Running Pace Calculator
Calculate your running pace, time, or distance. Get splits, speed, and race predictions with the Riegel formula.
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10K
Time
Pace (/mi)
Pace
5:30/mi
Speed
10.9 mph
Time
55:00
Race predictions
| Distance | Predicted time | Pace |
|---|---|---|
| 5K | 15:56 | 3:11/km |
| 10K | 33:13 | 3:19/km |
| Half marathon | 1:13:17 | 3:28/km |
| Marathon | 2:32:47 | 3:37/km |
Running Pace Calculator. Pace, time, and distance from any two values.
A running pace calculator finds your pace, finish time, or distance when you enter the other two, showing results in both min/km and min/mi. It also predicts race times at other distances with the Riegel formula and builds per-kilometer or per-mile split tables so you can plan a smart pacing strategy.
What Is Running Pace?
Running pace is the time it takes to cover one unit of distance, expressed as minutes per kilometer (min/km) or minutes per mile (min/mi). A pace of 5:00 min/km means you run each kilometer in exactly 5 minutes. Pace is the inverse of speed: speed tells you how far you travel per hour (for example 12 km/h), while pace tells you how long each unit of distance takes. Lower pace numbers mean faster running.
A running pace calculator finds any one of three variables -- pace, time, or distance -- when you know the other two. If you ran 10 kilometers in 50:00, your pace was 5:00 per kilometer. If you want to finish a marathon (42.195 km) at a 6:00/km pace, you need 4 hours 13 minutes and 10 seconds. Runners use pace to set training targets, plan race strategies, and track fitness improvements over time.
Pace is the preferred metric for runners because it maps directly to the effort you feel on each kilometer or mile. Most GPS watches, race clocks, and training plans are built around pace rather than speed. A 5:00 per kilometer pace, for example, is exactly 12 km/h and brings a 10K home in 50:00 — the same effort read three ways: pace, speed, and finish time.
How to Use the Running Pace Calculator
The calculator works in three modes -- solve for pace, solve for time, or solve for distance. Choose the value you want to find, enter the other two, and the result updates instantly in both metric (min/km, km/h) and imperial (min/mi, mph) units.
1. Solve for pace. Enter a distance and a finish time. Example: 10 km in 50:00 returns a pace of 5:00/km (8:03/mi) and a speed of 12 km/h (7.46 mph). Here pace = time / distance.
2. Solve for time. Enter a distance and a target pace. Example: a marathon (42.195 km) at 6:00/km returns a finish time of 4:13:10. Here time = pace x distance.
3. Solve for distance. Enter a time and a pace. Example: 45:00 at 5:00/km covers 9 km. Here distance = time / pace.
Below the main result, the calculator builds a splits table -- your cumulative target time at every kilometer or mile marker -- so you can see exactly where you should be at each point in the race. Splits are the times recorded for each segment of a run, and checking them keeps you from going out too fast. Alongside the splits, a race-prediction panel estimates your 5K, 10K, half marathon, and marathon times from the effort you entered, using the Riegel formula.
To convert manually between units, multiply miles by 1.60934 to get kilometers, or divide kilometers by 1.60934 to get miles. To turn pace into speed, divide 60 by the pace in minutes: a 5:00/km pace equals 60 / 5 = 12 km/h, and an 8:00/mi pace equals 60 / 8 = 7.5 mph.
Pace, Speed, and the Riegel Race-Prediction Formula
- = Your known race time (the time from a recent race)
- = The distance of that known race
- = The predicted time for the target race
- = The distance of the target race
- = The fatigue-factor exponent, accounting for pace slowdown over longer distances
The two core equations are pure division. Pace is total time divided by distance, and speed is distance divided by total time:
Pace and speed are inverses of one another. A faster runner has a lower pace number (fewer minutes per kilometer) but a higher speed number (more kilometers per hour). A 5:00/km pace is the same effort as 12 km/h; a 6:00/km pace is 10 km/h.
To predict a race time at a distance you have not run yet, the calculator uses the Riegel formula, developed by Peter Riegel and published in Runner's World in 1977 -- the most widely used race-prediction model. The exponent 1.06 is a fatigue factor that reflects how average pace decreases as distance increases: your body accumulates fatigue, and you cannot hold shorter-race intensity over longer distances.
The fatigue factor 1.06 is an average across a broad population of runners. Speed-oriented runners who excel at shorter distances may fit a lower exponent (1.03-1.05), while endurance-focused runners and ultramarathoners may trend toward 1.07-1.10. The formula is most accurate for race durations between about 3.5 minutes and 3 hours 50 minutes, and when the known result comes from a race in the past 2-3 months.
