Pace ↔ Speed Converter (min/km, km/h, mph)
Two-way converter between running pace (min/km, min/mile) and speed (km/h, mph, m/s), with race time projections from 5K to the marathon.
How to use
- Type a pace into min/km or min/mile (format mm:ss like 4:30) or a speed into km/h, mph, m/s, or knot — every other field updates live.
- Read the race time projections — what time you'd hit at this pace for distances from 100 m to the marathon.
- Hit a preset (walking, jogging, marathon goal pace, road-bike, highway, …) to jump to a known reference speed.
- Use the copy button to grab the whole report as plain text.
About this tool
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Runners think in pace (minutes per kilometer or mile), cyclists and drivers think in speed (km/h or mph), sailors think in knots, and physicists think in m/s. This converter ties all six together — edit any field and the rest update instantly, including projected finish times for the seven canonical race distances from a 100 m sprint to a 42.195 km marathon. Pace inputs accept the natural mm:ss format ('4:30' for 4 min 30 s per km) and round-trip cleanly to one-tenth of a second. The conversion factors use the exact international definitions: 1 mile = 1609.344 m, 1 knot = 1.852 km/h = 0.5144… m/s. Race distances follow the IAAF / World Athletics certifications, so the marathon is exactly 42 195 m and the half marathon exactly 21 097.5 m. Useful for race-day pacing strategy, treadmill setting conversion, GPS-watch sanity checks, or just figuring out whether your 13 km/h workout actually translates into a sub-3-hour marathon (spoiler: it doesn't, you'd need 14.07 km/h).
Frequently asked questions
Why is my treadmill set to 12 km/h not a 5:00 min/km pace?
It is — 12 km/h equals exactly 5:00 min/km because 60 / 12 = 5. The conversion is pace_min_per_km = 60 / speed_km_per_h. Common slip-ups: 10 km/h is 6:00 min/km, not 6:30; 15 km/h is 4:00 min/km, not 4:30. Each 1 km/h step from 10 down isn't a 30-second pace step.
How accurate is the marathon projection?
Mathematically exact — it's just distance ÷ speed — but real marathons rarely follow a single pace. Most runners slow 5–15 % over the last 12 km ('positive split'), so a flat-pace projection underestimates real finish time. Elite negative-split runs (Bekele, Kipchoge) are the exception, not the rule. Use the projection as an upper bound from your steady-state ability, then subtract a realistic fade factor.
Why both knot and km/h?
A knot is one nautical mile per hour, and a nautical mile is exactly 1852 m — chosen because it equals one minute of arc along any meridian, which is the unit sailors actually navigate in. Aviation also uses knots for airspeed. Knot ≠ km/h: 100 knots is 185.2 km/h, not 100.
Why don't running paces use seconds-per-meter?
They could, and on a track session a 4-minute mile prints as 14.9 s/100 m, but for an entire race the numbers get awkward fast. min/km gives readable values from a brisk walk (15:00) to a world-class marathon (2:48). It's a cultural convention more than a technical choice — strict SI would use m/s.
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