Wind chill calculator
Uses the formula Canada and the United States adopted in 2001 — the one Environment Canada actually reports.
Free · no signup Runs in your browser
How is wind chill calculated?
Wind chill = 13.12 + 0.6215 × Ta − 11.37 × V^0.16 + 0.3965 × Ta × V^0.16, where Ta is the air temperature in degrees Celsius and V the wind speed in kilometres per hour. At −20 °C with a 30 km/h wind, the index is −33. It only applies at or below 10 °C with wind of at least 4.8 km/h, and it reports an equivalent temperature rather than a real one.
It is an equivalent temperature, not a real one
This is the point most often missed. A thermometer in a −20 °C wind still reads −20 °C. The wind chill index of −33 describes how fast exposed skin loses heat, expressed as the still-air temperature that would strip heat at the same rate.
That distinction has practical consequences. Wind chill predicts frostbite well, because frostbite is about heat loss from skin. It tells you nothing about whether your pipes will freeze, whether your car will start, or how much fuel your furnace will burn — those depend on the actual temperature, and wind does not lower it.
Water will not freeze faster than 0 °C no matter how hard the wind blows.
So use wind chill for deciding what to wear and how long to stay out, and the actual temperature for everything mechanical.
The 2001 formula replaced a much older one
The original wind chill index came from Siple and Passel's 1945 Antarctic work, which measured how fast water froze in plastic cylinders. It produced numbers that were dramatic but not physiological.
Canada and the United States jointly adopted the current formula in 2001, based on a trial in which volunteers walked in a refrigerated wind tunnel with thermal transducers on their faces. It models heat loss from exposed skin on a human face at 10 metres of walking pace, using wind measured at the standard anemometer height.
The new formula gives noticeably less extreme numbers than the old one, which is why historical wind chill figures are not comparable with modern ones.
Canada reports the result in degrees Celsius without a degree symbol on broadcast, precisely to signal that it is an index rather than a measurement.
Why it stops at 10 °C and 4.8 km/h
The formula is a regression fitted to trial data within a specific range, and outside that range it produces meaningless output.
Above 10 °C there is no meaningful wind chill — moving air feels pleasant rather than dangerous, and the physiology the formula models does not apply. Below 4.8 km/h the air is effectively still, and the formula would actually return a value warmer than the air temperature.
Environment Canada simply does not report a wind chill outside those bounds, and neither does this calculator.
If it is warm and humid rather than cold and windy, the humidex is the Canadian index you want instead.
Frostbite times assume dry, healthy, unprotected skin
The exposure times in the hazard chart are a useful planning tool but they describe a specific case: a healthy adult, dry skin, no wind protection on the exposed area.
Wet skin freezes dramatically faster, which is why sweat under a scarf or a damp glove liner is more dangerous than it feels. Children lose heat faster because of their surface-area-to-mass ratio. Circulatory conditions, some medications, alcohol and fatigue all shorten the time considerably.
At −40 the difference between the chart and reality can be the difference between a cold walk and a hospital visit.
Treat the chart as a ceiling on safe exposure rather than a target.
The formula
One equation, valid within a defined range.
W = 13.12 + 0.6215·Ta − 11.37·V^0.16 + 0.3965·Ta·V^0.16Ta = air temperature in °CV = wind speed in km/h at the standard 10 m anemometer heightvalid only for Ta ≤ 10 °C and V ≥ 4.8 km/hfrostbite risk on exposed skin (ECCC hazard chart):−10 to −27 low, uncomfortable−28 to −39 increasing, 10 to 30 minutes−40 to −47 high, 5 to 10 minutes−48 to −54 very high, 2 to 5 minutes−55 and below extreme, under 2 minutesreported as a whole number, with no degree symbol
The V^0.16 exponent is what makes wind chill flatten out at higher wind speeds. Going from 10 to 20 km/h changes the index far more than going from 50 to 60 km/h, because the heat-loss benefit of extra wind saturates.
Wind speed must be at the 10 m standard height. Speed at head height is typically lower, which is one reason the index can feel pessimistic in a sheltered street and optimistic on an exposed ridge.
Worked example: a cold Prairie morning
An air temperature of −20 °C with a 30 km/h wind.
- V^0.16 = 30^0.161.7232
- 13.12 + 0.6215 × (−20)0.690
- − 11.37 × 1.7232−19.593
- + 0.3965 × (−20) × 1.7232−13.665
- Wind chill index−33
- Frostbite riskIncreasing — 10 to 30 minutes
−33, matching the published Environment Canada table for those conditions.
The air is still −20 °C. Exposed skin loses heat as though it were −33 in still air, which is what the index is describing.
Dressing for the index
- Cover every exposed area — the index applies to skin, and skin only
- Keep skin dry; wet skin freezes far faster than the chart suggests
- Layer rather than bulk up, so you can shed heat before you sweat
- Check face, ears, fingers and toes regularly — frostbite is painless as it starts
- Wind protection matters more than insulation thickness in high wind
Terms on this page
- Wind chill index
- An equivalent still-air temperature describing the rate of heat loss from exposed skin. Not a measurement of air temperature.
- Anemometer height
- The 10 metre standard height at which wind speed is measured for the formula. Wind at head height is usually slower.
- Siple-Passel index
- The 1945 wind chill formula replaced in 2001. It gave more extreme figures, so historical values are not comparable with modern ones.
- Frostbite
- Freezing of skin and underlying tissue. It begins painlessly, which is why timed checks matter more than how it feels.
Common questions
How is wind chill calculated in Canada?
Wind chill = 13.12 + 0.6215 × Ta − 11.37 × V^0.16 + 0.3965 × Ta × V^0.16, with temperature in °C and wind in km/h. Canada and the United States adopted this formula jointly in 2001.
Does wind chill make things freeze faster?
It makes them reach the air temperature faster, but not go below it. Water will not freeze faster than 0 °C however hard the wind blows. Wind chill describes heat loss from skin, not a lower actual temperature.
Why is there no wind chill above 10 °C?
Because the formula is fitted to trial data within a defined range and produces meaningless results outside it. Environment Canada does not report a wind chill above 10 °C or below 4.8 km/h of wind.
How long before frostbite sets in?
At −28 to −39 exposed skin can freeze in 10 to 30 minutes; at −40 to −47 in 5 to 10; below −55 in under 2. Those assume dry skin on a healthy adult — wet skin, children and circulatory conditions all shorten it considerably.
Why does the wind chill differ from the American figure?
It should not — Canada and the US use the same formula, though the US reports in Fahrenheit with wind in mph. Older figures will differ, because the pre-2001 Siple-Passel index gave more extreme numbers.
Where these numbers come from
- Environment and Climate Change Canada — Wind chill index The official formula, the validity range, and the frostbite hazard chart.
Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
Related calculators
Humidex
Canada's own heat index, from temperature and either dewpoint or relative humidity.
Open calculatorSnowboard size
Board length from weight, height, boot size and riding style — an actual calculator, not a chart.
Open calculatorCubic yards
Concrete, soil and gravel volume in cubic yards and cubic metres — the two units Canadian suppliers actually use.
Open calculator✨ Everyday and leisure calculators
The small calculations that come up in a kitchen, a supermarket aisle or a games session.
See all 10 calculators in this section