Candle Wax Calculator: Jar Volume, Wax Weight, Top-Up and the 0.86 Rule

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Opens on the book's Market Batch. Change any number to your own and press Calculate.

Start from fills the boxes below

Jar inside diameter mm

Fill depth mm, to the fill line

Inside height mm, optional: for the brimful check

Or water to the fill line g, for a jar that is not straight-sided

Hot wax density g/mL (soy, about 70 °C)

Set wax density g/mL

The sellers' rule

The run

Fragrance load % of the wax

Jars

Spare %

Enter the jar and press Calculate.

The formula

Volume = π × (diameter ÷ 2)² × fill depth (mm³ ÷ 1000 = mL), or the water to the fill line in grams
Hot wax to the line = volume × 0.887 g/mL; it shrinks about 1 − 0.887 ÷ 0.92 = 3.6 % as it sets, so keep that back for the top-up
The 0.86 rule, water-weight version: water to the line (g) × 0.86. Fluid-ounce version: fl oz × 0.86 = oz of wax (a lower figure: a fl oz of water weighs 1.043 oz)
Wax per jar = fill ÷ (1 + load); the run = that × jars × (1 + spare)

The book's worked example, Chapter 8. The Market Batch jar is 70 mm across inside, poured to 72 mm: π × 35² × 72 = 277.09 mL, × 0.887 = 245.78 g of hot wax (the water-weight 0.86 rule says 238.3 g). At an 8 % load that is 227.6 g of wax and 18.2 g of fragrance a jar; twelve jars plus 5 % = 2,867.4 g of wax.

Never measure from the brim or the container's name: an "8 oz" tin holds 5 oz of wax to its line. Check the wax is plant-based and palm-free in writing; some "coconut" blends contain paraffin. Prices are illustrative US supplier prices from October 2026, shown without a currency sign; put in your own. Everything stays in your browser: no sign-up, nothing stored.