Convert between pace, speed, distance and finish time. Calculate race splits, predict finish times for any distance and find your training pace zones.
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Pace, time & distance
Race predictor
Training zones
Running Pace Calculator
Pace - Finish Time - Distance
5K10KHalfMarathon
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5K10KHalfMarathon
km
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Split
Time at split
Lap time
Race Time Predictor
Training Pace Zones
Race predictions use the Riegel formula: T2 = T1 - (D2 - D1)^1.06. This assumes similar fitness and conditions. Predictions are less accurate at distances significantly longer or shorter than the known race.
The Guide
Understanding Running Pace
Pace is the time it takes you to cover one unit of distance, usually expressed as minutes per kilometre (min/km) or minutes per mile (min/mi). It's the most practical metric for runners because it directly tells you how fast you need to run to hit a target finish time.
Speed and pace are inversely related, the faster your pace, the lower the number (a 4:00/km pace is faster than 6:00/km). Speed in km/h = 60 - pace in min/km.
Common Race Pace Reference
Finish Time
Distance
Required Pace
Speed
25:00
5K
5:00 /km
12.0 km/h
30:00
5K
6:00 /km
10.0 km/h
45:00
10K
4:30 /km
13.3 km/h
1:00:00
10K
6:00 /km
10.0 km/h
1:45:00
Half
4:58 /km
12.1 km/h
2:00:00
Half
5:41 /km
10.6 km/h
3:30:00
Marathon
4:58 /km
12.1 km/h
4:00:00
Marathon
5:41 /km
10.6 km/h
Training Pace Zones
Not every run should be at race pace. Training in different pace zones develops different physiological adaptations. The majority of your running (around 80%) should be at an easy, conversational pace, this builds aerobic base and allows recovery. Only 20% should be at harder efforts.
Zone
% of 5K Pace
Feel
Purpose
Easy / Recovery
55-65%
Can hold a conversation
Aerobic base, recovery
Aerobic
65-75%
Comfortable but breathing harder
Endurance building
Tempo
80-90%
Comfortably hard, can speak a few words
Lactate threshold
Race Pace
95-100%
Hard, focused effort
Race simulation
VO2 Max / Intervals
105-115%
Very hard, 400m-1 mile repeats
Speed and VO2max
The Riegel Race Predictor Formula
The race predictor uses Peter Riegel's formula: T2 = T1 - (D2 - D1)^1.06. The exponent of 1.06 accounts for the fact that pace slows slightly as distance increases. This formula is most accurate when predicting distances within 2-4- of your known race distance. Predicting a marathon time from a 5K is possible but less reliable than predicting from a 10K or half marathon.
Frequently Asked Questions
For complete beginners, any pace where you can hold a conversation is appropriate, typically 7:00-9:00 min/km. The goal early on is to build time on your feet and aerobic base, not to run fast. Once you can run continuously for 30 minutes, you can start incorporating faster segments. Most beginners see their easy pace improve naturally within 8-12 weeks of consistent training.
The most common mistake in marathons is going out too fast. An even split (same pace throughout) or a slight negative split (second half slightly faster than first) produces the best results. Start 5-10 seconds per km slower than your target pace for the first 10km, then settle into race pace. The last 10km is when the race really starts, any time you bank early will be paid back with interest if you go out too fast.
The Riegel formula is most accurate when predicting between distances of similar length, for example, predicting a 10K from a 5K, or a marathon from a half marathon. Predictions become less accurate as the distance gap increases. Individual factors like training base, long run preparation (especially for marathons), and race conditions also affect real-world results. Use it as a target rather than a guarantee.
Use whichever unit your race is measured in. UK races typically use miles for shorter distances and km for longer events, though this varies. The important thing is consistency, pick one and stick with it for a training cycle so your pace perception is calibrated. Most GPS watches display both and you can switch at any time.
A negative split means running the second half of a race faster than the first. It's the optimal race strategy for most distances because it prevents early glycogen depletion and allows you to build into the race as you warm up. For a 10K, the ideal negative split is usually 5-10 seconds per km faster in the second half. For a marathon, even splits are more common at a recreational level, with a negative split being a sign of excellent pacing execution.
