How do I calculate half marathon pace?

Divide your target by 21.0975. A two hour half is 7200 ÷ 21.0975 = 5:41 per kilometre, which is 9:09 per mile. Because the distance is not a round number the arithmetic is less friendly than at 5K or 10K, which is exactly why a calculator earns its keep here.

How long is a half marathon exactly?

21.0975 kilometres, or 13.109 miles — exactly half a marathon, which is itself 42.195 km by World Athletics definition. The familiar 13.1 is a rounding that loses about fifteen metres. After twenty-one whole kilometres you still have 97.5 metres to run, and after thirteen whole miles you have 176.

Do I need to take fuel during a half marathon?

For most people, yes. Common practice is that efforts beyond about ninety minutes benefit from thirty to sixty grams of carbohydrate an hour, and most half marathons take longer than that. Under about seventy-five minutes it is generally unnecessary. Tolerance varies considerably between individuals, so the useful step is practising your plan on long training runs rather than discovering how your stomach responds during the race.

When should I take my gels?

A feed roughly every thirty-five minutes after the first forty-five is the shape most plans use. For a two hour half that means around 45:00 and 1:20:00, which fall at about 7.9 km and 14.1 km — and it is the distance markers that are actually useful, since that is what you can see on the course. Taking one in the final ten minutes achieves nothing, as it will not be absorbed before you finish.

What pace is a sub-2 hour half marathon?

5:41 per kilometre, or 9:09 per mile, held for the whole 21.0975 km. Halfway comes at 1:00:00. Sub-1:45 needs 4:59 per kilometre and sub-1:30 needs 4:16. Those are averages, so a plan that starts marginally slower and finishes marginally faster still arrives at the same total.

How should I pace a half marathon?

Evenly, or very slightly negative, and more conservatively than you would a 10K. The distance is long enough that an over-ambitious first five kilometres is not something you recover from — it simply moves the difficulty to the closing miles and multiplies it. Most runners find the first three kilometres feel far too easy at correct pace, which is exactly how they should feel.

Can I double my half marathon time for a marathon?

No, and the gap is significant. Riegel's model puts a two hour half at about 4:10:12 for a marathon rather than a flat four hours — roughly ten minutes more. That is the running side alone; doubling the distance also roughly doubles the fuelling problem, and marathon performance depends on it far more heavily. Treat any marathon prediction from a half as an optimistic ceiling.

How much water should I drink during the race?

Enough to avoid getting thirsty, which for most people means a few mouthfuls at each station rather than a full cup. Most half marathons place stations roughly every five kilometres, so there are four on the course. In cool conditions many runners take very little; in heat, taking something at every station is sensible. Drinking to a fixed schedule regardless of conditions is a common and unhelpful habit.

How long does it take to train for a half marathon?

Around twelve to sixteen weeks from a base of regular running, and longer if you are starting from very little. The single most useful element is a weekly longer run built up gradually towards about eighteen kilometres — not the full distance, which is unnecessary and adds recovery cost without adding fitness. The rest of the week is better spent on comfortable running than on hard sessions.

Half Marathon Pace Calculator

Pick a half marathon target and this works out the pace you need, every split in kilometres or miles, and where your fuel should fall. A half marathon is 21.0975 kilometres — exactly half a marathon, and 13.109 miles rather than the 13.1 everyone quotes. That extra fraction matters more than it soun...

YOUR HALF MARATHON TARGET

TARGET TIME — h:mm:ss

COMMON TARGETS

YOU NEED TO HOLD

5:41 / km

PER MILE

9:09

SPEED

10.55 km/h

HALFWAY

1:00:00

A half marathon is 21.0975 km — 13.109 miles. That is 21 whole kilometres and a further 97.5 metres, worth 0:33 at this pace, so the last piece is neither a kilometre nor a mile.

SPLITS

1 km

1.00 km