Convert speed between feet per second and statute miles per hour.
The code uses the exact rational 1 mph = 22/15 ft/s, so ft/s → mph multiplies by 15/22 and the inverse divides by that factor. Inputs must be non‑negative.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.