# Pace Calculator

> Running pace is your time divided by your distance. A 2-hour half marathon works out to 5:41 per km or 9:09 per mile. Enter any two of distance, time and pace to get the third, with speed, even splits and predicted times for other race distances.

- Interactive calculator: https://calculatorswithsteps.com/pace-calculator
- Category: Health & Fitness Calculators
- Last updated: 2026-11-10
- Publisher: Calculators With Steps (calculatorswithsteps.com)

## How to use the pace calculator

1. Choose what you want to work out: your **pace** for a race or any distance, your **finish time** at a given pace, or the **distance** you covered from your time and pace.
2. Pick **per km** or **per mile**. This sets the unit for pace input, the splits table and the main result. Both paces are always shown.
3. Enter your time as hours, minutes and seconds, and your pace as minutes and seconds.

You get pace per km and per mile, speed in km/h and mph, an even-pace splits table and predicted times for 1 mile to the marathon.

## Pace formula

**Pace = time ÷ distance**

**Time = pace × distance**

**Distance = time ÷ pace**

**Speed (km/h) = distance in km ÷ time in hours**, or 60 ÷ pace in minutes per km

Work in seconds to avoid mistakes. A 2:00:00 half marathon is 7,200 seconds over 21.0975 km, so pace = 7,200 ÷ 21.0975 = 341.27 seconds per km. That is 5 minutes and 41 seconds per km. Multiply by 1.609344 for pace per mile: 549 seconds, or 9:09 per mile.

## Worked example: a 2-hour half marathon

| Result | Value |
| --- | --- |
| Pace per km | 5:41 |
| Pace per mile | 9:09 |
| Speed | 10.55 km/h (6.55 mph) |
| 10 km split | 56:53 |
| 21 km split | 1:59:27 |

The calculator also predicts other races from this result with Riegel's formula: 26:05 for 5K, 54:23 for 10K and 4:10:12 for the marathon.

## Common race paces

| Goal | Distance | Pace per km | Pace per mile | Speed |
| --- | --- | --- | --- | --- |
| 30:00 5K | 5 km | 6:00 | 9:39 | 10 km/h |
| 25:00 5K | 5 km | 5:00 | 8:03 | 12 km/h |
| 1:00:00 10K | 10 km | 6:00 | 9:39 | 10 km/h |
| 55:00 10K | 10 km | 5:30 | 8:51 | 10.91 km/h |
| 1:45:00 half | 21.0975 km | 4:59 | 8:01 | 12.06 km/h |
| 2:00:00 half | 21.0975 km | 5:41 | 9:09 | 10.55 km/h |
| 3:30:00 marathon | 42.195 km | 4:59 | 8:01 | 12.06 km/h |
| 4:00:00 marathon | 42.195 km | 5:41 | 9:09 | 10.55 km/h |
| 5:00:00 marathon | 42.195 km | 7:07 | 11:27 | 8.44 km/h |

## Pace to speed conversion for treadmills

Treadmills show speed, while running apps and race plans use pace. Use this table to switch between them.

| Pace per km | Pace per mile | Speed (km/h) | Speed (mph) |
| --- | --- | --- | --- |
| 4:00 | 6:26 | 15 | 9.32 |
| 5:00 | 8:03 | 12 | 7.46 |
| 6:00 | 9:39 | 10 | 6.21 |
| 7:00 | 11:16 | 8.57 | 5.33 |
| 8:00 | 12:52 | 7.5 | 4.66 |

The same formulas work for walking. A pace of 9:00 per km is 6.67 km/h (4.14 mph), and 12:00 per km is 5 km/h (3.11 mph).

## Predicting race times with Riegel's formula

Peter Riegel, an American research engineer, published this model in Runner's World in 1977 and expanded on it in American Scientist in 1981:

**T2 = T1 × (D2 ÷ D1)^1.06**

T1 is your time over distance D1, and T2 is the predicted time over D2. The exponent 1.06 means each doubling of distance costs a little more than double the time, because you have to slow down. A 25:00 5K predicts 52:07 for 10K, 1:55:00 for the half marathon and 3:59:47 for the marathon.

Keep its limits in mind:

- Riegel fitted it to events lasting roughly 3.5 to 230 minutes.
- It assumes equal fitness and training for both distances. Most recreational runners run slower in a marathon than a 5K-based prediction suggests.
- Heat, hills and wind change real-world times. Use the prediction as a target, then adjust after a long training run.

## Pacing tips

- **Use even or slightly negative splits.** Starting too fast usually costs more time in the second half than it saves in the first.
- **Print or memorize key splits.** The splits table shows where you should be at every km or mile.
- **Set treadmill speed from pace.** 60 ÷ pace in minutes per km gives km/h. For example, 5:00 per km is 12 km/h.
- **Track effort, not only pace.** On hot or hilly days, run by heart rate or feel. The [target heart rate calculator](https://calculatorswithsteps.com/target-heart-rate-calculator) gives your training zones.
- **Fuel for the distance.** The [calories burned calculator](https://calculatorswithsteps.com/calories-burned-calculator) estimates how much energy a run uses, and the [TDEE calculator](https://calculatorswithsteps.com/tdee-calculator) shows your total daily needs.

## Frequently asked questions

### How do I calculate my running pace?

Divide your time by your distance. A 10K in 55 minutes is 55 ÷ 10 = 5.5 minutes per km, which is 5:30 per km or 8:51 per mile. Convert the decimal part to seconds by multiplying by 60.

### What pace do I need for a sub-2-hour half marathon?

You need to average 5:41 per km or 9:09 per mile for the 21.0975 km course, a speed of 10.55 km/h (6.55 mph). Running exactly 6:00 per km would bring you home in 2:06:35.

### What pace is a 4-hour marathon?

A 4-hour marathon is 5:41 per km or 9:09 per mile, the same pace as a 2-hour half marathon because the marathon is exactly twice as long. A 3:30 marathon needs 4:59 per km or 8:01 per mile.

### How do I convert pace per km to pace per mile?

Multiply the pace per km by 1.609344, the number of kilometers in a mile. A 5:00 per km pace becomes about 8:03 per mile, and a 6:00 per km pace becomes 9:39 per mile.

### How do I turn pace into treadmill speed?

Divide 60 by your pace in minutes. A 6:00 per km pace is 60 ÷ 6 = 10 km/h, and a 10:00 per mile pace is 6 mph. Many runners add a 1% incline to make treadmill running feel closer to running outdoors.

### How accurate is the Riegel race time formula?

It works best for efforts between about 3.5 and 230 minutes and for distances close to the one you raced. It assumes you are equally trained for both, so predicting a marathon from a 5K is often too optimistic. A 25-minute 5K predicts a 3:59:47 marathon, which most runners only reach with solid long-run training.

### How long are a half marathon and a marathon?

A half marathon is 21.0975 km (13.1 miles) and a marathon is 42.195 km (26.2 miles). A 5K is 3.11 miles and a 10K is 6.21 miles.

## Sources

- [Riegel, P. S. (1981). Athletic Records and Human Endurance. American Scientist 69(3)](https://www.jstor.org/stable/27850427)
- [Wikipedia – Peter Riegel and the race time prediction formula](https://en.wikipedia.org/wiki/Peter_Riegel)

> Disclaimer: results are estimates for information and education, not medical advice. Confirm important decisions with a qualified professional.