Wind Chill Calculator
Apply the 2001 North American wind chill formula in Fahrenheit or Celsius, with validity limits flagged and the frostbite exposure time for the result.
Low risk — frostbite unlikely for most people
Uncomfortable and cold. Dress in layers with a wind-resistant outer shell.
How this number was reached
- Air temperature = 5.0 °F (-15.0 °C)
- Wind speed = 25.0 mph (40.2 km/h)
- Twc = 35.74 + 0.6215T − 35.75V0.16 + 0.4275TV0.16 = -17.41 °F
- Twc = 13.12 + 0.6215T − 11.37V0.16 + 0.3965TV0.16 = -27.48 °C
- Validity: T ≤ 50 °F (10 °C) and wind ≥ 3 mph (4.8 km/h) — satisfied
This is the 2001 North American formula adopted jointly by the US National Weather Service and Environment Canada. It models the heat loss from a bare face walking at 3 mph into the wind, with the wind measured at 1.5 m rather than the 10 m of a standard weather report.
Wind chill at 5 °F for other wind speeds
| mph | km/h | Wind chill °F | Wind chill °C |
|---|---|---|---|
| 5 | 8.0 | -4.6 | -20.4 |
| 10 | 16.1 | -9.7 | -23.2 |
| 15 | 24.1 | -13.0 | -25.0 |
| 20 | 32.2 | -15.4 | -26.4 |
| 25 | 40.2 | -17.4 | -27.5 |
| 30 | 48.3 | -19.1 | -28.4 |
| 35 | 56.3 | -20.5 | -29.2 |
| 40 | 64.4 | -21.8 | -29.9 |
| 45 | 72.4 | -23.0 | -30.6 |
| 50 | 80.5 | -24.0 | -31.1 |
Notice how the curve flattens: the first 15 mph does most of the work, and doubling the wind again takes far less off. Frostbite bands follow the Environment Canada hazard table. These are estimates for general information, not medical advice.
What is the Wind Chill Calculator?
The ByteTools Wind Chill Calculator uses the 2001 North American formula adopted jointly by the US National Weather Service and Environment Canada.
- 2001 North American formula in both its imperial and metric forms
- Wind speed in mph, km/h, m/s or knots; temperature in °F or °C
- Validity limits enforced — results outside T ≤ 50 °F or wind ≥ 3 mph are dimmed and explained
- Environment Canada frostbite risk bands from low risk to under two minutes
- Table of wind chill at 5 to 50 mph for the temperature you entered
- Both formulas printed with your numbers substituted in
How to use the Wind Chill Calculator
- 1
Enter the air temperature and pick Fahrenheit or Celsius — switching units converts the number for you.
- 2
Type the wind speed and choose mph, km/h, m/s or knots.
- 3
Read the wind chill in both units and how much colder it feels than the thermometer says.
- 4
Check the coloured band for the frostbite exposure time at that wind chill.
- 5
Scan the table to see how the same temperature behaves at other wind speeds, then copy the results.
About the Wind Chill Calculator
The ByteTools Wind Chill Calculator uses the 2001 North American formula adopted jointly by the US National Weather Service and Environment Canada. In imperial form that is 35.74 + 0.6215T − 35.75V^0.16 + 0.4275·T·V^0.16 with temperature in °F and wind in mph, and the metric form 13.12 + 0.6215T − 11.37V^0.16 + 0.3965·T·V^0.16 works in °C and km/h.
The formula has published limits — it is defined at or below 50 °F (10 °C) and at wind speeds of 3 mph (4.8 km/h) or above — and this tool respects them. Step outside and the result is dimmed and labelled as an extrapolation rather than presented as a forecast. Inside the limits you get the Environment Canada frostbite band, from low risk down to frostbite in under two minutes.
Wind speed can be entered in mph, km/h, m/s or knots, and results are shown in both °F and °C alongside a table of the same temperature at other wind speeds. Everything is computed in your browser; nothing is uploaded. These are estimates for general information, not medical advice.
Frequently asked questions
What is the wind chill formula?
The 2001 North American formula is T(wc) = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275·T·V^0.16 for °F and mph. The metric version is 13.12 + 0.6215T − 11.37V^0.16 + 0.3965·T·V^0.16 for °C and km/h. Both replaced the older 1945 Siple–Passel formula, which overstated the cooling considerably.
At what wind chill does frostbite happen?
Environment Canada puts frostbite risk at 10 to 30 minutes below about −28 °C, 5 to 10 minutes below −40 °C, 2 to 5 minutes below −48 °C and under 2 minutes below −55 °C. The calculator names the band your result falls into along with what to do about it.
Why does the wind chill formula stop at 50 °F?
Because it was fitted to cold-weather heat-loss data from a bare human face. Above 50 °F (10 °C) wind barely changes how cold you feel, and the equation starts producing figures that mean nothing. The tool dims the answer and says so rather than pretending it is valid.
Does wind chill affect a car or a thermometer?
No. Wind chill describes heat loss from warm skin, so it only applies to people and animals. A parked car, a water pipe or a thermometer cools to the actual air temperature no faster in wind — wind just gets it there sooner, it does not take it lower.
Why does wind chill stop dropping so fast at high wind speeds?
The formula raises wind speed to the power 0.16, which flattens quickly. Going from 5 to 15 mph takes a big bite out of the apparent temperature, but going from 35 to 45 mph takes only a degree or two more. The table in the tool shows that curve at your own temperature.
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