Running pace:
minutes per kilometre, speed and finish times

Pace is time per distance, speed is its inverse

Runners talk about pace, cyclists talk about speed. Both describe the same thing from opposite ends. Pace says how long a unit of distance takes, in minutes per kilometre. Speed says how much distance you cover in an hour. Races and training plans in most countries use pace, so the first skill is moving comfortably between the two.

The calculation is short but easy to botch because minutes and seconds are not decimals. 5:30 per kilometre is 5.5 minutes, not 5.3. Treat seconds as sixtieths of a minute and convert before you multiply.

Writing pace the way watches display it

Watches and race results display pace as minutes and seconds, such as 5:27 per kilometre. To use it in arithmetic, change it to decimal minutes: 27 seconds is 27 ÷ 60 = 0.45, so 5:27 is 5.45 minutes. Multiply that by the distance, and then convert the answer back.

The reverse conversion works the same way. If a plan gives you 5.8 minutes per kilometre, the 0.8 of a minute is 0.8 × 60 = 48 seconds, so the pace is 5:48. Stick to one representation in your head and convert only at the start and the end; that avoids the classic slip of treating 5:30 as 5.30.

A final tip for race day: write the target split for each 5 km on your wrist or phone. Doing division at kilometre 32 of a marathon is not a good use of oxygen.

The formulas

Reverse the first formula to plan a race. Finish time equals pace multiplied by distance, so a pace you can hold and a distance give you the clock time.

Worked example: 10 km in 50 minutes

Converting to miles is only necessary if the course or your watch uses them. Pick one unit and keep it for the whole race plan, so you are not doing arithmetic while tired.

Predicting one distance from another

A recent race over one distance gives a decent estimate for another. The commonly used rule scales time by distance raised to a power slightly above 1, because you slow a little as the distance grows. A 50-minute 10K points to roughly a 1:50 to 1:52 half marathon for a well-trained runner, not the 1:45 you would get by holding the same pace.

That gap is important when you set a goal. Holding 5:00 per kilometre for 21 km needs a level of endurance that many 10K runners have not trained for. A more cautious pace, a few seconds per kilometre slower than the 10K pace, is the one people can usually sustain.

Treat any prediction as a planning guide. Training volume, long runs, heat and course profile will push you either way, and a short tune-up race a few weeks out is a better predictor than any formula.

Pace chart for common targets

The half marathon column shows how small pace changes accumulate: 30 seconds a kilometre is over ten minutes across 21 km. That is why pacing is the central skill of longer races.

Building a race plan from a target time

1. 1Choose a realistic goal from recent training or a shorter race, not from hope.
2. 2Divide the goal time by the distance to get the average pace.
3. 3Decide whether to run even splits or to start slightly slower and finish faster.
4. 4Write down the time you should see at every 5 km, and check your watch against it.
5. 5Account for hills, heat and course turns, which make the average pace different from the flat-road target.

A negative split, where the second half is faster than the first, usually produces the best time for recreational runners, because starting hard wastes energy early. Even a two-minute gap in the half marathon is common and fine.

If you train with a heart rate monitor, effort zones give a second check on pace. A pace that feels sustainable but pushes your heart rate well above your usual long-run zone is a warning to ease off early in the race.

Why your watch and the course disagree

• GPS wanders: weaving around runners and cutting corners means a watch can show 10.1 km for a certified 10 km course.
• Certified courses are measured along the shortest legal path; if you run wider, you run further.
• Elapsed time includes stops at aid stations or traffic lights; moving time does not.
• Chip time starts when you cross the line, gun time when the race starts, and the difference can be a minute in a crowd.

Pacing a hilly course

A flat-pace plan breaks down on a course with climbs. Uphill kilometres cost you time and downhill ones return only part of it. A practical rule is to hold the effort rather than the pace: ease off on the climb, let the watch show a slower number, and recover time on the descent without sprinting.

When you set splits for a hilly route, add roughly 10 to 20 seconds per kilometre on a steady climb and take back some on the descent. The total finish time will be a little slower than the same effort on flat ground, and that is expected.

Training paces versus race pace

Most of your training is slower than race pace. Easy runs are at a conversational effort, often 1 to 2 minutes per kilometre slower than a 10K race pace for a beginner, with a smaller gap for experienced runners. Threshold and interval sessions are near or faster than race pace for short periods.

Use pace as a guide, not an order. Heat, hills, sleep and illness all change what a given effort looks like on the watch, and a coach or physician can help if you have a health condition that affects exercise.