size?
Don't know what size you have.
With tire removed, lay a straight edge across the face of the wheel hub then with a ruler measure from the straight edge back to the frame rail or inner fender and subtract 1" for clearance of the tire, thats your off-set.
For the front off-set make sure the steering wheel is centered before measuring.
To measure the wheel off-set, with the wheel on the ground up-side down, lay a straight edge across the rim (not the tire) and measure down to the wheel mounting face.