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Free health tool

Running speed converter

Convert an existing speed between km/h and mph without estimating pace, effort, fitness or training zones.

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Calculate your result

Enter one non-negative speed without a unit or thousands separator. Use a full stop when a comma with three following digits could be ambiguous.

Accepted range: 0 to 500 km/h

Your result will appear here

Nothing is saved or added to the URL.

What this result means

Choose the speed unit you have and enter one value. The converter uses 1 mph = 1.609344 km/h and the exact inverse. It changes the unit only; it does not judge effort or fitness. [1][2]

What km/h and mph mean

Kilometres per hour and miles per hour express the same quantity—speed—using different distance units over one hour. [1][2]

Why 1 mph equals 1.609344 km/h

The international mile is exactly 1.609344 kilometres. Because both speed units use the same one-hour time interval, the same exact factor converts mph to km/h. [1]

Speed is not the same as pace

Speed is distance per unit of time, such as km/h. Running pace is time per unit of distance, such as minutes per kilometre. This page converts speed units only; it does not calculate pace. [2]

Why a device may show a slightly different number

A treadmill or wearable may round its original speed. This tool calculates from the value entered and rounds the converted display to two decimals. [1]

What this conversion cannot tell you

Changing km/h to mph cannot determine effort, fitness, training suitability, calorie use, device accuracy or whether an activity is safe for a person.

Formula and assumptions

Formula
mph = km/h ÷ 1.609344. km/h = mph × 1.609344. [1][2]
Version
International-mile speed conversion, nist-kmh-mph-v1
Rounding
Use the exact international-mile relationship and round once for display to two decimal places.
Worked example
For 12 km/h: 12 ÷ 1.609344 = 7.456454… mph, displayed as 7.46 mph. For 7.5 mph: 7.5 × 1.609344 = 12.07008 km/h, displayed as 12.07 km/h. [1]

Who this is for — and when not to use it

Intended use

Neutral unit conversion of one existing speed from a run, walk, treadmill, wearable or activity record.

Not intended for

This tool does not calculate pace from time and distance, prescribe treadmill settings, judge fitness or effort, create training zones, estimate calories, or assess whether activity is safe.

Exclusions

  • Pace, distance or finish-time calculation
  • Training-zone, fitness or performance classification
  • Exercise prescription or treadmill safety decisions
  • Calorie or energy-expenditure estimates
  • Medical or symptom-based exercise guidance

Evidence sources

  1. 1. NIST Guide to the SI, Appendix B: Conversion Factors — National Institute of Standards and Technology. Accessed Aug 9, 2026.
  2. 2. SP 330 - Section 2 — National Institute of Standards and Technology. Accessed Aug 9, 2026.