Calculate pace, finish time, or distance — then get Riegel race predictions, 7 training zones, and a full split table for any race.
Unit system
hrs
min
sec
Unit system
min
sec
Unit system
hrs
min
sec
min
sec
Uses the Riegel formula (T² = T¹ × (D²/D¹)1.06) — the gold standard for race time prediction, accurate to within 2–3% for most runners.
hrs
min
sec
Unit system
min
sec
How Pace Is Calculated
Running pace is simply total time divided by distance: Pace = Time ÷ Distance. Run 5 miles in 40 minutes and your pace is 8:00 per mile. The calculator works in both directions — give it any two of the three variables (pace, time, distance) and it solves for the third. All inputs use hours, minutes, and seconds to avoid rounding errors from decimal time.
Converting between miles and kilometers: 1 mile = 1.60934 km. A 8:00/mile pace equals 4:58/km. A 5:00/km pace equals 8:03/mile. Speed (mph or km/h) is the inverse: speed = 60 ÷ pace in minutes. An 8:00/mile pace = 60/8 = 7.5 mph.
Pace Reference Table
min/mile
min/km
mph
km/h
5K
Half
Marathon
6:00
3:44
10.0
16.1
18:39
1:18:29
2:37:11
7:00
4:21
8.6
13.8
21:45
1:31:34
3:03:21
8:00
4:58
7.5
12.1
24:51
1:44:38
3:29:21
9:00
5:35
6.7
10.7
27:57
1:57:43
3:55:22
10:00
6:13
6.0
9.7
31:04
2:10:48
4:22:22
11:00
6:50
5.5
8.8
34:10
2:23:52
4:48:23
12:00
7:27
5.0
8.0
37:17
2:36:57
5:14:24
13:00
8:04
4.6
7.4
40:23
2:50:02
5:40:24
15:00
9:19
4.0
6.4
46:35
3:16:11
6:32:25
The Riegel Race Prediction Formula
The Race Predictor uses the Riegel formula: T² = T¹ × (D²/D¹)1.06, where T¹ is your known race time at distance D¹, and T² is the predicted time for distance D². The exponent 1.06 captures the physiological reality that longer races require a slower pace — you slow down more than linearly as distance increases. It is accurate to within 2–3% for most trained runners and is used by coaches worldwide for race planning.
Training Zones Explained
The 7 training zones shown after every calculation are derived from your current pace and represent distinct physiological effort levels. Recovery (130% of race pace) and Easy (120%) build aerobic base and promote recovery — most elite runners do 70–80% of training here. Aerobic (112%) and Tempo (105%) improve lactate threshold and running economy. Threshold is race pace. Interval (95%) and Repetition (88%) develop VO&sub2;max and speed. Using all seven zones in a balanced training plan is more effective than running the same pace every day.
Frequently Asked Questions
What is a good running pace?
It depends entirely on the runner and distance. The average recreational runner finishes a 5K in 28–35 minutes (9:00–11:15/mile). A "good" marathon for a recreational runner is under 4:30 (~10:18/mile). Sub-3:00 marathons (~6:52/mile) represent serious competitive fitness. For beginners, completing any distance is a good pace. Track your own improvement over time rather than comparing to others.
How do I convert pace to speed (mph or km/h)?
Speed (mph) = 60 ÷ pace in decimal minutes. An 8:00/mile pace = 60 ÷ 8.0 = 7.5 mph. For km/h: speed = 60 ÷ pace_in_min_per_km. A 5:00/km pace = 60 ÷ 5 = 12 km/h. This calculator shows both speed conversions automatically in the stat cards after every calculation.
How accurate is the Riegel race predictor?
Within 2–4% for most trained runners predicting similar distances (e.g., 10K → half marathon). Accuracy drops when predicting much longer races from short efforts — a 5K to marathon prediction can be off by 5–10% because the physiological demands are very different. Training specificity matters: if you've been doing long runs, your marathon prediction from a 5K will be more accurate. Use it as a goal range, not a guaranteed finish time.
What is a negative split strategy?
Running the second half of a race faster than the first. Most world records and PR performances use negative splits or even pacing. Starting slightly slower than goal pace conserves glycogen, prevents early lactate accumulation, and leaves energy for a strong finish. A 1–3% faster second half is the sweet spot for most distances. The splits table in this calculator shows even-pace splits — aim to hit those in the first half and run slightly faster in the second.
Should I use min/mile or min/km?
Use whatever your watch, race, and training environment uses. In the US, most runners use min/mile. In most of the rest of the world, min/km is standard. Mathematically they're identical — this calculator handles both and shows the conversion automatically. If you're following a training plan written in one unit while racing in another, the pace conversion in the stat cards makes it easy to translate.
How do I calculate my pace from a GPS watch?
Most GPS watches show pace in real time. For manual calculation: note your finish time in total seconds, divide by distance in your chosen unit. 5 miles in 42:30 = 2550 seconds ÷ 5 = 510 seconds/mile = 8:30/mile. This calculator does this automatically — just enter distance and time in the Find Pace tab.