Pace to Finish-Time Chart for 5K, 10K, Half, and Marathon
| Pace (min/km) | Pace (min/mi) | 5K (5 km) | 10K (10 km) | Half (21.0975 km) | Marathon (42.195 km) |
|---|---|---|---|---|---|
| 4:30 | 7:15 | 22:30 | 45:00 | 1:34:56 | 3:09:53 |
| 5:00 | 8:03 | 25:00 | 50:00 | 1:45:29 | 3:30:59 |
| 5:30 | 8:51 | 27:30 | 55:00 | 1:56:02 | 3:52:04 |
| 6:00 | 9:39 | 30:00 | 1:00:00 | 2:06:35 | 4:13:10 |
| 6:30 | 10:28 | 32:30 | 1:05:00 | 2:17:08 | 4:34:16 |
Running Pace Calculation Examples
Solve for pace: a 10 km run in 50:00
You cover 10 km in 50:00 and want your pace. Dividing time by distance: 50:00 / 10 km = 5:00 per kilometer, which is 8:03 per mile. Your speed is 12 km/h (7.46 mph). Your per-kilometer splits climb evenly: 5:00 at 1 km, 10:00 at 2 km, and so on up to 50:00 at 10 km. Holding that same 5:00/km effort, the chart above shows a half marathon would take 1:45:29 and a full marathon 3:30:59 -- if fatigue never grew, which is why the Riegel prediction adds time over longer distances.
Solve for pace: breaking 25 minutes for 5K
You want to run a 5K (5 km) in under 25 minutes. Required pace: 25:00 / 5 km = 5:00 per kilometer (8:03 per mile), a speed of 12 km/h (7.46 mph). Your target splits are 5:00, 10:00, 15:00, 20:00, and 25:00 at each kilometer marker. In training, practice holding 5:00/km on race-pace efforts and run intervals slightly faster -- around 4:30-4:45/km -- to build the speed reserve you need on race day. Easy runs can be a full minute per kilometer slower.
Solve for time: a marathon at 6:00/km
You plan to run the marathon (42.195 km) at an even 6:00/km. Multiplying pace by distance: 42.195 km x 6:00 = 4:13:10, a speed of 10 km/h (6.21 mph, or 9:39 per mile). To pace it evenly, you should pass the halfway mark (21.0975 km) at 2:06:35. If you would rather negative-split, aim to reach halfway a touch slower -- around 2:07 -- and pick the pace up over the final 21 km when you know you can hold it.
Predict a marathon from a half marathon result
You recently ran a half marathon (21.0975 km) in 1:52:00, a pace of about 5:19/km. Because the marathon is exactly double the distance, the Riegel formula gives T2 = 1:52:00 x 2^1.06 = 1:52:00 x 2.0849 = 3:53:31. Your predicted marathon time is roughly 3 hours 53 minutes 30 seconds, at about 5:32/km. That is around 13 seconds per kilometer (21 seconds per mile) slower than your half pace, reflecting the fatigue accumulated over the doubled distance. Predictions are most reliable between adjacent distances like this.
Common Pace Mistakes to Avoid
- Confusing pace with speed. Pace (min/km or min/mi) and speed (km/h or mph) are inverses, not the same number. A 5:00/km pace is 12 km/h, not 5 km/h -- divide 60 by the pace in minutes to get speed.
- Mixing kilometer and mile paces. An 8:00 pace means something very different per mile than per kilometer: 8:00/mi is about 4:58/km. Always confirm which unit a pace, plan, or watch screen is using before you chase it.
- Rounding the race distances. A half marathon is 21.0975 km (13.11 mi), not 21 km, and a marathon is 42.195 km (26.22 mi), not 42 km. At 5:00/km, trimming the half to 21 km hides about 29 seconds; at 6:00/km, trimming the marathon to 42 km hides over a minute (about 1:10).
- Ignoring your splits. Running by feel alone usually means starting too fast. Target even splits (the same pace throughout) or slight negative splits (a faster second half). Most recreational marathoners run positive splits and fade in the closing miles.
- Assuming your 5K pace holds for a marathon. Pace slows as distance grows. A runner who covers 5 km at 5:00/km will realistically average around 5:40/km over a marathon -- roughly 40 seconds per kilometer slower -- because of glycogen depletion and accumulated fatigue.
Pacing Strategies for Training and Race Day
- Base predictions on recent results. The Riegel formula is most accurate with a race time from the past 2-3 months. An old result may not reflect your current fitness, especially if your training volume or intensity has changed.
- Rehearse race pace before race day. Once you know your target pace, add race-pace segments of 3-6 miles to your long runs so your body learns exactly what that effort feels like.
- Start conservatively. The large majority of recreational marathoners run positive splits (a slower second half). Aim for even or slightly negative splits by starting 5-10 seconds per mile slower than goal pace for the first 2-3 miles, then settling in.
- Adjust for terrain and weather. A pace calculator assumes flat ground and ideal conditions. Add roughly 15-20 seconds per mile for hilly courses, and 10-30 seconds per mile for heat above 60F (15C), strong headwinds, or trail surfaces.
