How much fragrance oil for a 100 ml reed diffuser?

About 21 ml at a 25 percent load, assuming the bottle fills to 85 percent. The remaining 64 ml is base.

Reed Diffuser Calculator - Base and Fragrance Oil Split

Q: What is the ratio of fragrance oil to base in a reed diffuser?

Between 20 and 30 percent fragrance oil to 70 to 80 percent base, with 25 percent a usual starting point. Much higher than a candle because a diffuser relies on evaporation rather than heat.

Q: Why is my reed diffuser cloudy?

The fragrance oil has not fully dissolved in the base. Most common with vanilla-heavy and resinous fragrances in plain DPG. A ready-made base with a solubiliser usually fixes it.

How this is calculated

Diffusers are worked by volume rather than weight, since oil and base are both liquid at room temperature and volume is what has to fit the bottle.

fill volume = bottle size × fill level fragrance = fill volume × load base = fill volume − fragrance

Unlike candles, the load here is a share of the total liquid rather than of the base. A 25% diffuser is a quarter fragrance oil and three quarters base.

Worked example

Ten 100 ml bottles at 85% fill and a 25% load:

Fill volume: 100 × 0.85 = 85 ml per bottle
Fragrance: 85 × 0.25 = 21.3 ml per bottle
Base: 85 − 21.3 = 63.8 ml per bottle
Batch of 10: 638 ml base and 213 ml fragrance oil

Choosing a base

DPG is the standard: cheap, and slow to travel up the reeds, which makes for a long-lasting diffuser with a quieter throw. It doesn't dissolve every fragrance well.

Ready-made diffuser bases are usually DPG blended with a solubiliser and a faster carrier. They cost more and handle difficult fragrances better.

Perfumer's alcohol throws fast and strong, and empties fast to match. Better suited to room sprays than reed diffusers.

Not every candle fragrance oil works in a diffuser. Oils high in vanillin or heavy resins can refuse to dissolve in DPG, leaving a cloudy blend that clogs the reeds. Check a fragrance is rated for diffuser use before committing a batch to it.

Common questions

What is the ratio of fragrance oil to base in a reed diffuser?

Between 20% and 30% fragrance oil to 70-80% base, with 25% the usual starting point. Substantially higher than a candle, because a diffuser relies on evaporation alone rather than heat.

How much fragrance oil for a 100 ml diffuser?

About 21 ml at a 25% load, assuming the bottle fills to 85%. The remaining 64 ml is base.

Why is my diffuser cloudy?

The fragrance oil hasn't fully dissolved in the base. Most common with vanilla-heavy and resinous fragrances in plain DPG. A ready-made base with a solubiliser usually fixes it; otherwise the fragrance isn't suitable for diffusers.

How long should a reed diffuser last?

A 100 ml diffuser in a DPG base typically runs two to three months with the reeds flipped weekly. Alcohol-based blends run considerably shorter.

Reed diffuser calculator