How to Calculate Wind Chill: Formula, Steps, and Examples

Wind chill is how cold the air feels on exposed skin once the wind is factored in. On a still day your skin sits inside a thin layer of warmer air that it heats itself. Wind strips that layer away, so heat leaves your body faster and it feels colder than the thermometer reads. This guide gives you the exact formula, walks through a full worked example, adds the metric version and a quick reference chart, and flags the mistakes people most often make so your numbers come out right the first time.

What is the wind chill formula?

The current wind chill formula is the one adopted by the US National Weather Service and Environment Canada in 2001, replacing the older 1945 Siple and Passel model. It was rebuilt around modern heat-transfer science and human face-cooling trials, which is why it reports higher (less alarming) numbers than the version your parents grew up with. In Fahrenheit and miles per hour it is:

• WC is the wind chill (feels-like) temperature in degrees Fahrenheit.
• T is the measured air temperature in degrees Fahrenheit.
• V is the wind speed in miles per hour.
• V^0.16 means the wind speed raised to the power of 0.16.

The exponent term (V^0.16) is what trips most people up, so we will handle it carefully in the worked example below. If you would rather skip the arithmetic, the wind chill calculator does it instantly. You can read the official method on the National Weather Service wind chill page.

When does the wind chill formula apply?

The formula is valid only for temperatures at or below 50 F and wind speeds above 3 mph. Outside that range it is not meaningful, which is why you never see a wind chill quoted on a warm or nearly calm day.

• Temperature at or below 50 F. Above this, the body loses little heat to wind convection, so no wind chill value is reported.
• Wind above 3 mph. Below roughly 3 mph the air is close to still, and the formula would actually return a value slightly higher than the real temperature, which is why it is capped out of range.
• Wind measured at face height. The 2001 model assumes wind speed at about 5 feet (the average adult face), not the 33-foot height that standard anemometers use, so official reports scale the raw wind reading down before applying the formula.
• Exposed skin. Wind chill describes bare skin exposure. Clothing, shelter, and sunlight all change how cold you actually feel.

How do you calculate wind chill step by step?

To calculate wind chill by hand, raise the wind speed to the 0.16 power, build the four terms, then add and subtract them. Let us work an air temperature of 20 F with a wind speed of 15 mph. Follow these steps in order.

1. Write down your inputs. T = 20 and V = 15.
2. Raise the wind speed to the power 0.16. 15^0.16 is about 1.5423. On a calculator, enter 15, press the power (x^y or ^) key, enter 0.16, and press equals.
3. First term: the constant 35.74.
4. Second term: 0.6215 times T = 0.6215 times 20 = 12.43.
5. Third term: 35.75 times (V^0.16) = 35.75 times 1.5423 = about 55.14. This term is subtracted.
6. Fourth term: 0.4275 times T times (V^0.16) = 0.4275 times 20 times 1.5423 = about 13.19.
7. Add and subtract: 35.74 + 12.43 - 55.14 + 13.19 = about 6.22.
8. Round to the nearest whole degree: the wind chill is about 6 F.

So at 20 F with a 15 mph wind, exposed skin feels like roughly 6 F, a full 14 degrees colder than the thermometer. The single most common slip is step 2: people multiply 15 by 0.16 (which gives 2.4) instead of raising 15 to the 0.16 power (which gives about 1.54). If you are comfortable with exponents you may also enjoy our explainer on what a logarithm is, since powers and logs are two sides of the same coin.

How do you calculate wind chill in Celsius?

For Celsius and kilometres per hour, use the metric version of the same 2001 model: WC = 13.12 + 0.6215T - 11.37(V^0.16) + 0.3965T(V^0.16), where T is air temperature in degrees Celsius and V is wind speed in km/h. The metric formula applies at or below 10 C with wind above 4.8 km/h, which are the same physical conditions as the Fahrenheit limits.

You cannot mix units. Plugging Fahrenheit temperatures into the metric formula, or km/h into the Fahrenheit one, gives nonsense. If your data is in mixed units, convert everything to one system first, or let a tool handle it. The Fahrenheit and Celsius formulas are the same curve expressed in different units, so both give the same real-world feels-like reading once you convert the answer back.

Wind chill quick reference chart

Here is a small chart of feels-like temperatures from the 2001 Fahrenheit formula, rounded to the nearest degree. Read down for air temperature and across for wind speed.

Notice two patterns. First, colder air and stronger wind both push the feels-like number down. Second, the extra chill from added wind gets smaller as the wind rises: going from 5 to 10 mph drops it more than going from 20 to 30 mph. That flattening is exactly what the V^0.16 exponent produces, and it is the reason a gale does not keep making things colder without limit.

What wind chill means for frostbite risk

Wind chill matters because it predicts how fast exposed skin freezes, not just how uncomfortable you feel. The National Weather Service ties frostbite times directly to the wind chill value: around -19 F wind chill, frostbite can occur on exposed skin in roughly 30 minutes; near -35 F the window drops to about 10 minutes; and by roughly -60 F it can happen in under 5 minutes. Those thresholds are why winter storm warnings quote wind chill rather than raw air temperature.

Treat these as planning guides, not guarantees. Wet skin, sweat, contact with cold metal, and individual circulation all change real risk. The practical takeaway: once wind chill drops below about -18 F, cover every patch of skin and limit time outdoors.

Why does wind make it feel colder?

Wind makes it feel colder because it speeds up heat loss from your skin, not because it lowers the actual air temperature. Your body constantly warms a thin boundary layer of air against your skin. In still conditions that layer insulates you a little. Wind blows it away and replaces it with fresh cold air, so your skin gives up heat faster through convection. The thermometer still reads the same air temperature, but your body loses warmth as if it were much colder.

This is also why wind chill only describes exposed skin and not, say, the temperature of your car engine or a glass of water. Those objects are not actively generating heat the way your body is, so wind cools them toward the true air temperature but no lower. It is closely related to another cold-weather number, the dew point, which tells you about moisture and frost rather than perceived cold. Together they give a fuller picture of winter conditions.

Common mistakes when calculating wind chill

• Multiplying instead of raising a power. V^0.16 is not V times 0.16. You must raise the wind speed to the 0.16 power, which is a much smaller number and the single biggest source of wrong answers.
• Mixing units. The Fahrenheit formula needs T in F and V in mph; the metric formula needs C and km/h. Convert everything to one system before you start.
• Applying it out of range. Above 50 F, or at 3 mph or less, the formula does not apply and can even return a value above the air temperature, which is a red flag.
• Using raw anemometer wind. Official wind chill scales the measured wind down to face height. Feeding in a raw high-altitude gust overstates the chill.
• Confusing wind chill with the heat index. Wind chill is a cold-weather metric. For hot, humid days you want the heat index calculator instead, which combines temperature and humidity.
• Treating it as a health limit. Wind chill is a comfort and frostbite-risk guide, not a precise measure of body temperature.

If you would rather not do the exponent by hand, enter your temperature and wind speed below and get the feels-like value at once. The tool uses the same official 2001 NWS formula shown above.

Now you know exactly what wind chill means, when the formula applies, how to work it out in both units, and what the number means for frostbite. Keep the range in mind (at or below 50 F, above 3 mph), remember the V^0.16 exponent, and treat the result as a guide to how cold exposed skin will feel so you can dress for it and stay safe.