A teaspoon is 5ml, a tablespoon is 15ml.
I've given my 7lb dog benedryl pills before, I give her 1/4 of a pill. My vet told me that dose is correct.
This website says to divide the dogs weight by 2.5, so 7/2.5=2.8. A teaspoon is 5ml, so I'd give him 1/2 teaspoon.
http://culverpalmsanimalhospital.com...s/Benadryl.pdf
They also agree with giving 1/4 of a pill for a dog this size.