Running pace calculator: splits, treadmill table and zones
Free running pace calculator: convert pace, time, km/h and m/s, predict 15 race distances, plan negative splits and place your pace in your lactate zones.
LactateThreshold now has a free running pace calculator at lactatethreshold.online/pace-rechner. Enter a distance and a time, a pace, or a speed, and the other values update at once: finish time, min/km, km/h, m/s and min/mile. The same page lists times for 15 distances, plans splits with an optional negative split, and has a treadmill table. If you have a lactate test, it also shows which training zone the pace falls into. No sign-up is needed.
Many pace calculators stop at conversion. This one was built for runners who already think in thresholds. The question it answers is not only "how fast is 5:00 per kilometre?" but "what does 5:00 per kilometre mean for me?"
Change one field and the rest follows
The input row has three fields: distance, time and pace. Distance accepts kilometres, "400 m" or "1 mi". Time accepts h:mm:ss or plain minutes. Pace can be entered in min/km (1:30 to 20:00), in km/h or in m/s. The unit selector applies everywhere on the page.
A slider below the inputs moves the pace between 6 and 24 km/h. That is the quickest way to see how much a small change does to a finish time.
The arithmetic behind it
The calculator does four conversions, and the page shows each of them so you can check the result by hand:
| Conversion | Formula | Example |
|---|---|---|
| Pace from time | time ÷ distance | 50 min ÷ 10 km = 5:00 min/km |
| km/h from pace | 60 ÷ pace in minutes | 60 ÷ 5 = 12 km/h |
| Pace from km/h | 60 ÷ km/h | 60 ÷ 12.5 = 4.8 min = 4:48 min/km |
| m/s from km/h | km/h ÷ 3.6 | 12 km/h = 3.33 m/s |
Why equal pace steps are not equal
Pace is speed turned upside down, so a smaller number is faster. That also means the same 20-second step changes speed by different amounts. Going from 6:00 to 5:40 min/km adds about 0.6 km/h. Going from 4:00 to 3:40 adds about 1.4 km/h. Faster runners need more speed for the same gain in pace. That is why the jump from 4:00 to 3:40 feels much harder than the jump from 6:00 to 5:40.
Sharing a plan
The current inputs are stored in the URL as d, t and p (distance, time, pace). Copy the address and you get a link that opens the calculator with exactly your numbers. You can send it to a training partner or keep it in a training log.
Times for every distance: same pace or Riegel prediction
The table below the inputs lists 15 distances in three groups: track and middle distance (400 m, 800 m, 1 km, 1500 m, 1 mile, 3 km), road (5 km, 10 km, 15 km, 10 miles, half marathon, 30 km, marathon) and ultra (50 km, 100 km).
A switch above the table selects one of two modes:
- Same pace: every distance at the pace you entered. This is useful for planning a training run, and it shows what holding one pace for longer would mean.
- Prediction (Riegel): the 1981 formula by Peter Riegel, T₂ = T₁ · (D₂/D₁)^1.06. Longer races are run slower, and the exponent of 1.06 builds that slowdown in.
The difference grows with distance. Here are both modes for a runner who has just run 10 km in 50:00:
| Distance | Same pace (5:00 min/km) | Riegel prediction | Predicted pace |
|---|---|---|---|
| 5 km | 25:00 | 23:58 | 4:47 min/km |
| 10 km | 50:00 | 50:00 | 5:00 min/km |
| Half marathon | 1:45:29 | 1:50:19 | 5:13 min/km |
| Marathon | about 3:31 | 3:50:00 | 5:27 min/km |
At the marathon distance the two answers differ by about 19 minutes. A runner who plans a marathon at 10 km pace is making a classic pacing mistake.
Where the prediction breaks down
The Riegel formula was derived from race records. It knows nothing about your glycogen stores or your weekly mileage. The page states its limits plainly: the prediction works best for efforts between about 3.5 minutes and just under four hours. For a marathon without dedicated long runs it is often too optimistic. If your long runs stop at 20 km, treat the marathon line as the fastest plausible time, not the target.
Splits, including a negative split
The splits table takes your distance and target time and breaks them into segments of 1 km, 400 m (one track lap) or 1 mile. Each row shows the segment, the distance mark, the segment time and the running total.
