The Benadryl dose is 2 to 4 mg per kilogram. The liquid for children is 2.5 mg per ml.
2 mg/kg = 0.9 mg per pound = 0.36 ml per pound of body weight
4 mg/kg = 1.8 mg per pound = 0.73 ml per pound of body weight
Source:
https://www.justanswer.com/bird-vet/8twu4-benadryl-safe-parrot.html
