All drops are NOT created equal. The size and weight of a drop will vary depending on the oils

viscosity, temperature, and the size and type of dropper used.

The standard used in most printed books for aromatherapy is 20 drops per mL, This comes from the

“Standard” eye dropper and water. Most “standard” eye droppers can vary from 18-26 drops per mL.

When ‘Standard” formulas are given without reference to specific dropper the 20 drops per mL is

generally what is referred to.

Many of the “Drop method” formulas are generated with the Essential oil portion in drops and the

carrier part in a volumetric measurement, i.e. mL, Fluid ounces, teaspoons etc.

This is the simplest method to use when working with a very small batch. Your results are mainly

dictated by using the same dropper and working slowly and accurately.

To get the best results from this method you need to ensure your dropper is the same as the “Standard”

dropper and if not adjust the formula to compensate. If you change the type of dropper size or shape the

balance in your formula can also change.

Unfortunately there is no way of knowing how many drops per mL your dropper is going to deliver,

unless you sit down and calibrate the dropper that you are going to use.

First you will need a accurate graduated pipette that has a 1 mL mark.

Step 1: Suck up 1 mL of water into the pipette, and empty the pipette into a small vial.

Step 2: Suck up the 1 mL of water from the small vial into your dropper.

Step 3: Carefully count the drops from the dropper. Be sure to use the same pressure delivering each

and every drop, since a change in pressure can also change the size of the drop and hence the number

of drops per mL will also change.

Do this procedure several times and average your results together, this will give you the number of

drops per mL for your dropper.

Do this same procedure for each of the Essential oils you are going to use and keep it as a reference of

drops per mL for each of the oils.

The standard formulas are generated for 20 drops per mL. If your dropper is not 20 drops per mL you

will have to adjust your formula to compensate for the difference.

By performing the calibration routine above lets say we find that our eye dropper is 25 drops per mL

and the formula is written for 20 drops per mL.

Our formula example has 40 drops of essential oil at the standard 20 drops per mL, hence 2 mL of

essential oils.

Our dropper is producing 25 drops per mL, so to get the same results we need to adjust the formula.

We can not measure fractions of a drop so we have to adjust the total amount of formula being

produced and keep the number of drops constant. Our new dropper has more drops per mL so each

drop is smaller than the 20 drop per mL standard dropper by 20 %.

The old formula made 2 mL of essential oils (20 drops per mL, 40 drops total). Our new formula will

produce 20% less; 1.6 mL of essential oil. To keep the ratio of essential oil to carrier the same we will

reduce the amount of carrier by the same amount 20%. The original formula had 8 mL of carrier so our

adjusted formula will yield 6.4 mL of carrier. This formula now makes 8 mL total while taking into the

consideration the calibration of our dropper.

Original formula Adjusted Formula

Formula 1 = 10 mL total                                                Formula 1A = 8 mL total

Oil 40 Drops (2 mL total)                                               Oil 40 Drops (1.6 mL total)

A 9                                                                                  A   9

B 2                                                                                   B   2

C15                                                                                  C  15

D 14                                                                                 D 14

Carrier: 8 mL                                                                   Carrier: 6.4 mL