To figure it out on a computer, you need the missing item, RPM. There are sites that help you figure this stuff but you need: gears in back, diameter of tires, speed & rpm.

Otherwise do it the most common way. Have someone follow you with cel phones turned on. If you don't trust their car, do it with another car.

When I'm doing this I have my wife or one of my kids follow me around my special loop. I end up knowing what speed or RPM I'm running in either the truck or Mustangs by a very small error %.


Craig

My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear
My truck ....... Respect The Rust
If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.