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The basics: miles to kilometres and back again
The fundamental conversion every runner needs to know:
1 mile = 1.609 kilometres 1 kilometre = 0.621 miles
In practice, most runners round this to 1 mile being approximately 1.6 kilometres, which is accurate enough for almost every training and race situation.
The quick mental maths:
To convert miles to kilometres, multiply by 1.6. So 10 miles is approximately 16 kilometres. 6 miles is approximately 9.6 kilometres.
To convert kilometres to miles, multiply by 0.6 (or divide by 1.6). So 10 kilometres is approximately 6.2 miles. 21 kilometres is approximately 13 miles.
There is also a brilliant mathematical shortcut using Fibonacci numbers (the sequence 1, 1, 2, 3, 5, 8, 13, 21, 34...) that works surprisingly well for running distances. Consecutive Fibonacci numbers approximate the mile-to-kilometre ratio almost perfectly. So 5 miles is approximately 8 kilometres. 8 miles is approximately 13 kilometres. 13 miles is approximately 21 kilometres. For common race distances this is uncannily accurate, and it is far easier to remember in the middle of a long run than any formula.
Common race distances in miles and kilometres
5K in miles
A 5K is 3.1 miles (3.107 miles to be precise).
The 5K is the most popular race distance in the world and a brilliant starting point for new runners. Everything about it is accessible: the distance, the time commitment in training and on race day, and the sense of achievement when you cross the finish line. If you are building towards your first 5K, Runna's 5K training plan takes you from wherever you are right now to race-ready.
Average finish times: around 28 to 35 minutes for recreational runners, with beginners often finishing between 35 and 45 minutes.
10K in miles
A 10K is 6.2 miles (6.214 miles).
The 10K is exactly double the 5K distance and the natural next step for runners who have conquered the shorter distance and want more of a challenge without committing to half marathon training yet. If you are targeting a 10K, Runna's 10K training plan has you covered.
Average finish times: around 55 minutes to 1 hour 10 minutes for recreational runners.
Half marathon in miles and kilometres
A half marathon is 13.1 miles or 21.1 kilometres (21.0975 kilometres to be precise).
This is one of the distances runners most often need to convert because it is typically quoted in miles in the UK and US (the 13.1 appears on car stickers, race medals and training plans) but in kilometres much of the rest of the world. The number to remember is simply 13.1 miles or 21.1 kilometres.
The half marathon is the most rapidly growing race distance globally and one of the most rewarding distances to train for. It is long enough to require genuine preparation and short enough to be achievable for most runners with consistent training. Runna's half marathon plan ranges from 6 to 26 weeks depending on your starting point and goal.
Average finish times: around 2 hours to 2 hours 30 minutes for recreational runners.
Marathon in miles and kilometres
A marathon is 26.2 miles or 42.2 kilometres (42.195 kilometres to be precise).
The marathon is the iconic distance and the one most associated with running as a sport. The 26.2 figure is quoted so often in running culture that most runners already know it, but the kilometre equivalent of 42.2 (or more precisely 42.195) is worth knowing for when you are racing in Europe or following a plan in metric units.
If you are working towards a marathon, Runna's marathon training plan is personalised to your current fitness, your goal time and your schedule.
Average finish times: around 4 hours to 5 hours for recreational runners, with the global average sitting at 4 hours 22 minutes.
Ultramarathon common distances
Ultramarathons are any race longer than a marathon. The most common distances and their conversions are:
50K: 31.1 miles 50 miles: 80.5 kilometres 100K: 62.1 miles 100 miles: 160.9 kilometres
If you are eyeing an ultramarathon, Runna's ultramarathon training plan will get you there.
Converting pace: minutes per mile vs minutes per kilometre
This is where distance conversion gets most confusing for runners, and where the numbers diverge most dramatically. Pace per mile and pace per kilometre are completely different figures for the same running speed, and mixing them up can derail your training significantly.
Since 1 mile is 1.609 kilometres, your per-mile pace will always be a larger number than your per-kilometre pace. You cover more distance per mile, so it takes more time.
To convert from min/km to min/mile: multiply by 1.609. So a 5:00 min/km pace is approximately 8:03 min/mile.
To convert from min/mile to min/km: divide by 1.609 (or multiply by 0.621). So an 8:00 min/mile pace is approximately 4:58 min/km.
Runna's pace calculator does all of this for you instantly, which is the most reliable way to find your target pace for any race distance without doing mental arithmetic.
Why does it matter which unit your training plan uses?
A lot. And this is a mistake worth flagging clearly.
If your training plan says "easy run: 8 miles" and you run 8 kilometres instead, you have done roughly half the intended workout. If it says "tempo run at 5:00 pace" and you interpret that as 5:00 per mile rather than 5:00 per kilometre, you have just done a session at significantly higher intensity than planned.
Before starting any training plan, always check which unit it uses. Runna's plans are fully personalised and display in whichever unit you prefer, so this confusion does not arise. But for plans downloaded from other sources, it is worth double-checking before your first session.
The unit that causes most confusion is pace. Distance is relatively straightforward to check, but pace per mile versus pace per kilometre is easy to miss and the difference in actual running speed is significant.
Converting race times between distances
One useful thing runners often want to know is how their performance at one distance predicts their performance at another. The standard mathematical relationship used by coaches is that your pace typically slows by about 4 to 5% as distance doubles.
This means:
If you run a 5K in 25 minutes, you might expect a 10K in approximately 52 to 53 minutes. If you run a 10K in 50 minutes, a half marathon might be around 1 hour 50 minutes to 1 hour 55 minutes. If you run a half marathon in 2 hours, a marathon might be around 4 hours 10 minutes to 4 hours 20 minutes.
These are predictions, not guarantees. Your actual performance depends on training, conditions, pacing, nutrition and many other factors. But they are a useful starting point for setting race goals.
Runna's pace calculator can help you work out your target pace for any distance based on your current performance, which takes all the mental arithmetic out of goal setting.
The bottom line
Miles and kilometres. Two units, one sport, and endless potential for confusion if you are not sure which one you are working with.
The numbers worth memorising: 1 mile is 1.6 kilometres. A 5K is 3.1 miles. A 10K is 6.2 miles. A half marathon is 13.1 miles or 21.1 kilometres. A marathon is 26.2 miles or 42.2 kilometres.
For pace: your per-mile pace will always be a bigger number than your per-kilometre pace for the same speed, because a mile is longer than a kilometre. Multiply your km pace by 1.609 to get your mile pace. Divide your mile pace by 1.609 to get your km pace.
And for everything else, Runna's pace calculator is always there to do the maths for you.
Whether you are training for your first 5K or your tenth marathon, the distance is the same wherever in the world you run it. The unit is just the packaging.
