Track wind calculator

How to use

This app calculates the effects of wind on your pace when running on a 400m athletics track. It is a companion app to my wind calculator for runners, which is designed for running on the roads.

To use the calculator, all you need to know is the wind speed, wind direction (relative to the track) and your running pace—either your actual pace in the wind, or the effort level you'd be aiming for if it were a calm day.

The track wind calculator supports different rep distances and different input units for wind speed, and allows you to adjust for various levels of shielding from the surrounding area that may reduce your exposure to the wind.

You can set the wind direction manually by dragging the wind icon around the dial, or use the compass rose buttons to “snap” the wind direction to a specific direction.

If you are doing repeats that involve a non-integer number of laps (for example, 200m, 600m, or 1 km repeats) you can select the appropriate button below the pace input, and the calculator will correctly account for the fact that, depending on the wind orientation, you spend different amounts of time in the wind.

These non-integer repeat distances also have an alternative (“alt”) variant for situations where you start them at the common finish line—which can be a useful strategy for doing workouts on windy days.

How this app works

This app implements all the same drag force and air resistance calculations for runners that I used in my wind calculator, but with some additional considerations for running on a track.

Compared with running in a straight line on a windy day, track calculations are more complex. That's because, as you circle the track, you spend some time with a headwind and some time with a tailwind. Headwinds slow you down more than tailwinds speed you up, so the net effect of wind is still detrimental.

Since tracks are not a perfect circle, the orientation of the wind relative to the track matters too. All else equal, it's better to have a cross-wind on the straightaways versus a headwind on the homestretch and a tailwind on the backstretch, since you spend less time going straight into the wind with the crosswind setup.

To deal with the changing effects of the wind on the curves, this calculator uses numerical integration: each curve is split up into a large number of very small straight-line segments, whose effects are calculated individually and then added up.

Is this wind app accurate?

Yes, as detailed in this write-up, this app's metabolic cost calculations are based on state-of-the-art physiology and biomechanics, and its predictions have been validated on real wind tunnel data. The predicted changes in metabolic cost are highly accurate for wind speeds of up to 15 mph (24 km/h).

For wind speeds above about 20 mph (32 km/h), this model is slightly too pessimistic: it predicts you will run a little slower than you actually will. The reason for this discrepancy at very high wind speeds is quite interesting: in an extreme headwind, people naturally lean forward into the wind. This forward lean lets them use their torso like a wing, generating an upward lifting force that modestly reduces the metabolic cost of running!

I am not aware of any wind tunnel data testing the effects of extreme tailwinds (or any tailwinds beyond the effective “still air” speed, e.g. a 16 km/hr tailwind when running at 16 km/hr), so consider these calculations tentative in cases where you have extraordinarily strong winds.

Limitations at very high speeds

This calculator relies on empirical data from physiology studies on the metabolic cost of running. Because of limitations in how energetic cost is measured—it is not possible to measure metabolic cost at speeds above a runner's maximal metabolic steady-state—the metabolic cost of speeds faster than about 5:20/mi or 3:20/km (80.0 per 400m) needs to be extrapolated from known data.

These extrapolations are pretty good at intermediate speeds (e.g. 3:00/km), but for extremely fast speeds—e.g. sub-50-second 400m pace—I would not trust this calculator very much, because the metabolic cost data will be very uncertain.

Also, the limitations mentioned earlier regarding extreme headwinds start to apply even in moderate winds when you are running very fast. At 50.0 per 400m, even in calm air you are encountering a self-generated headwind of about 18 mph / 29 km/h, which is well into the range of headwinds where the drag force model starts to diverge from experimental data.

In practice, elite-level sprinting probably requires purely data-driven empirical adjustments. For the 100m and 200m, try Jeff Chen's sprint calculator here, which is based on this scientific paper. I am not aware of any similar treatment for the 400m, because trackside wind data are not typically recorded during that event.

Setting your rep distance

The track wind calculator offers a number of rep settings beyond simply 400m repeats. When doing workouts on a windy day, it can often be advantageous to use repeats that use a non-integer number of laps—for example, 200m, 600m, or 1000m repeats—so you can get “more help” from the wind.

For example, a standard 600m repeat (starting at the 200m starting line on the track) involves running the homestretch twice, but the backstretch only once. So, if you have a strong headwind on the backstretch, doing 600m repeats can be a better choice than, say, 800m repeats.

Depending on the wind direction, you may want to do these repeats with an alternative (“alt”) starting line to take advantage of tailwinds. The calculator supports this “alt” option for 200m, 600m, and 1000m repeats.

Sometimes, you may be running continuously on the track, but using pace (in minutes per mile or minutes per kilometer) from your watch as a guide for your workout. In this case, you can use the “/mi” and “/km” settings, which calculate the effects for one full 400m loop, but with input and output pace expressed as /mi or /km.

This setting is useful for a workout like 10 km continuous on the track on a windy day—afterwards, you'll know your average pace in min/mi or min/km. Using the /mi or /km mode in the calculator can quickly convert this to a “wind-adjusted” pace (and treating it as a single 400m lap is appropriate, since the average effect of the wind over one 400m lap is the same as the average effect over many 400m laps).

