Running Pace Calculator
Calculate pace, finish time, or distance — plus race time predictions for 5K to marathon
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How Running Pace Works
Running pace is the time it takes to cover one unit of distance — one kilometer or one mile. A pace of 5:00/km means you run each kilometer in exactly five minutes. Understanding your pace is the foundation of structured training: it determines whether you’re running in your aerobic zone, at tempo effort, or at race speed.
This calculator works in three modes:
- Calculate Pace — enter distance and finish time, get pace per km and per mile
- Calculate Time — enter distance and target pace, get predicted finish time
- Calculate Distance — enter time and pace, get distance covered
It also uses the Riegel formula to predict your finish times across all standard race distances from 1 km to marathon.
How the Calculation Works
Pace Formula
Pace (sec/km) = Total Time (seconds) ÷ Distance (km)
To convert between per-km and per-mile pace: multiply by 1.60934 (km to mile) or divide by 1.60934 (mile to km).
To convert pace to speed: Speed (km/h) = 3600 ÷ Pace (sec/km)
Race Prediction: 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 at distance D2.
The exponent 1.06 reflects fatigue scaling — each doubling of distance takes slightly more than twice as long because runners slow down as distance increases.
A Worked Example
A runner completes a 5 km race in 22:30.
Pace: 22:30 ÷ 5 = 4:30/km (7:14/mile)
Speed: 3600 ÷ 270 = 13.3 km/h (8.3 mph)
Race time predictions:
- 10 km: 22:30 × (10/5)^1.06 = 22:30 × 2.085 = 46:55
- Half marathon: 22:30 × (21.1/5)^1.06 = 1:44:12
- Marathon: 22:30 × (42.2/5)^1.06 = 3:39:27
Pace Zones and Training
The Five Training Zones by Pace
Training by pace zones is most useful for experienced runners who know their race times. Beginners should train by heart rate or perceived effort until they have a reference race result.
Zone 1 — Easy / Recovery (65–75% of max HR)
About 60–90 seconds per km slower than 5K race pace. Conversational. Used for recovery runs and base building. Should make up 70–80% of total training volume.
Zone 2 — Aerobic Base (75–80% of max HR)
Comfortable but purposeful. You can speak in short sentences. Long runs belong here. This is where aerobic efficiency improves.
Zone 3 — Tempo / Threshold (80–88% of max HR)
Approximately 10K race pace. Comfortably hard — you can answer questions but can’t hold a conversation. Improves lactate threshold, the main determinant of distance running performance.
Zone 4 — Interval (88–95% of max HR)
Approximately 5K race pace to slightly faster. Used in structured interval sessions (e.g., 6 × 800m). Improves VO2 max and running economy.
Zone 5 — Repetition / Speed (95–100% of max HR)
Faster than 5K race pace. Short, fast reps with full recovery. Improves neuromuscular coordination and top-end speed.
Common Pace Benchmarks
| Goal | Pace Required | Notes |
|---|---|---|
| Sub-30 min 5K | Under 6:00/km (9:39/mi) | Achievable for many beginners within 6 months |
| Sub-25 min 5K | Under 5:00/km (8:03/mi) | Intermediate level |
| Sub-20 min 5K | Under 4:00/km (6:26/mi) | Advanced recreational |
| Sub-2 hour half | Under 5:41/km (9:09/mi) | Common recreational target |
| Sub-4 hour marathon | Under 5:41/km (9:09/mi) | Same pace, much harder |
| Sub-3 hour marathon | Under 4:16/km (6:52/mi) | Competitive amateur |
Key Assumptions and Limitations
The Riegel formula assumes consistent fitness across distances and becomes less accurate as the ratio between known and target distances increases. Predicting marathon time from a 1 km effort is unreliable; predicting from a half marathon is much more accurate. The formula does not account for course profile (elevation), weather conditions, or race-day factors. Pace per km and pace per mile conversions use exactly 1.60934 km per mile.
Frequently Asked Questions
How do I calculate my running pace?
Running pace is total time divided by distance. For a 5 km run in 25 minutes: 25 ÷ 5 = 5:00 per km. To convert to per mile, multiply by 1.609: 5:00 × 1.609 = 8:03 per mile. The calculator handles the math automatically in either direction — enter distance and time to get pace, or enter pace and distance to get finish time.
What is a good running pace?
It depends entirely on experience level. Beginner runners typically run 7–9 min/km (11–14 min/mile). Intermediate runners: 5–7 min/km (8–11 min/mile). Advanced recreational runners: 4–5 min/km (6:30–8 min/mile). Competitive club runners: 3:30–4:30/km (5:30–7 min/mile). Elite marathoners run around 2:50–3:10/km (4:30–5 min/mile). For reference, the world record marathon pace is approximately 2:53/km (4:35/mile).
How accurate are race time predictions?
The Riegel formula (T2 = T1 × (D2/D1)^1.06) is accurate within 5–10% for runners maintaining consistent training. It tends to underestimate marathon times for runners who don't have marathon-specific endurance training, and overestimate for well-trained ultramarathon runners. Predictions are most reliable when the known race distance is within 2× of the target distance — predicting a marathon from a 5K is less accurate than predicting it from a half marathon.
What is the difference between pace and speed?
Pace measures time per unit of distance (minutes per km or mile). Speed measures distance per unit of time (km/h or mph). They are reciprocals: a pace of 5:00/km equals a speed of 12 km/h (60 ÷ 5). Runners typically think in pace; cyclists and swimmers typically think in speed. Both are available in this calculator.
What pace do I need for a sub-4-hour marathon?
A sub-4:00 marathon requires covering 42.195 km in under 240 minutes — a pace of 5:41/km (9:09/mile) or faster. A common training target is 5:30/km (8:51/mile) to build in buffer for slower miles at the end. Your half marathon should be under 1:55–1:58 to suggest 4-hour marathon fitness.
How does the Riegel formula work?
The Riegel formula predicts race times across distances using the formula T2 = T1 × (D2/D1)^1.06. The exponent 1.06 reflects the fact that runners slow down as distance increases — performance degrades slightly more than linearly with distance. The formula was published by Pete Riegel in Runner's World in 1977 and remains the most widely used race prediction model despite its simplicity.