How the pace converter works
Every format, one arithmetic
Pace and speed are reciprocals: 8:00/mile = 60/8 = 7.5 mph = 12.07 km/h = 4:58/km. The calculator does the reciprocal math and shows the treadmill equivalent — where belt speed is mph/kmh and the grade setting matters more than most runners realize.
The treadmill grade rule
Indoor running lacks air resistance; a 1% grade approximates outdoor energy cost at typical training speeds. At faster efforts (6:00/mile and under), 1.5–2% is the closer match. Zero-grade treadmill runs feel easier than the watch claims — which is why treadmill "PRs" deserve an asterisk, and why the calculator includes a grade-adjusted pace estimate using the standard (ACE/Jones-style) correction.
Race-equivalent context
The output labels what your pace roughly equals for common race distances — useful sanity checks when converting a treadmill interval session to the road, or when a coach prescribes "10K pace" and you have never raced 10K. Treat the labels as neighborhood estimates: real equivalences depend on your endurance base, which is what the race predictor models properly.