The short answer
Running into the wind slows your pace more than a tailwind speeds it up. At the same effort, a 20 km/h (12 mph) headwind turns 5:00 per km (8:03 per mile) into about 5:24 (8:42), while the same tailwind gives only 4:52 (7:51). That headwind costs about as much as a 2% climb.
Key takeaways
- Air resistance rises with the square of the air speed, so headwinds cost more than tailwinds return.
- A 20 km/h (12 mph) headwind turns 5:00 per km (8:03 per mile) into 5:24.
- A 5% climb slows the same runner to about 6:01 per km (9:41 per mile).
- Downhill gives back less than uphill takes; steep descents slow you again.
On this page
Words this guide uses
- Headwind
- Wind blowing against your direction of travel. Forecasts give wind at 10 m (33 ft); at running height it's weaker.
- Grade-adjusted pace
- Your pace on a slope converted to the flat-ground pace that would take the same effort.
- Equal effort
- Running at the same metabolic power as you would on flat ground in still air, and letting pace change.
- Pace-timed forecast
- The weather for each stretch of your route at the time you'll run it.
How much does running into the wind slow your pace?
Running into the wind costs pace because air resistance grows with the square of the air speed hitting you. At the same effort, a 20 km/h (12 mph) headwind slows a 5:00 per km (8:03 per mile) runner to about 5:24 (8:42).
Wind sits alongside heat in running in heat and humidity: it changes your pace and how well you cool. The table holds effort steady on flat ground. Forecast wind is measured at 10 m (33 ft), so we use two-thirds of it at running height.
| Forecast wind, km/h (mph) | Flat pace 4:00 per km (6:26 per mile) | Flat pace 5:00 per km (8:03 per mile) | Flat pace 6:00 per km (9:39 per mile) |
|---|---|---|---|
| 10 (6) headwind | 4:09 (6:41) | 5:10 (8:19) | 6:11 (9:57) |
| 20 (12) headwind | 4:21 (7:01) | 5:24 (8:42) | 6:26 (10:22) |
| 30 (19) headwind | 4:36 (7:25) | 5:42 (9:10) | 6:47 (10:55) |
| 40 (25) headwind | 4:54 (7:53) | 6:03 (9:45) | 7:12 (11:36) |
| 20 (12) tailwind | 3:51 (6:12) | 4:52 (7:51) | 5:53 (9:28) |
To see the wind for each stretch of your own route at the time you'll run it, drop the route into Map your run.
Why does a headwind cost more than a tailwind gives back?
Because air resistance rises with the square of the air speed, and you spend longer on the slow leg. Into the wind, you push through your speed plus the wind's.
The physiologist Griffith Pugh measured this in 1971. Oxygen use rose with the square of the wind speed. A 65 kg (143 lb) athlete running at marathon speed, 4.45 m/s or 3:45 per km (6:02 per mile), used 3.0 litres of oxygen a minute in still air. Against a 67 km/h (41 mph) wind, that rose to 5.0 litres.
On calm days, air resistance is still part of the bill. Pugh estimated it at 7.5% of the energy cost at middle-distance speed on a track, and 13% at sprint speed.
The out-and-back proves the point. At 5:00 per km (8:03 per mile), a 10 km (6.2 mile) loop out and back costs about 1 minute 22 seconds in a 20 km/h (12 mph) wind, at equal effort. In a 30 km/h (19 mph) wind it costs about 2 minutes 36 seconds.
How much do hills slow your pace?
A lot uphill, a little help downhill. At equal effort, a 5% climb turns 5:00 per km (8:03 per mile) into about 6:01 (9:41), and a 10% climb into about 7:07 (11:28).
The energy figures come from Alberto Minetti and colleagues (2002), who measured ten runners on a treadmill from −45% to +45%. Running cost 3.40 J per kg per metre on the level, 18.93 J at +45% and as little as 1.73 J at −20%. Real runners don't fully follow the energy cost, so our model damps it toward real paces.
| Gradient | Energy per metre vs flat (Minetti) | Pace at equal effort, from 5:00 per km (8:03 per mile) |
|---|---|---|
| +10% | 1.66× | 7:07 per km (11:28 per mile) |
| +5% | 1.30× | 6:01 per km (9:41 per mile) |
| +2% | 1.11× | 5:23 per km (8:40 per mile) |
| Flat | 1.00× | 5:00 per km (8:03 per mile) |
| −2% | 0.90× | 4:38 per km (7:27 per mile) |
| −5% | 0.76× | 4:33 per km (7:19 per mile) |
| −15% | 0.51× | 5:00 per km (8:03 per mile) |
Downhill gains stop at about 10% faster, because your legs and braking set the pace, not your lungs. On steep descents you slow down again.