A second slider sets how the time is spread out: evenly, or with the second half up to 30 seconds per kilometre faster than the first. The finish time stays the same. Only the distribution changes, so the first kilometres get slower to pay for the faster finish. If the segment is too short for the distance (400 m laps for a marathon, for example), the page asks for a longer segment instead of printing a table nobody can use. A print button turns the table into a pace card.
Treadmill table: km/h to pace
Treadmills usually display km/h, while most training plans are written in min/km. The treadmill table covers 6 to 22 km/h in steps of 0.5 km/h. That makes 33 rows, each with pace, m/s and the resulting 5 km and 10 km times. The row closest to your current input is highlighted.
Under the table is a note on incline. Treadmill running has no air resistance, so the same speed takes slightly less energy than outdoors. The page cites a 1996 study by Jones and Doust in the Journal of Sports Sciences: a 1% grade came closest to the energy cost of outdoor running between roughly 10.5 and 18 km/h. Treadmill lactate tests are often run at 1% for the same reason. In December and January, when many runners move indoors for base training, this is the setting to check before comparing treadmill paces with summer runs outside.
Your pace inside your lactate thresholds
This section is what sets the calculator apart from a stopwatch tool. A pace only means something once you know where your thresholds are: 5:00 min/km can be an easy aerobic run for one runner and threshold work for another.
Without a lactate test: the example curve
Logged-out visitors see a schematic lactate curve for an example runner with LT2 at 4:20 min/km. A marker moves along the curve as you change the pace, and a label shows the zone and the pace as a percentage of LT2 speed. The example is labelled as an example. It shows how the placement works and is not meant as anyone's personal zones.
With your own test: your zones and finish times
Signed-in users who have saved a running test with LT2 see their own curve instead. The page draws it from LT1 and LT2 of the latest running test and shows the measured points. The pace is then placed in the same five zones the app uses (Recovery, Base 1, Base 2, Threshold, Peak), anchored at LT1, with the gap to LT2 in seconds per kilometre.
Below that, the calculator turns LT2 into race times using the app's rules of thumb: half marathon at 90 to 98% of LT2 speed, marathon at 84 to 92%. For the example runner with LT2 at 4:20 min/km (13.85 km/h), that gives:
| Race | Share of LT2 speed | Pace | Finish time |
|---|---|---|---|
| Half marathon | 90–98% | 4:48 to 4:25 min/km | 1:41:34 to 1:33:17 |
| Marathon | 84–92% | 5:09 to 4:42 min/km | 3:37:40 to 3:18:44 |
The ranges are wide on purpose. Where you land inside them depends on training history, long runs and race-day conditions, which a threshold alone does not capture. One useful check: compare these threshold-based times with the Riegel prediction from a recent race. If the race-based prediction is clearly slower than the threshold-based one, base endurance is the likelier gap. If it is faster, race sharpness or pacing are the places to look.
To get your own thresholds, the step test and the analysis are covered in Lactate threshold calculator: estimate LT1, LT2 and training zones. How the zones are built from the test is explained in Lactate training zones calculator: find your thresholds from test data.
Frequently asked questions
How do I calculate my running pace?
Divide time by distance. 50 minutes for 10 km gives 5 minutes per kilometre, a pace of 5:00 min/km. In the calculator, enter distance and time and the pace appears directly.
How do I convert km/h to min/km?
Divide 60 by the speed. 12 km/h gives 5:00 min/km, and 12.5 km/h gives 4.8 minutes, which is 4:48 min/km. The treadmill table lists every half step from 6 to 22 km/h.
How accurate is the race time prediction?
For trained runners and efforts between about 3.5 minutes and just under four hours, the Riegel formula is a reasonable starting point. For a marathon without long runs in training it tends to be too optimistic.
Which pace is my threshold pace?
A step test with lactate measurements shows it. LactateThreshold calculates LT1 and LT2 from your values. Once a running test is saved, the pace calculator places every pace you enter in your own zones automatically.
Does the pace calculator cost anything?
No. Conversion, distance table, splits and treadmill table are free and need no account. Placing the pace in your own zones requires a saved lactate test in your account.