Updated: a day ago
First, place a container/whiskey glass on a scale and tare the scale (zero it with the container on the scale).
Fill the container with water and measure the number of grams it takes to fill the container to your desired height, i.e. 200g
This will be the approximate weight of wax per container. Wax is only slightly lighter than water (specific gravity of around 0.8-0.98), depending on the blend.
Now plug this weight into the formula below:
(grams of wax per container) X (number of containers) = (grams needed)
(grams needed) ÷ 1000 (grams in 1kg) = (kg of wax needed)
For example, let's say you wanted to make 6 candles in a 230ml glass. The wax weight per container is 200g (as you don’t fill the glass right to the top)
200 x 6 = 1200 grams of wax
1200 ÷ 1000 = 1.2 kg of wax
In this example, you would need at least 1.2kg of wax to fill 6 x 220ml glasses. It is a good idea to round up this number. It's always better to have a little wax left over than to not have enough!
Always remember when the wax cools down, it shrinks. So always have extra wax to top up the candle to the desired height you want.