Is a headwind worse than a hill?
A strong headwind can be. For a 5:00 per km (8:03 per mile) runner, a 20 km/h (12 mph) headwind costs about as much as a 2% climb, and a 40 km/h (25 mph) one as much as a 5% climb.
The difference is that a hill ends and pays some back on the way down. A headwind along an exposed seafront, from Cape Town's Sea Point promenade to Chicago's lakefront, can last for kilometres. The wind also feels colder at pace: our guide to feels like temperature for runners explains why.
How should you pace wind and hills?
Run by effort, not by the pace on your watch. Let the pace drop into the wind and up the hills, and take the gift back when it comes.
- Set effort targets. Heart rate or breathing keep you honest when pace stops meaning much.
- Tuck in. Pugh found running 1 m (3 ft) behind another runner virtually eliminated air resistance at middle-distance speed.
- Plan the route. Run into the wind while you're fresh, and come home with it behind you.
- Time the run. Check the wind for your start time, not the day's average. Our guide to the best time to run in hot weather covers timing for heat.
- Use the right file. A route file with elevation gives you per-km climbs; see weather along your running route.
Racing a hilly course? Open it on a race page, such as South Africa's Comrades Marathon, to see where the climbs fall at your pace.
Questions runners ask
Does a tailwind make up for a headwind on an out-and-back run?
No. On a 10 km (6.2 mile) out-and-back at 5:00 per km (8:03 per mile), a 20 km/h (12 mph) wind costs about 1 minute 22 seconds at equal effort. In a 30 km/h (19 mph) wind it's about 2 minutes 36 seconds. You spend longer on the slow headwind leg, and air resistance grows faster than linearly.
Does drafting work for runners?
Yes, and the effect is measurable. Griffith Pugh found in 1971 that running 1 m (3 ft) behind another runner virtually eliminated air resistance and cut oxygen use by 6.5% at middle-distance speed. In a marathon pack or a parkrun with a strong headwind, tucking in on the exposed stretches is worth more than any gadget.
How much faster can you run downhill?
Less than you'd think. On a gentle descent, our model lets you run up to 10% faster at the same effort: 5:00 per km (8:03 per mile) becomes about 4:33 (7:19). On grades steeper than about 10%, your legs brake and pace slows again. Minetti's study found running's energy cost was lowest at a 20% descent.
Should I run into the wind first?
On an out-and-back, it usually helps. You face the hard leg while fresh and come home with the wind behind you when you're tired. On a cold day, it also means the chilling headwind comes before you're sweaty. Check the wind direction for your start time, not just the speed, because it can shift during a long run.
Is grade-adjusted pace the same on every app?
No. Each app uses its own model, so the same climb can show different adjusted paces. Map your run starts from Minetti and colleagues' 2002 energy-cost measurements, then damps them toward the pace real runners hold on slopes. Compare like with like: use one app's adjusted pace across runs, rather than mixing numbers from different apps.
See the heat at your pace.
Drop in your route (GPX, FIT or TCX), pick the day and your pace, and see the feels like, dew point and heat stress for every kilometre, timed to when you’ll be there. Free, in your browser, no sign-up.
Sources and method
- The Journal of Physiology (1971). The influence of wind resistance in running and walking and the mechanical efficiency of work against horizontal or vertical forces (Pugh)
- Journal of Applied Physiology (2002). Energy cost of walking and running at extreme uphill and downhill slopes (Minetti et al.)
Paces come from the RunFast engine at equal metabolic power. Runner: 70 kg (154 lb), drag area 0.24 m² standing upright (Pugh, 1971), muscle efficiency against the air 25%, air density at sea level and 15 °C (59 °F). The climbing cost uses Minetti et al.'s (2002) energy-cost equation for running on slopes. For pace on slopes the engine damps Minetti's equal-energy result (raised to the power 0.7) toward the paces real runners hold, caps downhill gains at 10%, and slows steep descents beyond −10%. Wind is the 10 m forecast wind; at running height (about 1.5 m, 5 ft) the engine uses two-thirds of it. Headwind and tailwind cases are straight into and straight behind the runner on flat ground. The out-and-back case is 5 km out and 5 km back. Equal-effort paces were found by solving for the speed at which power in the wind matches power in still air. Imperial values are our conversions.
Wes Thomson
Wes Thomson builds RunFast, which times the heat, humidity and dew point to a runner's own pace along the route, and its sister Windline, live wind forecasts for cyclists. Both run on the same forecast engine. He writes these guides with one focus: what the weather will do to your run, kilometre by kilometre, and how to plan around it.