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A lot of Aromatherapists say to use so many drops of essential oil per ml or oz. of carrier oil. The problem with measuring this way is that drop sizes vary from oil to oil and container to container. Most books and websites use the arbitrary number of 20 drops per ml of oil, because water almost always has 20 drops per ml. However, while 20 drops per ml works great for water because of it's high surface tension and special physical characteristics, 20 drops/ml of essential oil is just not reliable. There is anywhere from 20 to 45 drops in a ml of oil, depending on both the oil and the dropper. That kind of difference can change a safe 2% blend into a sensitizing 4% blend.
It's really important to measure accurately. If a blend is too concentrated, it can sensitize or irritate the skin. Too diluted, and a blend may not have quite the intended therapeutic effect. Measuring accurately without making assumptions like 20 drops/ml makes it necessary to measure larger volumes like 1/2 ml or 1/8 tsp. (0.63 ml) and use more carrier oil. Making more of a blend is a little more expensive, but remember that sensitization is lifelong. It just isn't worth risking sensitization or irritation to save a bit of money.
Normal kitchen measuring cups and spoons work fine for measuring essential and carrier oils. Buy a separate set of measuring spoons for essential oils and don't use them for food. Metal spoons are easiest because the essential oil will clean right off. For plastic spoons, dunk the measuring spoon in some rubbing alcohol right after you measure the essential oil and most oils will come off. Eventually, though, plastic spoons will accumulate too much fragrance and need to be discarded. A measuring tool like a calibrated, disposable plastic dropper sold by many aromatherapy suppliers is good to use. With careful alcohol cleaning, the droppers can be reused for a while. Buy the ones that are marked in 0.5 ml increments.
At this point, you're probably wondering what dilution to choose. Here are some very conservative suggestions for beginners ONLY for oils on the Safe Oils list. Please talk to an aromatherapist or read about the oils in this database before using other oils or higher percentage dilutions. For daily or more frequent use, 0.5% or even 0.25% is best to help avoid sensitization. For a normal massage done once a week or so, 1% is fragrant and therapeutic. The 2% dilution is common for occasional aromatherapy massage by an experienced practitioner. A 2% dilution is also good for frequent therapeutic use on smaller areas of the body for less than two weeks. Examples could be easing the pain of overworked muscles, healing burns, or treating a cough with a chest rub.
Below are a couple of tables that list essential oil dilutions in Imperial 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 that is explained below. To use this table, start by reading down the left hand side to find the amount of blend to make. Then read to the right and find the column with the right dilution to determine the amount of essential oil.
English imperial measurements, in both tsp. and ml for droppers:
| Carrier Oil |
Essential Oil Dilution |
| |
2% |
1% |
0.5% |
| 2 Tbs. (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) |
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 wee 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 Tbs. Follow the 1% chart for an even lower 0.25% blend.
For even smaller amounts of blends, measuring dropwise is helpful. However, it is necessary to 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. From there it's pretty easy to figure out how many drops of essential oil to use for 5 or 10 ml of an accurately diluted blend. Remember that each oil and dropper combination changes the drop volume.
Nitpickers might have noticed that we've used 5 ml in 240 ml of carrier on the imperial measurements table and 250 ml of carrier on the metric table. Just to demonstrate that we do understand maths, these dilutions are 2.04% and 1.96% respectively. Both are 2.0% to a reasonable two significant figures for measurement of essential oil in a cheap plastic pipette or poorly calibrated measuring spoon. To be more precise (unnecessary unless you hapen to be selling blends), measure out 245 ml of carrier per 5 ml of essential oil in good, glass graduated cylinders.
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