Half Marathon Pace — Plan Your Race Strategy

How Pace Is Calculated

Pace is the amount of time it takes to cover a unit of distance, most commonly expressed as minutes per kilometer or minutes per mile. Speed is the inverse — the distance covered per unit of time, expressed in kilometers per hour or miles per hour. While speed is the standard for driving and cycling, most runners and walkers use pace because it gives a more intuitive sense of effort per unit of distance.

The relationship between pace and speed is mathematically straightforward: pace is the inverse of speed, and the conversion between metric and imperial units uses the standard factor of 1.60934 (the number of kilometers per mile). Understanding both pace and speed allows you to compare your performance across different measurement systems and training contexts.

The Formula

Worked Example

If you run 5 km in 28 minutes, your pace is 28 ÷ 5 = 5.6 min/km. Converting to minutes and seconds: 0.6 × 60 = 36 seconds, so your pace is 5:36 min/km. Your speed is 5 ÷ (28 ÷ 60) = 10.71 km/h. To convert to miles: pace per mile = 5.6 × 1.60934 = 9:00 min/mile, speed in mph = 10.71 ÷ 1.60934 = 6.66 mph.

FAQ-Style Explanations

Why do runners use pace instead of speed? Pace tells you how long a given distance will take — a 5 km run at 5:00 min/km will take exactly 25 minutes, which is more practical for race planning than knowing your speed in km/h. Speed is more useful for comparisons across different distances.

How does elevation affect pace? Uphill running demands more energy and slows pace by roughly 10–20 seconds per 100 meters of elevation gain. Downhill can slightly increase pace, but the compensation is not symmetrical — the time gained downhill rarely fully offsets the time lost uphill.

Does pace change with distance? Yes. Most runners can maintain a faster pace over shorter distances. Your 5 km race pace is typically 15–25 seconds per km faster than your marathon pace. This calculator gives the pace for a single distance — for longer events, expect some pace degradation.

Known Limitations

• The calculation assumes a perfectly flat, uniform surface. Real-world terrain, weather, and elevation changes will make actual pace vary significantly.
• Pace is a mathematical average, not a real-time measure. Most runners start slower and finish faster (or vice versa), and the average pace does not capture the effort distribution of the session.
• GPS-based pace can be inaccurate in tunnels, dense urban areas, or under heavy tree cover. For accurate pace measurement, use a calibrated foot pod or a measured course.