How do I calculate my running pace?

Use the Pace Calculator to convert between pace, distance, and time. Enter your distance and time to get average pace, or enter target pace and distance to estimate finish time.

How can I predict my race time for a different distance?

The Race Time Predictor uses the Riegel formula to estimate equivalent performances from a recent race result, with standard race distances and optional custom targets.

What is Grade Adjusted Pace?

Grade Adjusted Pace converts pace on hills into an estimated flat-equivalent effort so you can compare hilly runs, trail races, and road efforts more fairly.

How do wind and heat calculators help race planning?

The wind and heat calculators estimate how weather can change pace and race time, helping runners set realistic targets for headwinds, tailwinds, humidity, and hot conditions.

Which calculator should I use for a course-specific race plan?

Use the Race Planning Calculator when you have a target time or GPX file and want split planning, terrain-adjusted pacing, fueling, hydration, and PDF export.

How much does altitude slow your running down?

It depends on the altitude, the race distance and your fitness, but as a rough anchor: at 2,000 m an unacclimatized runner loses somewhere around 6-8% on a 5K and rather more over a marathon, and individual variation of a quarter either side of that is normal. The measured reference point this calculator is built around is a 3,000 m time trial at 2,100 m running about 9.7% slower than sea level. The loss grows roughly with altitude and with race duration, and it is steeper for fitter runners: a trained athlete loses about 6.3% of VO₂max per 1,000 m of altitude, an untrained one about 5.3%.

At what altitude does running actually get harder?

Lower than most runners assume. Careful chamber measurements find VO₂max already significantly reduced at 800 m in trained athletes, with no obvious threshold below that — the decline is close to linear from very low altitudes upward, and trained runners start losing sooner than untrained ones (around 900 m against around 1,200 m). What changes higher up is that the loss becomes big enough to notice in a session rather than only in a lab. Around 1,500 m most runners feel it in a hard effort; above 2,500 m it dominates everything, and altitude sickness becomes a separate concern.

How long does it take to acclimatize to altitude?

The useful adaptations run over two to three weeks: plasma volume adjusts within days, ventilation shifts in the first week, and red cell mass takes two to four weeks to move meaningfully. Racing at altitude the same day you arrive is sometimes better than racing on day two or three, when the acute response is at its worst — but if you have more than about a week, more is better. What acclimatization cannot do is restore VO₂max: it stays depressed for as long as you are up there. What it restores is your ability to run at a given submaximal effort comfortably, which is most of what a race feels like.

Why were sprint world records set at the 1968 Mexico City Olympics?

Because the two effects of altitude push in opposite directions, and in a sprint only one of them matters. Thin air holds less oxygen, which ruins endurance events, but it also produces less aerodynamic drag, which helps anything decided by raw speed. At 2,240 m the drag saving is worth more to a 200 m runner than the missing oxygen costs them, so records fell across the short events and the long jump, while the distance finals were won in times far off the same athletes' sea-level form. The crossover sits somewhere below 800 m, which is why this calculator's shortest distance is 1500 m.

Should I adjust my training paces at altitude?

Yes for anything hard, and no for anything easy. Easy runs should be run on effort — the pace will be slower on its own and that is fine. For intervals, adjust the recoveries first and the rep paces second: at altitude the recovery between reps is where you fall behind, and cutting rest is the fastest way to turn a controlled session into a disaster. When you do adjust rep pace, use the sea-level → altitude direction of this calculator with the distance closest to your session's total quality volume. And when you come back down, do not read your altitude paces as a fitness drop — convert them back first.

Running Tools

Altitude Calculator

How much slower is the same effort at altitude? Enter a pace and an altitude and this converts between the two, for every race distance from 1500 m to the marathon.

Calculator Mode

Enter the pace you hold at sea level and see what the thin air turns it into.

Units

Choose your preferred unit system for altitude and pace

Your Sea-Level Pace

Minutes /km

Seconds /km

Event

The distance sets how long you are out there, and with it how much of the effort is aerobic — which is the part altitude takes away.

Altitude & Acclimatization

Altitude Above Sea Level (m)

Height above sea level — not the climbing you do during the run. The model covers 0 to 3,000 m (9,843 ft).

Altitude Acclimatization

Acclimatization gives some of the loss back, never all of it. VO₂max stays down for as long as you are up there; what recovers over two to three weeks is your submaximal performance.

⚠️ Important Notice

These are estimates for healthy runners going up to train or race, and the range is wide for a reason — the difference between two runners at the same altitude is larger than most people expect. Above about 2,500 m, altitude sickness becomes a risk in its own right (headache, nausea, broken sleep, breathlessness at rest) and no pace adjustment fixes that. Go up gradually, drink more than feels necessary, and treat the first two days as easy running whatever this calculator says.

About Running at Altitude

Air pressure falls with altitude, so every breath carries less oxygen. Your muscles still need the same amount, so the ceiling on aerobic power drops, and the longer the race the more of it sits under that ceiling. That is the whole mechanism — and it is why the correction here is not a single percentage but depends on the distance, on your fitness, and on how long you have been up.

Why Sprints Get Faster: Below roughly 800 m the sign flips. A sprint is almost entirely anaerobic, so the missing oxygen barely registers, while the thinner air genuinely reduces aerodynamic drag — and the runner goes faster. The 1968 Mexico City Olympics, held at 2,240 m, is the cleanest evidence there is: world records fell in every event up to 400 m and in the long jump, while the 5,000 m, 10,000 m, marathon and steeplechase were won in times well outside what those same fields ran at sea level. This calculator starts at 1500 m because that is the shortest distance where the aerobic loss reliably wins.

How the Correction Is Built: Four steps, in order. VO₂max falls with altitude — about 6.3% per 1,000 m for trained runners in the hypobaric-chamber measurements this uses (Wehrlin & Hallén, 2006), less for untrained ones. Only part of that reaches your race, because you race at a fraction of VO₂max and that fraction depends on how long the race lasts. Thinner air then returns a little through reduced drag. Acclimatization recovers part of what is left. The result is anchored to a measured performance rather than to theory: a 3,000 m time trial at 2,100 m runs about 9.7% slower than the same runners at sea level.

What Acclimatization Does and Doesn't Do: Two to three weeks high up raises red cell mass and restores much of your submaximal performance, but VO₂max at altitude stays down the whole time you are there — you do not get it back by staying. That is why the fully acclimatized setting reduces the cost instead of removing it. Coming back down, the benefit is real but modest, and it fades over two to three weeks.

Training by Effort, Racing by Numbers: Above about 1,200 m, run easy days on effort and let the pace be whatever it turns out to be. Sessions are what need real thought, and the recovery is what changes most — lengthen recoveries before you slow the reps down. If you train high and race low, the paces you hit up there are not the paces to plan a sea-level race around: convert them with the second mode of this calculator first, which is exactly what the coaching platform does automatically with every activity that syncs in.

Frequently Asked Questions

Related Running Calculators

Heat & Humidity Calculator Grade Adjusted Pace Calculator Race Planning Calculator Running Pace Calculator

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