How much fragrance oil for candles?

The short version: at 8% you need 36 g (1.28 oz) of fragrance oil per pound of wax, or 80 g per kilo. Most soy container blends are happiest somewhere between 6 and 10%, and going higher rarely gives you the stronger candle you were hoping for.

That is the easy part. The part that causes real problems is that “8%” means two different things depending on who wrote it down, and the two are not interchangeable.

Fragrance oil per pound and per kilo

Every figure here is a percentage of the wax weight, which is the convention almost every supplier and spec sheet uses.

You will also see the old rule of thumb: one ounce of fragrance oil per pound of wax. That is 6.25%, so it is a perfectly reasonable starting point and slightly lighter than most people assume. It is a starting point, not a target.

Percent of wax versus percent of total

This is the single most expensive misunderstanding in candle making, because it does not announce itself. Both readings produce a number. Only one of them is the number your supplier meant.

• Percent of wax weight. The industry norm. 8% means 8 g of oil for every 100 g of wax. The finished candle weighs 108 g.
• Percent of total weight. Used by some suppliers and plenty of older guides. 8% means the oil is 8% of the finished candle, and the oil is part of the weight it is being measured against.

Starting from a fixed amount of wax, the second reading needs more oil than the first, not less. That trips people up, so here it is worked through with a kilo of wax:

percent of wax: oil = wax × load ÷ 100
percent of total: oil = wax × load ÷ (100 − load)

At normal loads the gap is a few grams per kilo, which sounds harmless. It is not, if you are already running near the top of what your wax will hold — that few grams is exactly what pushes a batch from “fine” to a layer of oil sitting on top of every jar.

What each wax will actually hold

Fragrance capacity is a property of the wax, not a preference. Ask a wax to carry more oil than its structure can bind and the excess has nowhere to go.

These are typical industry figures. Your manufacturer’s spec sheet beats every one of them — formulations differ between brands and even between batches, and the sheet is free to read.

What going over the limit looks like

• Sweating. Beads of oil on the surface, usually within a day or two of pouring. The wax has released what it could not hold.
• Seeping. Oil pooling at the bottom or around the edges, often only visible once the candle has set fully.
• A soft, greasy top. The surface never firms up properly and marks with a fingerprint.
• Poor burn behaviour. Excess oil at the wick changes how the flame behaves. This is the reason it matters beyond looks.

The awkward truth is that none of this makes the candle smell stronger. Oil that the wax cannot bind does not evaporate into the room in any useful way — it sits there. Past a wax’s limit you are paying for fragrance oil to ruin your own candles.

Why more oil is not more scent

Scent throw is not a function of load alone. It depends on the wax, the specific fragrance, the wick and the size of the room, and every one of those can matter more than the last two percent of oil. A fragrance that is weak at 8% is usually a fragrance that is weak, or a wick that is not making a big enough melt pool, and pushing to 12% almost never rescues either.

The productive order is: get the wick right first, so you have a full melt pool. Then adjust load. Changing both at once tells you nothing about which one helped.

Weigh it, do not measure it

Fragrance oils vary in density, so a millilitre of one is not the same mass as a millilitre of another. Every load percentage in this guide, and on every supplier spec sheet, is a percentage by weight. Use a scale that reads to 0.1 g and zero it with the pot on.

Add the oil at the temperature your wax supplier specifies, stir for a full two minutes, and give it time. Under-stirring produces the same symptoms as over-loading and gets misdiagnosed constantly.