Running Speed Calculator
Convert running pace to speed (km/h and mph) and back, with finish times for 5K, 10K, half marathon and marathon.
Your inputs
Results
Speed
12 km/h
- Speed
- 7.46 mph
- Pace per km
- 5:00
- Pace per mile
- 8:03
✓Exact calculation — rounded only for display
| Race | Time |
|---|---|
| 5K | 25:00 |
| 10K | 50:00 |
| Half marathon | 1:45:29 |
| Marathon | 3:30:59 |
Inputs are never added to links for financial, salary or health calculators.
What this calculator does
Treadmills show speed while race plans use pace; this tool converts between them and projects race times at the same pace.
Formula and method
Worked example
Calculated by this tool with its default inputs:
Inputs
- Convert: Pace → speed
- Pace (mm:ss): 5:00
- Per: Kilometres
Results
- Speed: 12 km/h
- Speed: 7.46 mph
- Pace per km: 5:00
- Pace per mile: 8:03
How to read the results
Finish times assume the same pace for the whole distance.
Assumptions and limitations
- Treadmill and outdoor running feel different at the same speed.
Health results are general estimates for adults and do not replace medical advice, diagnosis or treatment. Speak to a qualified health professional about your personal situation, especially during pregnancy or if you have a medical condition.
Questions
Why does 12 km/h equal 5:00 per km?
Because 60 minutes ÷ 12 km = 5 minutes per km.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Because this calculator can involve personal financial or health details, your inputs are never added to share links or saved to history. Privacy policy