Dilutions

Desired % Of Essential Oil Number Of Drops Of Essential Oil per Volume of carrier oil
  5ml 10ml 15ml 30ml
0.4 0.6 1.2 1.8 3.6
0.5 0.75 1.5 2.25 4.5
0.6 0.9 1.8 2.7 5.4
0.7 1 2 3 6.3
0.8 1.2 2.4 3.6 7.2
0.9 1.35 2.7 4 8
1.0 1.5 3 4.5 9
1.5 2.25 4.5 6.75 13.5
2.0 3 6 9 18
2.5 3.75 7.5 11.25 22.5
3.0 4.5 9 13.5 27
3.5 5.25 10.5 15.75 31.5
4.0 6 12 18 36
4.5 6.75 13.5 20.25 40.5
5.0 7.5 15 22.5 45

 In order for essential oils to be used safely, most need to be diluted properly in a carrier oil. Undiluted essential oils can cause skin sensitization, rash, burns, etc. 

There are several to choose from, coconut oil, jojoba oil, aloe vera oil, sweet almond oil and many more.  Each has their own benefits so choose the carrier oil that will work for your specific purpose. 

Example of dilutions: Bergamot essential oil safe dilution is 0.4%

If you wanted to dilute in 5ml (1 tsp) of carrier oil you would use 0.6 drops. Since you cannot do this you would just dilute to 1 drop per 5ml carrier oil. 

If you wanted to use 10ml (2 tsp) carrier oil then you would use 1.2 drops of Bergamot. At this point you could choose whether you wanted to round up and use two drops or round down and use one drop.