Weight vs volume: Why a scale is a candle makers best friend

Exact measurements are vital in candle making. But what kind of measurements should you rely on (mass ie: weight / kilos or volume ie litres / mls)?

A candle is comprised of combined ingredients: wax, fragrance, a wick, a vessel / glass, and maybe dye. You need to figure out how much of each ingredient you require for best performance, and then replicate that result in the future.

Any good candle maker must have an accurate instrument of measurement, being a digital scale. Consistency is key!


Let's delve in to the quandry: When testing candles … should you use weight or volume?


  • Weight shows how heavy something is.
  • Volume tells us how much space something takes up.

When it comes to candle making, measuring by weight will always give you the more decisive result. So there's no point wondering how many mls of fragrance you should add. Weigh it!

Water is the basis of the metric system:

1 litre of liquid water weighs 1 kilogram.

1 millilitre of water has a mass of 1 gram.

This relationship is known as 'relative density'. (For water it equals 1.0). 

Candle wax and fragrance oils are lighter than water. This means that one litre of wax or a litre of fragrance oil will always weighless than one kilogram. Candle wax is approximately 10% lighter than water, with a relative density of 0.9 ie: relative to water.

Volume also changes with temperature. The relative density will be different for differing waxes and for different oils. 1 litre of one fragrance oil will have a different weight to 1 litre of another fragrance oil. 1 kg of water can be shipped in 1 litre bottle. However, fragrance oil might need to be shipped in a 1.25 litre bottle in order to compensate for the extra volume. 

Fragrance oils have varied densities. This means some oils are heavier than others. Have you spotted a disclaimer on our site that says something along the lines of, 'we fill by weight, not volume'? This means that fragrance bottles of one type of fragrance may have different fill levels but still weigh exactly the same. So, a bottle of Pina Colada 50ml and a bottle of 1 Million Type would both contain 50 ml  but when you put them side by some, one appears to contain less, and the more. How can that be? Some fragrance oils weigh more than others, and so they take up less or more volume. A fragrance oil that takes up more space is less dense.

Another reason to rely on weight is that fragrance oil capacity, a.k.a 'fragrance load', shows the total fragrance oil that wax can hold. Weight is also used here to specify recommended wax fragrance oil retention on products as specified by manufacturers. One wax might be capable of holding 10% fragrance oil, i.e.: 10% of its own weight. E.g. You have 310g wax and an 8% load capacity. This candle wax can only hold 24.8g of fragrance oil (310 x 8%).

More good reasons to rely on weight in candle making: Wax and fragrance oil are always sold by weight, and not by volume. You would also need to rely upon weight to establish the final weight of your finished product for shipping. We do not record volume on the ingredient label, only weight.



Imagine we were forced to measure by density in candle making rather than weight. That would involve a fully functioning familiarity of volume-based calculations. Ouch!

Let’s say you were some kind of genius and actually preferred to work with volume, not weight, and wished to use a measuring beaker with line markings in mls. First, you’d have to convert your wax from solid to liquid before proceeding. You don’t have that issue with weight. Your product can come in any form!

Sounds complicated? It's actually very simple.

Avoid volume, go for mass. If you're going to make candles, you will need a digital scale. They're affordable and will give you accurate measurements so you get your ratios right.

If you want to delve into this question further, please check out this blog on candle making mathematics. Candle making is fun and accessible for all, so you needn't be bogged down in unnecessary technicality either if you're not so inclined. 




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