Calculate Wind Chill: Formula, Examples, and Limits

Calculate wind chill by combining the air temperature and wind speed in the standard North American wind-chill formula; enter temperature in degrees Fahrenheit and wind speed in miles per hour. The result is an apparent temperature in °F, not a measurement of how cold the air or an object actually is.

Formula

The standard formula used here is:

W = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T V^0.16

• W is the wind-chill index, in degrees Fahrenheit (°F).
• T is the air temperature, in °F.
• V is wind speed, in miles per hour (mph).

This equation is designed for air temperatures at or below 50°F and wind speeds above 3 mph. Use the inputs in those units; entering Celsius or kilometres per hour without converting them produces an invalid result. The displayed result is rounded to one decimal place.

Worked Example

Using the calculator’s defaults, the air temperature is 20°F and wind speed is 15 mph. First calculate the wind-speed term:

15^0.16 ≈ 1.527

Then substitute into the formula:

W = 35.74 + (0.6215 × 20) − (35.75 × 1.527) + (0.4275 × 20 × 1.527)

W ≈ 35.74 + 12.43 − 54.59 + 13.06 = 6.64°F

Rounded to one decimal place, the wind chill is 6.6°F. The air itself is still 20°F; 6.6°F describes the calculated cooling effect on exposed skin under the formula’s conditions.

What Wind Chill Means

Wind chill describes how quickly wind removes heat from exposed skin compared with still air at the same temperature. A person loses heat to the surrounding air; moving air continually replaces the layer of air warmed near the skin, allowing heat to escape faster. The wind-chill index expresses that effect as an equivalent temperature in calm conditions.

It is an estimate for human exposure, not a universal temperature reading. A thermometer will not show the wind-chill value, and water, buildings, vehicles, and other objects do not cool below the actual air temperature solely because the wind is blowing. Wind can make them lose heat faster, but their temperature is governed by the actual environment and other sources of heat.

When to Use the Calculation

Use wind chill when assessing how cold outdoor conditions may feel to people, especially when deciding how to dress or how long to remain exposed. The number is most useful alongside the actual air temperature and wind speed, not as a replacement for either.

• At 20°F with a 15 mph wind, the formula gives about 6.6°F.
• At the same 20°F temperature with a 5 mph wind, the result is about 13.7°F.
• With no wind, this formula is outside its intended wind-speed range; do not treat a zero-wind calculation as a reliable wind-chill index.

These examples show why the wind speed matters. They do not mean every person will feel exactly the calculated temperature: clothing, activity, shelter, moisture, and individual differences affect heat loss.

Units and Common Calculation Mistakes

The displayed formula requires °F and mph. For metric observations, first convert temperature and wind speed: °F = (°C × 9/5) + 32, and mph = km/h ÷ 1.609344. For example, 20°C is 68°F and 20 km/h is about 12.4 mph. Because 68°F is above the formula’s 50°F limit, that example is not in its valid range.

• Mixing units: Putting °C into T or km/h into V can produce a plausible-looking but wrong number.
• Using the wrong wind speed: The equation expects wind speed in mph. A weather station’s reported wind may be measured at a height different from the standard conditions underlying the index.
• Rounding too early: Keep the intermediate value of V^0.16 unrounded when possible, then round the final answer.
• Confusing wind chill with air temperature: Report both when useful. Wind chill is an apparent-temperature index, not a thermometer reading.

Scope, Safety, and Limitations

The formula is intended for temperatures of 50°F or lower and wind speeds greater than 3 mph. Outside that range, its result should not be relied upon as a standard wind-chill estimate. In particular, it is not a heat-index formula for hot weather. Different reporting systems or local forecasts may use slightly different calculation and rounding practices.

Wind chill can help communicate exposure conditions, but it cannot predict an individual’s risk or provide a precise safe exposure time. Cold injury depends on factors beyond the index, including duration, wet clothing, shelter, and a person’s condition. Use practical protection: cover exposed skin, wear suitable dry layers, and seek shelter if conditions become uncomfortable or unsafe. Do not interpret a lower wind chill as the air itself reaching that temperature.

Frequently Asked Questions

How do you calculate wind chill by hand?
Convert the observations to °F and mph, calculate V^0.16, and substitute T and V into the formula shown above. Round only the final result.

Can I calculate wind chill in Celsius?
Yes, but this calculator uses the Fahrenheit equation. Convert °C to °F and km/h to mph before using it. Do not insert metric numbers directly into the formula.

Is wind chill the actual temperature?
No. It is an apparent-temperature index for the effect of wind on exposed human skin. A thermometer measures the actual air temperature.

Does wind chill apply when it is warm?
No. This formula is intended for air temperatures at or below 50°F and winds above 3 mph. It is not designed to describe hot-weather comfort.

Why does wind chill change when the wind gets stronger?
Stronger wind generally removes heat from exposed skin faster, so the formula returns a lower apparent temperature when other conditions are unchanged.

Related

• Chi-Square Test Calculation: Formula and Example
• Calculating a Z Test Statistic: Formula and Examples
• Calculating the Median: Formula, Steps, and Examples

in t | Air temperature | °F | 20
in v | Wind speed | mph | 15 | 0
out wc | Wind chill | °F | 35.74 + 0.6215 * t - 35.75 * v ^ 0.16 + 0.4275 * t * v ^ 0.16 | 1