz. These are sample numbers, not a recommendation. Your wax’s data sheet sets the limit on fragrance load. See how much fragrance oil to use.

Another way to say it: some guides subtract the oil from the wax total. Both ways give the same jar weight, as long as you are clear whether the percent is of the wax or of the total. Pick one and keep it for every recipe.

Scale up to a batch

Multiply each ingredient by the number of jars. With the sample numbers above, six jars need about 56.6 oz of wax and 3.4 oz of oil.

• Plan for a little wax to be left in the pouring pitcher. Weigh what you actually lose over a few batches and add that amount, not a guess.
• Some waxes shrink as they cool. Many makers keep a little melted wax back to top off the surface. Your wax maker’s instructions will say if yours needs it.
• Keep wax and oil in a recorded recipe, along with the jar model and fill line. If you change the wax or the line, test again.
• A wick and a vessel are chosen for a specific fill. A bigger or smaller fill may need a different wick. See how to choose a candle wick.

Common mistakes

• Using the jar’s name as the wax weight.
• Adding the oil on top of a full fill.
• Using volume in fluid ounces as if it were weight in ounces.
• Taking one factor for all waxes, including beeswax and gel, which sit at quite different densities.
• Skipping the test pour before filling a whole batch.