Race Pace Calculator

What this page does

A race pace calculator works out the pace side of a race: what pace a finish time costs, what time a pace costs, and how far a pace gets you. Three quantities are in play — distance, finish time and pace — and any two of them fix the third exactly. That is the whole tool, and it runs in every direction: give it a pace and a distance and it returns a finish time; give it a finish time and a distance and it returns the pace; give it a pace and a finish time and it returns the distance, which is the direction no other page on this site offers at all.

No other page on HealthCalcPlus takes a pace as an input. The race time predictor on the home page takes a race result and predicts a finish time for a different distance. The 5K pace calculator takes a 5K finish time with the distance fixed at 5 km. The running split calculator takes a target time and a distance. The marathon pace band takes a target marathon time. Every one of those starts from a time you have already decided on; this page starts from whichever two numbers you actually have, and one of the three can be a pace on its own.

Everything runs in your browser. Nothing you type is sent to a server, there is no account and no upload, and the numbers you type never leave the page. The three quantities are always shown together in the stats row above, so the answer to one question carries the other units with it: a pace per kilometre next to the same pace per mile, and a speed in km/h next to the same speed in mph.

How the numbers are calculated

There is no model here and nothing to tune: four divisions and their inverses, in two unit systems. With D the race distance in metres and T the finish time in seconds:

p_km = T ÷ (D ÷ 1000)    p_mi = T ÷ (D ÷ 1609.344)    v_km/h = (D ÷ 1000) ÷ (T ÷ 3600)    v_mph = (D ÷ 1609.344) ÷ (T ÷ 3600)

and the same four run backwards, from the pace in whichever unit you typed it in:

T = p × (D ÷ 1000)    T = p × (D ÷ 1609.344)    D = (T ÷ p) × 1000    D = (T ÷ p) × 1609.344

• D — the race distance in metres. Typed in kilometres or miles and converted once, at the point of entry. 100 m to 100 miles.
• T — the finish time in seconds. 1:00 to 47:59:59.
• p — the pace in seconds per kilometre or per mile, in whichever unit you selected. 2:00 to 30:00 per unit.
• p_km — the same pace expressed in seconds per kilometre, always shown even when you typed miles.
• p_mi — the same pace expressed in seconds per mile, always shown even when you typed kilometres.
• v_km/h — average speed. Kilometres run divided by hours taken, so it is (D ÷ 1000) ÷ (T ÷ 3600).
• v_mph — the same speed in miles per hour, using D ÷ 1609.344 instead.

The only numbers that are not derived from your own input are unit definitions, and every one of them is exact: 1 km = 1000 m; 1 hour = 3600 s; and the international mile = 1609.344 m exactly, fixed by the 1959 international yard and pound agreement — a definition, not a measurement, and not a convention any running site is free to change. There is no borrowed pace table, no age-grading factor, no weather model and no external data file anywhere on this page. Nothing here is transcribed from anywhere, so there is no baseline to mark as a baseline.

A worked example: half marathon at 4:30 per kilometre

The example the page opens on. D = 21.0975 km = 21097.5 m, and p = 4:30 = 270 s per kilometre:

• Finish time — 270 × 21.0975 = 5696.325 s, printed 1:34:56. The exact value ends in a third of a second; the page rounds once, at the end, and never mid-chain.
• Pace per mile — 270 × 1609.344 ÷ 1000 = 434.52288 s, printed 7:15.
• Speed — 21.0975 ÷ (5696.325 ÷ 3600) = 13.33 km/h, which is 8.28 mph.
• Halfway — 5696.325 ÷ 2 = 2848.1625 s, printed 47:28.
• The 21 km mark — 21 × 270 = 5670 s = 1:34:30, and the last 97.5 m add 26.325 s, which is why the finish row reads 1:34:56 rather than a whole number of minutes.

Change one number and the whole page moves with it: the stats, the splits, the grid highlight and the band are all rebuilt from the same four divisions, in the order you type them.