- Watch effort, not just pace. Heart rate, breathing, and perceived effort matter as much as the number on your watch. A 5:00/km pace on a hot, humid day costs far more effort than the same pace on a cool morning.
- Use splits to stay honest. Break the race into kilometer or mile checkpoints against your target chart. If you are more than 10-15 seconds ahead of a split early, ease back before it costs you later.
- Predict cautiously across big distance jumps. Riegel is most reliable between similar distances (10K to half marathon). A marathon predicted from a 5K is less trustworthy because marathon results depend on fueling, pacing discipline, and endurance training that short races never test.
- Build speed with tempo runs. A tempo run is a sustained effort at a comfortably hard pace, usually about 25-30 seconds per mile slower than 5K race pace. Tempo work raises your lactate threshold so you can hold faster paces for longer.
- Keep easy runs genuinely easy. Most weekly mileage should feel conversational. A higher VO2 max -- your body's maximum rate of oxygen use -- comes from a mix of easy volume and targeted hard sessions, not from grinding every run near race pace.
Frequently Asked Questions About Running Pace
What is a good running pace for beginners?
A good beginner pace is usually between 10:00 and 13:00 per mile (about 6:13 to 8:05 per kilometer). Most new runners start around 11:00-12:00/mi and get faster with consistent training. For a first 5K, finishing in 30-40 minutes (a pace of 9:39 to 12:52 per mile) is a realistic goal. Aim for a pace where you can still hold a conversation -- if you are too breathless to talk, you are running too fast for an easy run.
How accurate is the Riegel formula for predicting race times?
The Riegel formula is most accurate for race durations between about 3.5 minutes and 3 hours 50 minutes, and when the target distance is within 2-4 times the known race distance. It tends to be optimistic for marathon predictions based on 5K times because it cannot account for fueling, pacing strategy, and endurance-specific training. For the best accuracy, use a race time from the past 2-3 months and predict between adjacent distances (5K to 10K, 10K to half, half to marathon).
What is the difference between pace and speed?
Pace and speed are inverses. Pace is time per distance (5:00 per kilometer), and speed is distance per hour (12 km/h). Runners prefer pace because it maps to the effort of each kilometer or mile. To convert, divide 60 by the pace in minutes, so 5:00/km equals 12 km/h and 8:00/mi equals 7.5 mph.
How do I convert pace from minutes per mile to minutes per kilometer?
To convert min/mi to min/km, divide the pace in seconds by 1.60934. An 8:00/mi pace is 480 seconds; dividing by 1.60934 gives 298 seconds, or 4:58/km. To go the other way, multiply by 1.60934: a 5:00/km pace (300 seconds) becomes 483 seconds, or 8:03/mi.
What pace do I need to run a sub-4-hour marathon?
To finish a marathon in under 4 hours, you need to average 5:41 per kilometer (9:09 per mile) across the full 42.195 km. By the Riegel formula, that lines up with roughly a 1:55 half marathon, a 52-minute 10K, or a 25-minute 5K.
What are negative splits and should I use them?
Negative splits mean running the second half of a race faster than the first. Elite runners favor the strategy because starting conservatively preserves glycogen, limits early oxygen debt, and leaves energy for a strong finish. In practice only a small share of recreational marathoners (studies suggest well under 10%) manage true negative splits, so for most runners even splits -- a consistent pace throughout -- are the most practical and effective target.
Why does my pace slow down in longer races?
Your pace naturally slows as distance increases because of glycogen depletion (muscles run low on stored carbohydrate), accumulated muscle fatigue, cardiovascular drift (heart rate creeps up even at a steady pace), and heat build-up. The Riegel formula captures this with its 1.06 fatigue exponent. On average, marathon pace is about 10-15% slower than 5K pace -- a runner with a 7:00/mi 5K pace might realistically average around 7:55-8:00/mi in a marathon.
How do I use a splits table during a race?
A splits table lists your target cumulative time at each kilometer or mile marker. Before the race, generate splits from your goal finish time and save them to your watch or write them on your arm. During the race, check your time at each marker: if you are more than 10-15 seconds ahead early, ease back; if you are behind, decide whether to push or adjust your goal. Splits keep you accountable and prevent starting too fast.
Is this running pace calculator free to use?
Yes. This running pace calculator is completely free, runs in your browser with no sign-up, and puts no limit on how many paces, times, splits, or race predictions you can calculate.
Can I switch between miles and kilometers?
Yes. Every result appears in both metric (min/km and km/h) and imperial (min/mi and mph) at the same time, so you can read splits and race predictions in whichever unit your watch or training plan uses.
Does a lower pace number mean I'm fitter?
A lower pace number does mean you are covering ground faster, but fitness is more than one figure. Sustainable pace is driven largely by your VO2 max -- the maximum rate at which your body uses oxygen -- plus your lactate threshold and running economy. Two runners with the same VO2 max can race different times depending on efficiency and pacing, so track pace alongside heart rate and perceived effort for the full picture.