This shortcut will give you the volume in mL. The calculation is based on 0.01 mg/kg. Take the patient weight and move the decimal (1) spot to the left for 1:10,000 and (2) spots to the left for 1:1,000.
20 kg patient
Epi 1:10,000 = 2.0 mL (Full Arrest)
Epi 1:1,000 = 0.2 mL (Allergic Reaction)