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Half Marathon Pace Chart
This page prints a grid of finish times against distance checkpoints: four finish times across the top, six kilometre marks and six mile marks down the side, and the clock you should see at every crossing. It also works out the exact distance, the last 97.5 m, and how far a whole-second pace drifts.
Exact pace per kilometre for your target time
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1. Exact pace, then the pace a watch shows
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- Exact seconds per kilometre. Target seconds divided by 21.0975 km.
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- The same two paces are printed in minutes and seconds in the sentence above. Every one of the four values comes from the single target time you typed.
2. The last fraction, and where the rounding goes
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- The 22nd kilometre is short. Twenty-one whole kilometres end this far before the finish line.
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- The 14th mile is short by the same leftover distance, stated in metres.
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- Intermediate checkpoint clocks are rounded to the nearest whole second. The finish row is set to the exact target time, so the final stub takes the remaining fraction and the finish clock lands on your target.
3. The grid: finish times by checkpoints
Four finish times, one step apart, starting one step below the target you typed. The bold column is your target. Both kilometre and mile checkpoints are in this one table, so you never have to switch units to read either set.
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Change the target time or the step or read every formula on this page.
People reach this page looking for a half marathon mile pace chart, a half marathon time chart, a 1/2 marathon pace chart, or a half marathon pace chart in km. All four names point at the same grid: one table here holds both the kilometre checkpoints and the mile checkpoints, so there is no unit switch and no second chart to open.
Every formula used on this page
- Target time in seconds
- T = 3600 x hours + 60 x minutes + seconds. The whole page uses this one number; the three time fields feed nothing else.
- The distance in kilometres
- D_km = 42.195 / 2 = 21.0975 km. The marathon distance this site already uses is 42.195 km, so the half is exactly half of it.
- The distance in miles
- D_mi = 21.0975 / 1.609344 = 13.109378728... miles. One mile is 1.609344 km exactly. The page keeps this full value in the arithmetic and prints it rounded to nine decimal places.
- Exact pace per kilometre and per mile
- p_km = T / D_km seconds per kilometre; p_mi = T / D_mi seconds per mile. These are the two numbers in the first results block, before any rounding.
- The pace a watch shows
- w_km = round(p_km) and w_mi = round(p_mi), in whole seconds, printed as minutes and seconds. Both are shown next to the exact values so the difference is visible rather than hidden.
- Whole-second drift over the full distance
- drift_km = w_km x D_km - T, drift_mi = w_mi x D_mi - T. This is how far a constant whole-second pace misses the target. The two drifts differ because the two unit systems round at different places.
- A checkpoint clock
- clock(d) = round(T_i x d / D), where T_i is one of the four finish times in seconds, d is the checkpoint distance and D is D_km or D_mi to match that checkpoint's unit. For the finish row the page uses clock(D) = T_i exactly, with no rounding.
- The two leftover stubs
- km stub = (D_km - 21) x 1000 = 97.5 m. mile stub = (D_mi - 13) x 1609.344 = 176.028 m. Both describe the same short final piece of the course, measured from the last whole kilometre and the last whole mile.
- The four finish times
- T_i = T + (i - 1) x 60 x step, for i = 0, 1, 2, 3. With the default 1:45:00 target and a 5 minute step these are 1:40:00, 1:45:00, 1:50:00 and 1:55:00. A time that rounds to zero or below is not printed.
Three worked examples
Every row below is recomputed on load by the same function that drives the grid above, from the target time printed beside it. Nothing is typed in by hand.
What this page deliberately does not do
- No prediction. You supply the target; this page does not read a recent race or tell you what you can run.
- No negative splits and no even-versus-negative toggle. Every cell is an even split.
- No age or sex grading, no sex selector, and no invented factor table.
- No elevation, hill, weather, heat, humidity or wind correction.
- No training plan, session prescription, weekly volume, coaching or medical advice.
- No good-or-bad label, no cut-point and no grade for any finish time.
- No printable pace band, no course presets, no aid-station markers and no watch or GPS sync.
- No other distance. The half marathon is the one distance on this page.
Every number above is worked out from the four entries you type, in this browser, when you type them. Nothing is uploaded, nothing is saved, and every formula is printed with its arithmetic on this page.
Questions
What is a half marathon pace chart?
It is a table: each column is one finish time, each row is one distance mark, and each cell is the clock you should see as you pass that mark. This page prints four finish times and twelve checkpoints, six in kilometres and six in miles, all worked out from the one target time you type. A single-target strip is a different thing; the half marathon split calculator on this site prints one of those, and this page does not.
How long is a half marathon, exactly?
The marathon distance used across this site is 42.195 km, so the half is 21.0975 km. One mile is 1.609344 km exactly, so the same distance is 21.0975 / 1.609344 = 13.109378728 miles. Both constants, and the division that connects them, are printed in the formulas section so you can redo them with a calculator.
What happens in the last 97.5 metres?
Twenty-one whole kilometres end 97.5 m short of the finish, and thirteen whole miles end 176.028 m short. Those two leftover stubs are printed in the second results block. Every intermediate checkpoint clock is rounded to the nearest whole second; the finish row is set to the exact target time instead, so the last stub absorbs whatever fraction of a second the rounding left over and the finish clock lands exactly on the time you asked for.
Why is the whole-second pace slightly off?
A watch shows a pace in whole seconds. For a 1:45:00 target the exact pace is 298.613580 seconds per kilometre, which a watch prints as 4:59 (299 s). Holding 299 s/km for the full 21.0975 km takes 8.15 seconds longer than the target. The mile version is 480.571973 s/mile printed as 8:01, which runs 5.61 seconds long. Both gaps are worked out from the same inputs and shown in the results, and this page never rounds the finish clock.
Does this page predict my finish time?
No. You bring a target time you already have in mind, and the page works out what that time costs at every checkpoint. It does not read a recent race, it does not tell you what you are capable of, and it gives no training advice. The race time predictor on the home page is the page that goes in the other direction.
Can I get a printable pace band or a negative split here?
No. This is a screen reference grid with even splits only. It prints no wearable band, offers no even-versus-negative toggle, and does not model how much slower an early section should be. It also has no elevation, weather, age or sex adjustment, no course or aid-station list, no watch or GPS sync, and no good-or-bad label for any time.
What does this page deliberately not do?
It does not predict a finish time, grade by age or sex, correct for hills or weather, plan training, offer medical advice, print a pace band, model negative splits, sync to a device, or handle any distance other than the half marathon. It has no account, no upload and no saved data. Every number is worked out locally from the four fields you fill in, and every formula is printed on the page.