CodeKitHubWhat Is This Tool?
A pace calculator converts between three running variables — distance, time and pace — solving for whichever one you don't already know. Pace is usually expressed as minutes per kilometer or minutes per mile: distance ÷ time gives speed, and its inverse gives pace.
It has three modes: distance + time → pace (how fast did I run), pace + distance → finish time (how long will a race take at this pace), and pace + time → distance (how far can I run in this much time at this pace). Runners use all three constantly, whether reviewing a training run or planning race strategy.
Why Use It?
- Three modes in one tool: find pace, predict finish time, or estimate distance.
- Quick-select buttons for 5K, 10K, half marathon (21.1K) and marathon (42.2K) — no need to type the distance.
- Switch instantly between kilometers and miles.
- Useful for planning race splits, checking training paces, or estimating a finish time before race day.
- Runs entirely in your browser — nothing you enter is sent anywhere.
How to Use
- Choose the mode that matches what you know: distance+time, pace+distance, or pace+time.
- Enter the known values, or tap a quick-select button for a standard race distance.
- Switch between km and miles depending on which unit you train in.
- Read the result — pace, finish time or distance — updated instantly as you type.
Example
Input
Distance + time mode: ran 10 km in 50 minutesOutput
Pace: 5:00 min/kmPace = time ÷ distance = 50 minutes ÷ 10 km = 5 minutes per km. At that same pace, a marathon (42.2 km) would take about 3h 31m.
Common race distances and paces
| Distance | Pace 5:00/km | Pace 6:00/km | Pace 4:00/km |
|---|---|---|---|
| 5K | 25:00 | 30:00 | 20:00 |
| 10K | 50:00 | 1:00:00 | 40:00 |
| Half marathon (21.1K) | 1:45:30 | 2:06:36 | 1:24:24 |
| Marathon (42.2K) | 3:31:00 | 4:13:12 | 2:48:48 |
Related tools
For converting a pace or distance between kilometers and miles directly, the mile to km converter and unit converter are the natural companions. To work out a percentage improvement between two race times, the percentage calculator handles that.
→ Mile to KM Converter · Unit Converter · Percentage Calculator
Frequently Asked Questions
How do I calculate pace?
Divide your total time by the distance covered: pace = time ÷ distance. Running 10 km in 50 minutes gives a pace of 5:00 per km (50 ÷ 10). If your time is in hours and minutes, convert it all to minutes first — for example 1h 15m is 75 minutes — then divide by the distance to get minutes per km or mile.
How do I use pace to predict a marathon finish time?
Multiply your pace (minutes per km or mile) by the marathon distance (42.2 km or 26.2 miles). A pace of 5:00 min/km predicts a marathon finish of 5:00 × 42.2 = 211 minutes, or about 3 hours 31 minutes. This assumes you can hold that exact pace for the entire distance — in practice many runners plan a slightly slower pace for a marathon than for a shorter training run, since fatigue tends to slow pace in the final miles.
What's the difference between pace (min/km) and speed (km/h)?
Pace tells you how long it takes to cover one unit of distance (minutes per km or mile) — lower is faster. Speed tells you how much distance you cover in one unit of time (km/h or mph) — higher is faster. They're inverses of each other: speed (km/h) = 60 ÷ pace (min/km). A pace of 5:00 min/km equals a speed of 12 km/h (60 ÷ 5). Runners typically talk in pace, cyclists and drivers typically talk in speed.
How accurate is the finish-time prediction?
It assumes a perfectly even pace across the whole distance, which is a useful planning baseline but not exactly how most races go — many runners fade in the second half, especially at marathon distance, so a prediction based on a shorter recent race (like a 10K) is often a more realistic estimate for a marathon than simply extrapolating your training pace.
Is my data stored anywhere?
No. The calculation runs entirely in your browser with JavaScript; nothing you enter is sent to a server, stored or logged.