Into 30 ml of a carrier oil pour a total of 12 to 15 drops of essential oil.
If you are using several essential oils make sure the total of all the essential oils does not exceed 15 drops for every 30 ml. E.g. 30 ml jojoba plus 5 drops of cedarwood plus 5 drops of rosemary plus 5 drops of thyme.
Examples of carrier oils: jojoba, avocado oil, argan oil, sweet almond oil, castor oil, fractionated coconut oil etc.