OnSumoTools

Running Pace Calculator

Calculate running pace, finish time, or distance. Generate split tables for 5K, 10K, half marathon, and marathon planning.

Run setup

Distance unit
Finish time (h : m : s)
Pace (m : s per km)

Pace

5:00 / km

Also 8:03 / mi · 12.00 km/h

Split table

SplitAtLapCumulative
11 km5:005:00
22 km5:0010:00
33 km5:0015:00
44 km5:0020:00
55 km5:0025:00

Riegel race projections

  • 10K52:07
  • Half marathon1:55:00
  • Marathon3:59:47

Race projections use the Riegel formula. Real courses, weather, and pacing change finish times.

How does the Pace Calculator work step by step?

The calculator converts all inputs to seconds before any arithmetic, then reformats results to mm:ss (pace) or hh:mm:ss (finish time) for display. In Pace mode, pace = total elapsed time (seconds) ÷ distance. In Finish Time mode, finish time = pace (seconds per unit) × distance. In Split Calculator mode, the same formula runs for each segment, and segment times accumulate to a cumulative total. Unit conversion uses the exact factor 1 mile = 1.60934 km; switching units rescales pace proportionally. Key assumption: the calculation assumes a perfectly even effort — pace does not vary across the distance. Edge case: treadmill distances are often quoted in miles even in metric countries; if you mix km and miles the pace result will be off by a factor of 1.609, so confirm your distance unit before entering. For races with elevation, the flat-equivalent pace will understate actual effort.

What does a typical Pace Calculator result look like?

Goal: Run a marathon (42.195 km) in 3:30:00 ` Pace needed = 3:30:00 / 42.195 km Total seconds = 3 x 3600 + 30 x 60 = 12,600 sec Pace = 12,600 / 42.195 = 298.6 sec/km = 4:58.6/km (approximately 4:59/km) ` In miles: 4:59/km x 1.60934 = 8:01/mile

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Frequently asked questions

  • What is running pace?

    Pace is the time it takes to cover one unit of distance, expressed as minutes and seconds per kilometer or per mile. A pace of 5:00/km means you complete each kilometer in exactly five minutes. Pace is the inverse of speed: lower numbers mean faster running, which is the opposite of what many people expect when they first encounter the metric.

  • What is the Riegel formula?

    Pete Riegel published a formula in 1977 for predicting race performance at different distances based on a known result: T2 = T1 x (D2/D1)^1.06. The exponent 1.06 was derived empirically from race data and reflects the non-linear way fatigue accumulates over distance. The formula works best for aerobically trained runners and distances in the 1-100 mile range.

  • How accurate are Riegel projections for the marathon?

    Riegel projections are most accurate when the runner has trained specifically for both distances. A 5K-trained runner projecting to marathon has typically not built the aerobic base and long-run capacity that marathon performance requires, the projection assumes comparable fitness across the aerobic spectrum. Treat it as a ceiling estimate, not a guaranteed result without marathon-specific preparation.

  • What is a negative split strategy?

    A negative split means running the second half of a race faster than the first. Race data shows that negative splits or even pacing produce faster finish times than positive splits (starting fast and slowing) for most distance runners. The split table shows even splits; adjust your target pacing strategy based on course profile, weather, and your own experience.

  • Can I use this for cycling or rowing?

    The pace formulas are distance-and-time agnostic and will work for any activity measured in distance per unit time. The Riegel formula and pace zone descriptions are calibrated for running; do not apply them directly to other sports without adjusting for the different physiological demands.

  • What does average speed mean in relation to pace?

    Speed is distance divided by time, expressed in km/h or mph. Pace is time divided by distance, expressed in min/km or min/mile. They describe the same movement from inverse perspectives. A pace of 5:00/km corresponds to a speed of 12 km/h. The tool displays both.

Pace, time and distance: pick two

Running comes down to three numbers. How far, how long, how fast. Give the calculator any two and it solves the third. Want to know what pace gets you a 50-minute 10K? Enter the distance and time. Know your pace and want a finish time for a half marathon? Enter pace and distance.

Race presets for 5K, 10K, half marathon and marathon save you typing.

Pace and speed

Pace is time per distance, like 5:30 per kilometre or 8:50 per mile. Speed is distance per time, like 11 km/h. They're two ways to say the same thing. Runners think in pace. Cyclists think in speed. The calculator shows both, in kilometres or miles, so you can switch freely.

It works for other sports too. Rowing, walking and swimming all use time over distance. Just remember that swim pace is usually per 100 metres, so enter distances to match.

Splits

A split is your time at each kilometre or mile marker. The tool lists them for your target pace. Print them or write them on your wrist, and check against them mid-race. It's easier to stay on track one split at a time.

A negative split means running the second half faster than the first. It's a smart race plan for many runners, since starting too fast is the most common way to blow up late.

Riegel projections

Peter Riegel's formula predicts a time at a new distance based on one you've run. Feed it a 10K result and it projects a half marathon or marathon. The idea is that pace slows by a predictable amount as distance grows.

It works best between nearby distances. A 5K to a 10K projection is more trustworthy than a 5K to a marathon one. The marathon is where the formula tends to be too hopeful, because it assumes you've trained for the longer distance. Without the long runs in your legs, expect to be slower.

Using it in training

Easy runs should feel conversational, noticeably slower than race pace. Many runners go too hard on easy days and too soft on hard ones. Use the calculator to set race pace, then plan easy runs well beyond it.

Be realistic with goal times. A jump of a minute per kilometre is huge. Aim for gains of a few seconds per km over a training block.

All the math happens in your browser.