Track configuration

This calculator assumes a standard track made to World Athletics specifications with a radius (to the actual running line, not the kerb) of 36.5 meters, which works out to curves of approximately 116 meters and straights of approximately 84 meters. Various changes to track design can result in small differences in these parameters but their influence on the effects of wind on your pacing is negligible.

So far, this calculator does not incorporate running in outer lanes, for two reasons. First, for inner lanes (e.g. lane 2 or 3) the difference just isn't going to be very big. Second, tracks differ in their lane width, which affects the geometry of the problem.

In the US, high school tracks have lanes that are only 42 inches wide, whereas World Athletics standard tracks have 48 inch wide lanes. It's probably not a huge effect but it's enough that I'd want to build it into the calculator before adding this feature.

Actual pace vs. calm-day effort

This calculator can start from either the pace you actually ran in the wind, or the calm-day effort you were aiming for. The default is actual pace: the split you actually ran in windy conditions. With this setting, the track wind calculator will estimate the pace you would have run if you had been running on a calm day.

When planning workouts, you often know what your calm-day effort would be—but you want to find out the actual pace you should expect to run, given the wind you'll be running in. If this is what you want, flip the toggle to enter “effort mode.” With this setting, the track wind calculator will estimate the actual speed you will run today given the wind you're facing, and given your calm-day effort level.

Constant effort vs. constant pace

When running on the track on a windy day, there are two possible strategies you could adopt: running at a constant effort, or running at a constant speed.

Constant effort is the default setting, because it is the more typical case: you aim for the right effort, allowing the wind to speed you up or slow you down depending on your position on the track.

If you monitor your training intensity using “running power” on devices that include wind sensors, like the Stryd pod and more advanced GPS watches from Garmin and COROS, these metrics are essentially trying to capture constant effort.

However, in some cases you may find yourself running at a constant speed, increasing your effort to maintain a given pace when you face headwinds, and backing off your effort when you have a tailwind.

This might happen if you are being asked to pace very precise splits for another runner, or if you are following an external pacing aid, like a Wavelight, Tempo Trainer (“the poor man's Wavelight”), or the speed display on your GPS watch.

As your intuitions would suggest, it is preferable to run a constant effort in the wind, as opposed to maintaining a constant speed. The reasons for this effect are pretty subtle; they involve a trade-off between spending more time in a headwind (because you are running slower to maintain a constant metabolic power output) versus increasing your metabolic power output to maintain the same speed.

Ultimately, the increase in metabolic power required to maintain the same speed “costs” more and dominates the balance, due to the squared relationship between relative airflow and drag forces.

In realistic conditions, the differences between constant-speed and constant-effort running in the wind only amount to a few tenths per 400m, so it's not a huge difference outside of elite-level competition. Nevertheless it is worth keeping in mind.

Do note that the constant effort vs. constant pace setting only applies to the actual time you ran in the wind. On a calm day, there is no difference between the two: because you face the same effective (self-generated) headwind at every point on the track, constant-effort running is constant-pace running in calm conditions.

Wind profile adjustments

When you check the weather forecast and you see a wind reading of “10 mph” or “16 km/h,” what you see is a reading from (or a forecast for) a standard weather monitoring station mounted ten meters (33 feet) above the ground in a place that is relatively unobstructed by tall buildings, trees, etc.

When running on a track, you usually experience less actual wind at chest level, for two reasons: you are closer to the ground, and you have the benefit of shielding (trees, bleachers, etc), which both diminish the wind speed.

Atmospheric scientists have developed a wind profile power law that describes how the actual wind speed falls off as a function of height, given some information about the surrounding location and its shielding (captured in a parameter called alpha, α).

The track wind calculator has four settings for α, based on typical values seen in urban, suburban, and rural settings. This table details recommended usage:

Setting	α	Recommended Wind Profile Mode
Urban	0.40	Urban areas with tightly-packed tall buildings, dense forests
Suburban	0.30	Suburbs, town center, park with trees and buildings
Rural	0.16	Rural road, open prairie, grasslands, athletics fields
None	0.00	Exposed mountain ridge, true ground-level wind measurements (e.g. wind gauge for track events)

The default setting is “suburbs,” simply since that's the one that's most representative for the tracks I typically use.

Notably, if you have access to a tube-style wind gauge (like the ones used to record wind speed in the 100m, 200m, etc. at track meets), you should use “None” for α and you can use the actual wind speed (in m/s) measured by that wind gauge.

However, when measuring the actual wind speed, you need to point the wind gauge directly into the wind—this is not how wind gauges are used in competition for the sprint/jump events (for official uses they are pointed down the homestretch).

Drafting behind other runners

Drafting in the wind can significantly reduce the effects of wind on your energetic expenditure during running. Currently, this calculator does not incorporate the effects of drafting, though I may incorporate “drafting mode” as an advanced feature at a later date.

Interestingly even the lead runner in a group experiences a small benefit, compared with running alone: the presence of a runner behind you diminishes the backwards pull created by the low-pressure void left behind you as you push the air aside.

Calculator settings

This calculator will remember your settings in your browser's local storage. So, when you come back to the calculator later, you'll be able to pick up where you left off. You can reset all settings to their defaults using the button.

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