Two checks you can run on the numbers yourself

• The grid has to agree with the tool. The grid row for 4:30 per kilometre says a half marathon is 1:34:56 — the same number the tool returns for the same input, because the grid is the same arithmetic applied to four fixed distances. If the two ever disagreed, the grid would be the thing to distrust.
• Other pages on this site publish the same division. The 5K pace calculator publishes 5 km in 20:00 as 4:00 per kilometre, 6:26 per mile and 15.00 km/h; type 5 km and 20:00 into this page and the stats row returns exactly those four numbers. The running split calculator publishes 1:45:00 for the half marathon as 298.613580 s per kilometre; entering 21.0975 km and 1:45:00 here returns 4:59 per kilometre, which is that number rounded to the nearest second. Two pages, one division, and the numbers agree.

The race pace grid, and why it is a grid

The grid above holds 25 rows: every pace from 3:00 to 9:00 per kilometre in fifteen-second steps, and the finish time each one buys at 5K, 10K, the half marathon and the marathon. The row nearest the pace you are looking at is highlighted, so the grid doubles as a way of reading the page at a glance.

It exists as a grid rather than another calculator because the question it answers is the one you have before you have picked a target: what does a 4:30 kilometre actually buy me? A calculator answers that only once you already know the time you are asking about; a grid shows you the number and its neighbours at the same time, which is also how you find out that 4:30 and 4:45 per kilometre are a six-minute marathon apart.

Three notes on reading it. The rows are per-kilometre because that is the unit most pace charts are printed in — the stats row above gives the per-mile equivalent of whatever you are looking at, so nobody has to convert by hand. The finish times are computed from the exact pace, not from the rounded fifteen-second step, so the columns add up instead of drifting. And the grid covers 3:00 to 9:00 per kilometre, which is 15:00 to 45:00 for a 5K, 30:00 to 1:30:00 for a 10K, 1:03:18 to 3:09:53 for the half marathon and 2:06:35 to 6:19:45 for a marathon; a pace outside that window still works in the tool, it just has no row to highlight.

The splits, and the band you can wear

The split table is the same arithmetic one marker at a time: at a constant pace the clock at each whole kilometre or mile is the pace multiplied by the number of markers so far, and the finish row is the target itself. Which marker to use is a choice, not a fixed setting — a 5K wants whole kilometres, a mile race wants whole miles, and an ultra wants 5 km or 5 miles because a band with 80 rows is not a band. The table is capped at 60 rows, the same cap the running split calculator uses, and the page refuses rather than printing an unusable strip.

The band is the same rows collapsed onto a strip of paper. It is drawn 170 mm wide with a 50 mm scale check near the top: print it, hold a ruler against that line, and if it measures 50 mm the band came out the size it was drawn — print dialogs default to "fit to page", which quietly rescales it. Cut along the border, fold down the middle, and tape the ends around your wrist.

Every printed time is rounded to the nearest second, so no row is more than half a second away from the exact clock, and the finish row prints the target exactly. If you have no printer, Download band writes the same rows to a plain-text file and Copy band puts them on your clipboard; neither is a substitute for the printed strip, but the text file reprints identically whenever you want it.

Supported range and limits

• Distance: 100 metres to 100 miles (100 m to 160.9344 km), entered in kilometres or miles with as many decimals as you like. In this direction it is an output, not an input, when you solve for distance.
• Finish time: one minute to 47:59:59, entered as hours, minutes and seconds, with minutes and seconds between 0 and 59. Times outside that window are refused rather than silently clamped.
• Pace: 2:00 to 30:00 per kilometre or per mile, entered as minutes and seconds. At the kilometre end that is 30.00 km/h down to 2.00 km/h; at the mile end it is 48.28 km/h down to 3.22 km/h.
• Markers: whole kilometres, whole miles, every 5 km or every 5 miles. At most 60 rows in the split table and the band: 100 miles is 101 rows at 1 mile, 33 at 5 km and 21 at 5 miles, and the page tells you to widen the interval rather than printing a strip you cannot wear.
• Rounding: times to the nearest second, distances to four decimal places, speeds to two decimals. One rounding, at the end, never halfway through a chain of calculations.
• Grid: 3:00 to 9:00 per kilometre in fifteen-second steps, 25 rows. A pace outside that window still builds the splits and the band; only the highlighted row is absent, and the page says so.
• Cost: none. No account, no email, no paywall, no daily limit, no request to a server.
• Privacy: every number is computed in your browser. Nothing you type is sent anywhere or stored — reload the page and it is gone.
• Works offline once the page has loaded, and on a phone.

