I could never find good dilution tables in aromatherapy books so I made my own. Maybe you will find them useful.
A lot of AT books say to use so many drops of essential oil (EO) per ml or oz. of carrier oil. The problem is that drops vary widely between oils. Most of my books use the arbitrary number of 20 drops per ml of EO because water almost always has 20 drops/ml. However, while that works for water because of its high surface tension and special physical characteristics, it’s wildly unreliable for EOs. I guess the book authors never bothered to try counting drops? I’ve gotten anywhere from 20 to 45 drops in a ml of oil, depending on both the oil and the dropper.
The other thing I don’t like about the books is the dilutions are often more concentrated than I use. In aromatherapy, less is often more. Lotions and massage oils with dilutions at 1% or below are gentle and still have plenty of fragrance. I only use higher concentrations for shortterm, very specific applications. My tables have the lower dilutions.
Kitchen cups and measuring spoons work fine. You’ll probably want a separate set so you’re not getting oils in your food. Glass or metal is best because it comes completely clean. If you only have plastic, dunk the measuring spoon in some rubbing alcohol right after you measure and most oils will come off, though eventually your spoons might get smelly. As an alternative, I find the disposable plastic droppers sold by many aromatherapy suppliers easier to use than spoons. Some are even marked in 0.5 ml increments for easy measuring.
These are my tables in English and metric measurements. Unfortunately, to accurately measure a 0.5% or lower dilution, it’s necessary to make quite a bit of a blend or use a trick called serial dilution that I’ll explain below. To use this table, start by reading down the left hand side to find the amount of carrier oil you want to use. Then read across to the right and find the column with the right dilution to determine the amount of essential oil.
English measurements, in both tsp. and ml for droppers:
Carrier Oil  Essential Oil Dilution  
2%

1%

0.5%


2 Tbsp. (1 oz) 
1/8 tsp.
(0.6 ml) 

1/4 cup (2 oz) 
1/4 tsp.
(1.25 ml) 
1/8 tsp.
(0.6 ml) 

1/2 cup (4 oz) 
1/2 tsp.
(2.5 ml) 
1/4 tsp.
(1.25 ml) 
1/8 tsp.
(0.6 ml) 
1 cup (8 oz) 
1 tsp.
(5 ml) 
1/2 tsp.
(2.5 ml) 
1/4 tsp.
(1.25 ml) 
And for the rest of the world on the lovely metric system:
Carrier Oil  Essential Oil Dilution  
2%

1%

0.5%


25 ml 
0.5 ml


50 ml 
1.0 ml

0.5 ml


100 ml 
2.0 ml

1.0 ml

0.5 ml

250 ml 
5 ml

2.5 ml

1.25 ml

The trick to making less of a 0.5% blend is to do the dilution in two steps. First, put 1/8 tsp. of oil into 3/8 tsp. of carrier oil. (Or 0.5 ml essential oil into 1.5 ml carrier oil) That makes a bit of essential oil diluted by a fourth. Second, use the charts above as if you were making 2% oil, but measure from the diluted oil you just mixed up instead. The final blend will be at 0.5%, and it’s possible to make only 2 Tbsp. Follow the 1% chart for an even lower 0.25% blend.
For even smaller amounts of blends, measuring dropwise is helpful. First, determine how many drops of essential oil are in a tsp., or a ml. To do this, carefully count the drops it takes to fill 1/8 tsp., or count how many drops fall from 0.5 ml in a calibrated dropper and write it down. Second, figure out how many drops of essential to use for 5 or 10 ml of your blend. Remember that each oil and dropper combination will give you a different drop volume.
These tables are intended for hobby use. Given that kitchen ware is not manufactured to scientific precision, I decided the simplicity of working with full cups of carrier oil was better than complicated, perfect measurements. If you check the math, you’ll find for example that the large volume 2% dilution is actually 2.04% on the American table and 1.96% on the Metric table since for 5 ml of EO they use 240 and 250 ml of carrier oil respectively. If you are making blends to sell, you would probably want to calculate accurate dilutions (like 5 ml in 245 ml for 2% v/v) and measure in scientific glassware or work by weight.