Running Pace Calculator Calculators
Convert between pace, speed and finish time for any distance.
Running Pace Calculator is a free online tool that convert between pace, speed and finish time for any distance. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Calculators
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 5
- Works offline
- Yes, after the first visit
About Running Pace Calculator
Projected times here assume you hold the same pace over every distance, which nobody does — race pace falls as distance rises. Riegel's formula suggests your marathon pace is typically 5–8% slower than your half-marathon pace, so treat the longer projections as optimistic ceilings.
How to use it
- Enter distance, custom distance (km) and target hours.
- Adjust the remaining 2 settings if the defaults do not fit your case.
The 5 settings
| Setting | What it does | Default |
|---|---|---|
| Distance | Choose from 5: 5K, 10K, Half marathon, Marathon, Custom. | 10K |
| Custom distance (km) | A numeric value. | 15 |
| Target hours | Range 0–48. | 0 |
| Target minutes | Range 0–59. | 50 |
| Target seconds | Range 0–59. | 0 |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Distance, Custom distance (km), Target hours, Target minutes, Target seconds |
Questions
How do I convert between kilometers and miles pace?
A mile is 1.609344 km, so mile pace is km pace multiplied by that. A 5:00/km pace is 8:03/mile — the tool shows both so you do not have to.
What does the distance option change?
It offers 5 choices — 5K, 10K, Half marathon and Marathon and more. The default is 10K, which suits most cases; change it when your input or your destination calls for something specific.
What are the limits on target hours?
It accepts 0 to 48, starting at 0. The other numeric controls have their own ranges: target minutes 0–59, target seconds 0–59.
Is the arithmetic exact?
It uses double-precision floating point — about 15 significant figures, far more than the inputs justify. Displayed rounding is cosmetic; the underlying numbers are not rounded between steps, so chained results do not drift.