What this page deliberately does not do

• No prediction. This page does not tell you what you are capable of. It takes the numbers you give it and converts between them; telling you what a 10K says about your marathon is the race time predictor on the home page, which moves one recent result along the distance curve, and the race time calculator, which prices a course on top of it.
• No hill adjustment. Every split here is an even split on a flat course: one pace, repeated. A hilly race needs a per-kilometre elevation profile and a published energy-cost model, which the marathon split calculator and the race time calculator do on this site. This page does not borrow their model, because a band that quietly mixes two models is worse than one that states a single one.
• No second clock. Every row carries one clock, the one you keep. If your race is chip-timed and you want to know what the gun clock above the markers reads, the splits calculator carries both side by side with a start-line-gap estimate.
• No negative splits. A band carries one target and one number per row; a negative split is a shape, not a target, and printing one needs a model of how much slower the first half should be. That would be a guess about you, so the page prints even splits and leaves the shape to you.
• No aid stations and no course presets. Both need one race's own layout, and courses are re-measured. There is no "Boston" option and no water-stop column.
• No age grading and no weather correction. Both need published tables or models this page does not have. Rather than ship a made-up coefficient, it leaves them out and prints the numbers it can defend.
• No treadmill mode. A treadmill pace is a different question — belt speed, incline and the calibration of the machine all sit between the setting and the effort — and this page has no source it can stand behind for any of them.
• No fixed-distance extras. No 400 m lap table, no lane arithmetic, no mile-only tables: those live on the 5K pace calculator, the track split calculator and the mile splits calculator, each of which fixes something so it can print something else. This page keeps the distance variable, and spends that freedom on the three-way conversion instead.

Questions

What is a race pace calculator?

It converts between the three quantities of a race — distance, finish time and pace — in whichever direction you have the numbers. Give it any two and it returns the third, plus the pace in both units and the speed in km/h and mph. This one also prints the splits, a 25-row race pace grid for 5K, 10K, half marathon and marathon, and a band you can cut out and wear.

What pace do I need for a half marathon in 1:45:00?

4:59 per kilometre, which is 298.613580 seconds, and 8:01 per mile — 12.06 km/h, or 7.49 mph. The 5 km mark falls at 24:53, the same number the running split calculator publishes for this target, because it is the identical division. Type 21.0975 km and 1:45:00 into the tool above and the stats row shows all four figures.

Can I work out my pace from a finish time?

Yes — that is the second mode. Pick "Finish time + distance to pace", enter the distance and the time, and the page returns the pace per kilometre and per mile along with the speed. It is the calculation most race reports skip: a finishing time alone does not tell you whether the race was run evenly, and a pace does.

How far will I get at 8:00 per mile in 90 minutes?

11.25 miles, which is 18.1051 km, at 7.50 mph (12.07 km/h). That is the third mode, and it is the one no other page on this site offers: two quantities that are not distance, and the distance comes out. It is the arithmetic behind "do I have time for one more loop", and behind a race whose distance is not on any list.

Why does the page show pace per kilometre and per mile together?

Because the two are one conversion apart and only one of them is the one you think in. A pace per kilometre times 1.609344 is the pace per mile, so showing both costs nothing and saves the reader a conversion at the exact moment they are trying to read a watch. The same goes for the speed pair: km/h and mph are the same speed, and a course measured in kilometres can still be run by someone whose watch is set to miles.

Is the race pace grid a prediction?

No. It is the same division this page performs on your own input, applied to four fixed distances: pace multiplied by 5 km, by 10 km, by 21.0975 km and by 42.195 km. It contains no model of fitness, no age grading and no comparison with other runners, and it will happily print a marathon time that no human has ever run. Predicting a finish time from a race you have already run is the home page's job.

Does this work for a hilly course or a treadmill?

No, and the page says so in its own limits section. The arithmetic is even splits on a flat course: one pace, repeated. A hilly course needs a per-kilometre elevation profile and a published energy-cost model, which the marathon split calculator and the race time calculator do here. A treadmill is a different question again — belt speed, incline and machine calibration all sit between the setting and the effort — and this page has no source it can stand behind for any of them.

Can I print the band?

Yes. Print band opens the print dialog with only the band on the page, drawn at 170 mm with a 50 mm scale check so you can confirm the printer kept it at 100%. If you have no printer, Download band writes the same rows to a plain-text file and Copy band puts them on your clipboard.