Running Pace Calculator
Solve for pace, time or distance, get a full split table for your race, and see honest predictions for every standard distance from one performance.
Instant answers
Works offline once loaded
Nothing you type is sent anywhere
Pace, time or distance
Full split table
Race predictions
Enter any two — the third is calculated
Pace and splits follow this choice.
hoursminutesseconds
minutessecondsspeed
Finish time
—
Pace—
Speed—
Pace in the other unit—
Halfway point—
Estimated VO₂ max—
Calories burned (approx)—
Splits
| Km | Split | Elapsed | Remaining |
|---|
What this performance predicts at other distances
| Distance | Predicted time | Pace | Speed |
|---|
Riegel's formula with the standard 1.06 exponent. It is reliable between about half and double the distance you actually ran, and increasingly optimistic beyond that — a 5 K does not honestly predict a marathon unless you have trained for one.
Instructions
How to use this calculator
Step by step
- Pick what you want to solve for, then fill in the other two boxes. The field being calculated turns dashed and fills itself in — you never have to clear it.
- Choose kilometres or miles. Everything on the page follows that choice, including the split table, and the pace in the other unit is always shown so you can talk to runners who use either.
- Use the distance chips to jump straight to a standard race distance rather than typing 21.0975.
- Enter time as hours, minutes and seconds. Leave hours at zero for anything under an hour — the display drops it automatically.
- Pick a split strategy. Even splits are the default and the right answer for most races; the negative-split options ramp the pace so the second half is genuinely faster while the total still lands on your target time.
- Add your weight for a calorie estimate and your cadence for stride length. Both are optional and neither affects the pace arithmetic.
- Read the prediction table for what the same fitness should produce at other distances — and read the caveat under it before you enter a marathon on the strength of a 5 K.
Good to know
- Print the split table and write the elapsed column on your arm or a wristband. Trying to do this arithmetic at mile 20 is not realistic.
- Almost every recreational runner goes out too fast. If you are unsure, run the first mile 10–15 seconds slower than target pace and take it back later.
- Riegel predictions assume you have trained appropriately for the target distance. A 5 K time predicts a marathon only for someone who has done marathon mileage.
- Course profile is not in any of these numbers. A hilly race can cost several minutes over a half marathon compared with the same effort on the flat.
- Heat costs roughly two to three percent per five degrees over about fifteen Celsius. Adjust your target on the day rather than fighting the pace and blowing up.
- Cadence around 170–180 steps per minute is common among efficient runners, but it varies with height and speed. Chasing a number is less useful than avoiding a very slow, over-striding cadence.
The maths behind it
- Pace pace = time ÷ distance Seconds per kilometre or mile.
- Speed speed = distance ÷ time The reciprocal of pace, in km/h or mph.
- Riegel race prediction T₂ = T₁ × (D₂ / D₁)^1.06 The 1.06 exponent captures how pace decays with distance.
- VO₂ max (Daniels & Gilbert) VO₂ = −4.60 + 0.182258·v + 0.000104·v² v in metres per minute, divided by an intensity fraction that depends on duration.
- Running energy cost kcal ≈ 0.98 × kg × km Close to independent of pace — you burn about the same per kilometre fast or slow.
- Stride length step = speed (m/min) ÷ cadence (spm) A full stride is two steps.
- Unit conversion 1 mile = 1.609344 km Exact by definition.
What is a negative split and should I run one?
A negative split means the second half is faster than the first. Almost every distance world record and the vast majority of personal bests are run this way, because starting conservatively delays the point at which you accumulate fatigue. A 1–2% negative split is a good target; the split table here builds the ramp for you.
How accurate is the race prediction?
Riegel's formula is good within roughly half to double the distance you actually ran, provided you are trained for the target. Predicting a marathon from a 5 K reliably comes out several minutes optimistic, because the marathon is limited by fuelling and durability rather than the aerobic ceiling a 5 K measures.
Why does the calculator give different paces for km and miles?
They are the same speed expressed differently. A 5:00 per kilometre pace is 8:03 per mile, because a mile is 1.609 kilometres. The "pace in the other unit" row shows both so you never have to convert in your head.
Is the VO₂ max estimate reliable?
It is a good estimate from a genuinely all-out race effort lasting between about three and forty-five minutes. From a training run at conversational pace it means nothing — the formula assumes you finished at your limit. Laboratory measurement is the accurate method; this is the best you can get from a stopwatch.
Do I really burn the same calories running fast or slow?
Per kilometre, roughly yes — the cost of moving your body a given distance is dominated by your mass, not your speed. Per minute you obviously burn far more when running fast. The figure here is per distance, which is why it barely moves when you change the pace.
How should I adjust pace for hills?
A useful rule of thumb is about 12–15 seconds per mile slower for each 1% of uphill grade, and roughly 8 seconds per mile faster downhill — the gain never fully repays the loss. Run hills by effort and let the pace do what it does.
My GPS watch disagrees with the official race distance. Which is right?
The course. Certified courses are measured along the shortest legal route; GPS drift and the extra metres from weaving both add distance. Most runners record a marathon as 42.4–42.6 km. Your pace on the day was slightly faster than your watch said, not slower.