Pace
calculator

Enter a distance and a target time; get your pace, speed, and even splits in min/mi or min/km. With the reason one pace can't be carried across race distances.

How the math works

Pace is one identity: time divided by distance. Enter two of pace, time, and distance and the third follows.

The distance presets use World Athletics standard course lengths: a 5K is 3.106856 mi, a half marathon is 21.0975 km (13.109375 mi), and a marathon is 42.195 km (26.218750 mi). Unit conversions are exact, per NIST SP 811 — no rounded factors.

Worked example

A runner with a 5K personal best of 22:00 wants to target a sub-20:00. What pace does each require, and how much faster is that?

• Target pace (20:00 for 5K): 20:00 ÷ 3.107 mi = 6:26/mi (4:00/km)
• Current pace (22:00 for 5K): 22:00 ÷ 3.107 mi = 7:05/mi (4:24/km)
• Improvement required: 39 sec/mi (24 sec/km)
• Even splits at goal pace (per km): 4:00, 8:00, 12:00, 16:00, 20:00

When this calculator is wrong

The pace this prints is a race target, and the most common way to misuse it is to run most of your training at it. Polarised-training research (Seiler 2010 and subsequent) points to roughly 80% of endurance running in easy Zone 1–2 — well below goal pace — and about 20% hard, with very little in the moderate "grey zone" that goal-pace running tends to sit in. The grey zone feels productive but drives aerobic adaptation less than easy work and VO2 max less than hard intervals. The exception is time-crunched athletes with fewer than four sessions a week, for whom some grey-zone running is unavoidable and probably fine.

• Even splits are an assumption, not a plan. The table above divides the effort evenly. Real races reward even-to-slightly-negative splitting; going out faster than goal pace and banking time almost always costs more in the back half than it saves up front.
• It is not a cross-distance predictor. Pace slows as distance grows. The men's 5K world-record pace is 4:03/mi (2:31/km); the men's marathon record pace is 4:36/mi (2:51/km) — about 33 sec/mi (20 sec/km) slower, even at the elite ceiling. Carrying your 5K pace to a marathon overshoots badly. Predicting a time at a new distance is a different formula (Riegel).
• GPS pace lags reality. Watch pace drifts on turns, in tunnels, and among tall buildings. For pacing a race, trust marked mile or kilometre splits over the instant-pace readout.

What to do with the result

Set the goal pace from a recent race or a time trial, not from what you hope to run. Then use the split column as a ceiling for the first half: aim to reach halfway a few seconds per mile slower than goal, and spend what's left in the back half. Run the majority of your weekly volume easy — the goal pace belongs to a small share of your training, not most of it. Re-run the numbers after a tune-up race; if you can't hold even splits in that race, the goal pace is the thing to adjust, not the plan.

Common questions

How do I calculate my running pace?

Divide your finish time by the distance. A 20:00 5K over 3.107 miles is 6:26 per mile; the same run over 5 kilometres is 4:00 per kilometre. Pace is just time ÷ distance — the calculator handles the unit conversion so you don't round the factor.

How do I convert min/mile to min/km?

Divide the per-mile pace by 1.609344 (the exact miles-to-km factor). An 8:00/mi pace is 4:58/km. Going the other way, multiply the per-km pace by the same number. This calculator shows both at once.

Can I use my 5K pace to set my marathon pace?

No. Pace decays with distance — even the world records slow about 33 sec/mi from the 5K to the marathon. A pace calculator does arithmetic on one distance; predicting a time at a different distance needs a prediction formula (Riegel), which accounts for that decay.

Should I run even splits or negative splits?

Even to slightly negative is the durable approach for most races. The split table here is even by construction; treat it as the ceiling for the first half rather than a target to beat early. Banking time by going out fast tends to cost more later than it saves.

How much of my training should be at goal race pace?

Not much. Polarised-training work (Seiler 2010) supports roughly 80% of running easy and about 20% hard, with little time at the moderate pace that goal-pace running usually falls into. Goal pace is for a handful of key sessions and race day, not for most of the week.