How much slower do you run at altitude?
At altitude the air pressure is lower, so each breath delivers less oxygen to your muscles. Your maximal aerobic capacity (VO2max) falls and any race that relies on aerobic energy, which is every distance from about 1500 m upwards, gets slower. How much slower depends on the altitude and, just as much, on how long you have been there.
No single number fits everyone, so this calculator gives two research-based estimates and shows the range between them:
Acclimatised
Jack Daniels’ published rule for runners living or training at altitude: no change up to 3,000 ft (914 m), then about 1.2 % slower for every 1,000 ft above that. This is the estimate to use for training paces at altitude.
On arrival
Based on the measured fall in VO2max of about 6.3 % per 1,000 m above 300 m in sea-level athletes (Wehrlin & Hallén, 2006). It is the upper estimate for a sea-level runner racing within a few days of arriving.
Most runners land between the two. A week or two at altitude moves you towards the acclimatised figure, but a sea-level runner never fully regains sea-level performance at altitude.
The formulas
On arrival: time factor = 1 ÷ (1 − 0.063 × (altitude in m − 300) ÷ 1,000) (no change below 300 m)
Between two altitudes: time at B = time at A × factor(B) ÷ factor(A)
The on-arrival formula assumes that running economy is unchanged at moderate altitude, so speed at the same relative effort falls in proportion to VO2max. The reduced air resistance at altitude helps a little, but at distance-running speeds the effect is small, so it is left out.
Altitude slowdown table
| Altitude | Acclimatised | On arrival | 4:00:00 marathon becomes | 50:00 10K becomes |
|---|---|---|---|---|
| 0 m (0 ft) | +0.0 % | +0.0 % | 4:00:00 – 4:00:00 | 50:00 – 50:00 |
| 500 m (1,640 ft) | +0.0 % | +1.3 % | 4:00:00 – 4:03:04 | 50:00 – 50:38 |
| 1,000 m (3,280 ft) | +0.3 % | +4.6 % | 4:00:49 – 4:11:04 | 50:10 – 52:18 |
| 1,500 m (4,920 ft) | +2.3 % | +8.2 % | 4:05:32 – 4:19:38 | 51:09 – 54:05 |
| 2,000 m (6,560 ft) | +4.3 % | +12.0 % | 4:10:15 – 4:28:47 | 52:08 – 56:00 |
| 2,500 m (8,200 ft) | +6.2 % | +16.1 % | 4:14:59 – 4:38:37 | 53:07 – 58:03 |
| 3,000 m (9,840 ft) | +8.2 % | +20.5 % | 4:19:42 – 4:49:11 | 54:06 – 1:00:15 |
Daniels’ altitude adjustments for training paces
Jack Daniels advises slowing threshold and interval paces at altitude, by roughly these amounts compared with sea level:
| Altitude | Slower by (per mile) | Per 400 m |
|---|---|---|
| 4,000 ft (1,220 m) | 4–5 s | about 1 s |
| 5,000 ft (1,525 m) | 8–10 s | 2–3 s |
| 6,000 ft (1,830 m) | 12–15 s | 3–4 s |
| 7,000 ft (2,135 m) | 16–20 s | 4–5 s |
| 8,000 ft (2,440 m) | 20–25 s | 5–6 s |
- Repetitions (short, fast reps of a minute or two) are not slowed, because they rely less on aerobic energy. Take slightly longer recoveries instead.
- Easy and long runs: keep the effort, not the pace. Run by feel or heart rate and accept that the pace is slower.
- Marathon pace runs: use the acclimatised estimate above for your goal pace at altitude.
Converting a race run at altitude to sea level
Put the altitude where you raced in the From box and 0 in the To box (or press Swap). The result is your sea-level equivalent, which you can then use in the VDOT calculator or the race time predictor. If you live at altitude, the acclimatised figure is the fairer conversion; if you travelled to race, use the on-arrival figure.
When to arrive for a race at altitude
A common coaching approach for sea-level runners is either to arrive as late as possible, within about 24 hours of the start, before poor sleep and dehydration build up, or to arrive at least two weeks early so that breathing and heart-rate responses have time to adapt. Arriving three to seven days before is often considered the least favourable option. Whichever you choose, start conservatively: the first half of an altitude race feels deceptively easy.
Altitude sickness. Above about 2,500 m some people develop headache, nausea or poor sleep. Ease off on the first days, drink enough and descend if symptoms get worse. These estimates are for healthy runners and are not medical advice.
Altitude is not the same as hills
This calculator covers the altitude above sea level where you run. Climbing and descending during a run is a different effect; for that, use the grade adjusted pace calculator. For hot or humid race days, combine this with the heat pace calculator.
Limits: the models are reasonable from sea level to about 3,000 m. Above that, losses grow faster and the estimates are likely too optimistic. For events shorter than 1500 m altitude has little effect, and sprints can even be slightly faster in thin air (Hamlin, Hopkins & Hollings, 2015).
- Wehrlin JP, Hallén J (2006). Linear decrease in VO2max and performance with increasing altitude in endurance athletes. Eur J Appl Physiol 96:404–412.
- Daniels J. Ask a coach: how do you adjust threshold pace at altitude? V.O2 (2011).
- Hamlin MJ, Hopkins WG, Hollings SC (2015). Effects of altitude on performance of elite track-and-field athletes. Int J Sports Physiol Perform 10(7):881–887.
- Lara B, Salinero JJ, Del Coso J (2014). Altitude is positively correlated to race time during the marathon. High Alt Med Biol 15(1):64–69.
Last reviewed: September 2026 · Health disclaimer