How to use (3 steps)
- Choose what to solve: distance, time, or pace/speed. Pick a race preset to fill distance when applicable.
- Enter the other two values with their units. Use hh:mm:ss for time and min/km or min/mile for pace.
- Results update automatically, including speeds and lap splits. Copy results or a share URL when you’re happy.
Seconds are rounded; pace and speed are shown in both km and mile terms.
Presets fill the distance field when distance is an input (time or pace modes).
Inputs
Adjust the fields you need—results recalc automatically. Keep numbers simple; commas are allowed.
Enter or adjust values to see distance, time, pace, and speed.
Seconds are rounded; speeds and distances show 2 decimals.
Splits
Rounded to whole seconds. Lap distances show 2 decimals.
| Distance | Elapsed time |
|---|
What these results mean
Estimates assume a steady pace with no stops. Lap tables use the calculated pace and round to whole seconds.
Use the share URL to keep your exact inputs. Adjust lap spacing to see key split times for your race plan.
How it’s calculated
- pace = time ÷ distance, speed = distance ÷ time, and distance = speed × time.
- Time is converted to seconds and distance to kilometers internally; miles use 1 mile = 1.609344 km.
- min/mile ↔ min/km pace is converted via the same factor. Speed is shown in km/h and mph.
- Seconds are rounded to the nearest whole second before showing hh:mm:ss or pace; speeds and distances show 2 decimals.
FAQ
Should I enter pace as min/km or min/mile?
Use min/km for most international races and min/mile if you think in miles. The calculator converts both ways and also shows km/h and mph.
How are pace and speed converted?
Pace is kept in seconds per kilometer internally. min/mile is converted using 1 mile = 1.609344 km. Speed is distance divided by time, then shown in km/h and mph rounded to 2 decimals.
How do I plan a sub-4 marathon or other targets?
Select time mode, pick the marathon preset (42.195 km), and type your goal time (e.g., 4:00:00). You’ll see the required pace per km/mile and average speed.
Is anything stored or sent to a server?
No. Calculations stay in your browser. Copy the share URL only when you want to keep or send your inputs.