What is the fromula to calculate the volume of a washer?

create your own formula

you would have to know the radius to the outside of the washer and the radius to the inside of the washer as well as its thickness
Outer radius --> r1
inner radius --> r2
thickness ----> h

Volume = pi(r1)^2(h) - pi(r2)^2(h)
= pi(h)(r1^2 - r2^2)