Calculate pace, finish time, or distance, then get Riegel race predictions, 7 training zones, and a full split table for any race.
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.
Research shows that elite runners do 80% of their training at easy conversational pace, slow enough to hold a full conversation. Most recreational runners do the opposite, running most sessions at a moderate-hard pace that's too hard to build aerobic base efficiently and too easy to build speed. The result is a plateau that proper easy-day pacing resolves within weeks. Your easy pace should feel almost embarrassingly slow, typically 2-4 minutes per mile slower than your race pace.
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.
| 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 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.
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.
Real-time pace feedback is the fastest way to learn proper training paces
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