Pace, time and distance formulas
Pace = Time ÷ Distance
Time = Pace × Distance
Distance = Time ÷ Pace
Time = Pace × Distance
Distance = Time ÷ Pace
1 mile = 1.609344 km. To convert a pace per kilometer to a pace per mile, multiply by 1.609344; to go the other way, divide.
Example: You run a 10K in 50:00. Your pace is 50 ÷ 10 = 5:00 per km, or 5:00 × 1.609 = 8:03 per mile, a speed of 12 km/h (7.5 mph). Using Riegel’s formula, a 25:00 5K predicts about 52:07 for 10K, 1:55:00 for a half marathon and 3:59:47 for a marathon.
Common race pace targets
| Goal | Pace per km | Pace per mile |
|---|---|---|
| 5K in 30:00 | 6:00 | 9:39 |
| 10K in 60:00 | 6:00 | 9:39 |
| Half marathon in 2:00:00 | 5:41 | 9:09 |
| Marathon in 4:00:00 | 5:41 | 9:09 |
| Marathon in 3:30:00 | 4:59 | 8:01 |
Planning training time? The time duration calculator adds up sessions for you.
How to use the calculator
- Choose what you want to find: pace, finish time or distance.
- Enter the other two values. Times can be entered as hours, minutes and seconds.
- Choose kilometers or miles. The result shows pace per km and per mile, speed and race-time predictions.
Pace and finish time chart
| Pace | Per mile | 5K | 10K | Half marathon | Marathon |
|---|---|---|---|---|---|
| 5:00 /km | 8:03 /mi | 25:00 | 50:00 | 1:45:29 | 3:30:58 |
| 5:30 /km | 8:51 /mi | 27:30 | 55:00 | 1:56:02 | 3:52:04 |
| 6:00 /km | 9:39 /mi | 30:00 | 1:00:00 | 2:06:35 | 4:13:10 |
| 6:30 /km | 10:28 /mi | 32:30 | 1:05:00 | 2:17:08 | 4:34:16 |
Predicting race times
The calculator uses Peter Riegel’s formula, published in 1977 and still widely used: T₂ = T₁ × (D₂ ÷ D₁)1.06. It assumes you train properly for the longer distance. Predictions are most reliable between similar distances — a 10K time predicts a half marathon better than a 5K predicts a marathon. Many first-time marathoners run slower than predicted because endurance, fueling and pacing matter more over 42 km.
Training paces
Most of your running should be easy. Coaches commonly suggest these effort levels, relative to your current race pace:
- Easy runs: conversational effort, often 60–90 seconds per mile (40–55 s per km) slower than marathon pace.
- Marathon pace: comfortably hard, sustainable for hours.
- Threshold (tempo) pace: roughly the pace you could hold for about an hour of racing — “comfortably hard”.
- Interval pace: around 5K race pace or slightly faster, in repeats of 2–5 minutes with recovery.
Pacing on race day
- Start conservatively. Adrenaline makes the first kilometer feel easy; going out 10 seconds per km too fast often costs minutes later.
- Aim for even or negative splits — the second half equal to or slightly faster than the first.
- Adjust for conditions: heat above about 60 °F (15 °C), humidity, wind and hills all slow you down. GPS watches can also measure courses slightly long because of tangents.
Frequently asked questions
How do I calculate running pace?
Divide your total time by the distance. A 10 km run in 50 minutes is 50 ÷ 10 = 5 minutes per kilometer. To convert to minutes per mile, multiply the per-kilometer pace by 1.609: 5:00/km ≈ 8:03/mile.
What pace do I need for a sub-4-hour marathon?
A 4-hour marathon requires an average of 9:09 per mile or 5:41 per kilometer. Most runners aim a few seconds faster to allow for water stations and crowding.
How accurate are the race time predictions?
Predictions use Peter Riegel’s formula, T₂ = T₁ × (D₂ ÷ D₁)1.06. They work best for distances within a factor of about four of your known race and assume equal training for the longer distance. Marathon predictions from a 5K are often optimistic for less-experienced runners.
What is a good running pace for a beginner?
Many beginners run between 10 and 13 minutes per mile (6:15–8:05 per km). An easy pace — one at which you can hold a conversation — is the right pace for most training runs.
What is a good pace for a beginner?
Many beginners run between 6:00 and 7:30 per km (about 10–12 minutes per mile). The right pace is one where you can still speak in short sentences.
How do I convert km pace to mile pace?
Multiply by 1.609. A 5:00 per km pace is about 8:03 per mile.