How much wax your container candles need

How to work out candle wax

Candle wax comes from the volume to fill: the area of the jar's base times the wax depth, which is the inside height minus the space left at the top. With the inside diameter in inches, the area is 3.1416 × radius × radius; cubic inches divided by 1.805 give fluid ounces. If you only know the brimful capacity printed on the jar, the calculator takes the top space off as if the walls were straight.

The volume then becomes weight through the density of the solid wax, from the makers' data sheets:

• soy 920 kg/m³, that is 0.92 times the weight of water (Cargill, NatureWax C-3);
• paraffin 900 kg/m³ (Wikipedia);
• beeswax 960 kg/m³ (Candles and Supplies safety data sheet);
• rapeseed 900 kg/m³ (candle.gr safety data sheet).

The calculator uses the solid density, not the melted one: wax shrinks as it cools and the candle gets a second pour to fill the sinkhole (From Nature With Love), so the right weight is the one that fills the jar once the wax is cold.

Fragrance load is a percentage of the wax weight, not of the total: 10% of 300 g of wax is 30 g of fragrance, and the candle weighs 330 g (NI Candle Supplies). CandleScience writes the same 10% as 1.6 oz per pound of wax. Wax and fragrance together have to fit in the jar, so the calculator divides the volume by the space each ounce of wax takes with its fragrance. The starting loads come from the data sheets: 10% for soy and paraffin in containers (CandleScience), 6% for beeswax (CandleScience), up to 10% for rapeseed (Kerax). Fragrance oil counts as 1 g per ml; data sheets give specific gravities from 0.96 to 1.11 (Voyageur), and you can change it in the advanced options.

One wick per jar up to 4 inches across: Northwood's example is a 4 inch soy candle with one LX 24 or two LX 10. Wider jars get two or more wicks, each one sized for the diameter divided by the number of wicks (Northwood).

Worked example: four jars and a wide tumbler

These are the US values the calculator opens with: four jars 3 inches across and 4 inches tall, one tumbler 4 1/2 inches across and 4 inches tall, soy wax with 10% fragrance oil, 1/2 inch left at the top.

• 3 inch jar: wax 3 1/2 inches deep, 13.7 fl oz to fill, 12.0 oz of wax and 1.2 oz of fragrance oil
• 4 1/2 inch tumbler: wax 3 1/2 inches deep, 30.8 fl oz, 27.1 oz of wax (1.69 lb) and 2.7 oz of fragrance oil
• Total: 4 × 12.0 + 27.1 = 75.3 oz, that is 4.71 lb of wax, and 7.5 oz of fragrance oil by weight, 7.2 fl oz
• Wicks: one for each 3 inch jar, two for the tumbler because it is wider than 4 inches: 6 wicks, at least 4 + 1 = 5 inches long

To buy: one 5 lb bag of soy wax, two 4 fl oz bottles of fragrance oil and 6 pre-tabbed wicks.

In the UK the calculator opens in centimetres: four jars Ø 8 × 9 cm and a Ø 11 × 10 cm jar with 1 cm left at the top. Each 8 cm jar holds 402 ml, 339 g of soy wax and 34 g of fragrance; the 11 cm jar 855 ml, 721 g and 72 g. In total 2.08 kg of wax and 208 g of fragrance: three 1 kg bags, three 100 ml bottles and 6 wicks at least 13 cm long. With the 0.86 rule of thumb (Glassnow) the 8 cm jar would take 402 × 0.86 = 346 g of wax and fragrance; the solid density gives 373 g, 8% more, which is the wax for the repour.

Wax and fragrance oil per jar

Figures from the calculator with soy wax, 10% fragrance load and 1/2 inch left at the top. Sizes are inside diameter × inside height.

Jar	To fill	Soy wax	Fragrance
2 1/2 × 3 in	6.8 fl oz	6.0 oz	0.6 oz
3 × 4 in	13.7 fl oz	12.0 oz	1.2 oz
3 1/2 × 4 in	18.7 fl oz	16.4 oz	1.6 oz
4 × 4 1/2 in	27.9 fl oz	24.5 oz	2.4 oz
4 1/2 × 4 in	30.8 fl oz	27.1 oz	2.7 oz

The 4 1/2 inch jar is the only one in the table that needs two wicks. The same 3 × 4 inch jar with the other waxes, each at its starting load: paraffin 11.8 oz and 1.2 oz of fragrance, beeswax 13.0 oz and 0.8 oz (at 6%), rapeseed 11.8 oz and 1.2 oz. Beeswax weighs more for the same volume because it is denser.

Bags, bottles and wicks to buy

Wax is sold by weight, as flakes or pellets: CandleScience sells soy wax in 1 lb and 10 lb bags, and the calculator starts from a 5 lb bag that you can change to the one you find; in the UK packs of 500 g, 1 kg or 5 kg. The calculator rounds up whole bags only, and the leftover wax goes into the repour or a test candle. Fragrance oil comes in small bottles (the calculator starts from 4 fl oz, 100 ml in the UK): the receipt gives the ounces to weigh and the fluid ounces to buy.

Container wicks come pre-tabbed and cut to length: they should be about 1 inch longer than the jar (From Nature With Love) and get trimmed after pouring. With several jar sizes, the calculator sizes the wicks for the tallest jar.

The space at the top is about 1/2 inch in the From Nature With Love guide and 1 cm in the Supplies for Candles guide.

Common mistakes

• Measuring outside the glass. Thick walls and bases take volume away: measure the diameter and the height inside.
• Working out fragrance on the total. The 10% applies to the wax weight: 300 g of wax takes 30 g of fragrance and the candle weighs 330 g, not 33 g in 330 g (NI Candle Supplies).
• Measuring fragrance in fluid ounces. Fragrance oils do not all weigh the same per fluid ounce: weigh them on a scale and use fluid ounces only to pick the bottles.
• Going past the wax data sheet. With too much fragrance the wick struggles and the flame stays small or goes out (NI Candle Supplies): the soy, paraffin and rapeseed data sheets give 10%.
• One wick in a wide jar. Past 3.5 inches it is already hard to get a full melt pool with a single wick (Northwood): past 4 inches use two smaller wicks.