The formula
How to calculate wind chill
Wind chill describes how much faster wind strips heat away from exposed skin than still air would, expressed as the still-air temperature that would feel equally cold. It only applies in cold conditions — the formula assumes heat is flowing out of the body, which is not the relevant physics on a warm day.
The exponent on wind speed (v^0.16) reflects that the cooling effect of wind is strongest at low speeds and rises more slowly as it gets stronger — the jump from still air to a light breeze matters far more to how cold it feels than the same jump from a strong wind to an even stronger one.
What to enter:
- Air temperature (°C)
- Wind speed (km/h)
No submit button: type and the answer moves. Your inputs end up in the link, so the page can be shared already filled in.
Where more decimal places matter than the fields above display, the underlying calculation is not rounded until the final figure is shown — the precision used internally is higher than what is printed, which matters for anyone chaining this result into a further calculation of their own.
Why wind chill matters
This kind of calculation comes up in coursework, in a laboratory or field setting, and in professional practice, and the arithmetic is identical in every case — only the numbers being fed into it, and what is riding on getting them right, actually change.
Beyond a single check, the same calculation is worth rerunning whenever a measured input changes — a new reading, a corrected value, an updated assumption — since the result here always reflects exactly what is currently in the fields above rather than a value calculated once and then left stale.
This calculation sits in a long tradition of being done first by hand with tables and slide rules, then with a scientific calculator, and now with a page like this one — the underlying mathematics has not changed at any point in that history, only the speed and convenience of getting from the inputs to the answer. Understanding the formula itself, shown above, is still worth doing even when a tool computes it instantly, since it is what makes the result trustworthy rather than just fast.
In practice, a formula like this one is most often reached for at the exact moment a manual calculation needs checking against a deadline — a lab report due, a problem set to submit — which is precisely the situation where a small arithmetic slip is easiest to miss and most costly to leave uncorrected. Running the same inputs through an independent calculator catches that class of error reliably.
Worked example
Here is the calculation with the starting values:
- Air temperature: 0 °C
- Wind speed: 20 km/h
That gives:
- Wind chill: -5.2 °C
The figures above are the calculator's own default values, shown purely so the working is visible rather than hidden — the same steps apply exactly to your own numbers, entered in the fields at the top of this page.
Reading the result
A wind chill of −15 °C does not mean the air itself has cooled to −15 °C — a thermometer still reads the actual air temperature. It means exposed skin loses heat at the same rate it would in still air at −15 °C, which is the figure that matters for frostbite risk and dressing appropriately.
Where this goes wrong. The formula used here is only meaningful at air temperatures at or below roughly 10 °C and wind speeds above about 5 km/h — below that threshold, or at higher temperatures, the calculation is not valid and the output should not be relied on. It also assumes exposed skin; wind chill is largely irrelevant to a body fully covered by wind-resistant clothing.
A result that is wrong by an exact factor of ten, a hundred or a similar round number is almost always a units error rather than a mistake in the formula itself — checking each input against the unit stated beside it is the fastest way to track it down.
No — wind chill is specifically about how fast a warm object (like skin, which generates its own heat) loses heat to moving air. An unheated object like a pipe or a parked car eventually reaches the actual air temperature regardless of wind, not the wind chill figure.
Frostbite risk guidance from meteorological agencies typically flags exposed skin at increasing risk as wind chill drops below about −25 °C, with the time to frostbite shortening rapidly as it falls further — but individual factors (clothing, circulation, duration outside) matter as much as the number itself.
The headline figure is wind chill. With 0 °C air temperature and 20 km/h wind speed, that comes to -5.2 °C. Change any field and the figure moves with it.
Generally, no more than the least precise input justifies — a result reported to six decimal places from inputs measured to two significant figures is implying a precision the calculation does not actually have. The calculator shows full precision so you can round appropriately for your own use.
Yes — the equation shown in the formula section above is the standard form used in textbooks and reference material for this calculation, not a simplified or approximate version.
Yes, in the sense that it applies the correct standard formula and returns an accurate result for the inputs given — but check your own course or publication's requirements for how results should be rounded, presented and referenced, since those conventions vary and are not something a calculator can know on your behalf.