Wind Chill Calculator
Enter the air temperature and wind speed. The calculator returns the wind chill — what the cold actually feels like on exposed skin — using the National Weather Service and Environment Canada formula, plus a frostbite risk band.
Wind chill (felt temperature)
-13.0 °C
- Feels colder than air by
- 8.0 °C
- Wind chill in other unit
- 8.6 °F
- Air temperature
- -5.0 °C
- Wind speed
- 30.0 km/h
- Frostbite risk
- Low — Low risk of frostbite. Dress warmly, especially for prolonged exposure.
Wind chill (°C) = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16, where T is the air temperature in °C and V is the wind speed in km/h. The formula was adopted by Environment Canada and the US National Weather Service in November 2001.
How to use this calculator
Choose your unit system (°C with km/h, or °F with mph). Enter the actual outdoor air temperature and the sustained wind speed. The calculator returns the wind chill in both unit systems, the gap between air temperature and felt temperature, and a frostbite risk advisory aligned with Environment Canada bands. Wind chill is meaningful only in the cold — the formula is calibrated for temperatures at or below 10°C (50°F) and wind speeds at or above 4.8 km/h (3 mph). Below that wind threshold the felt temperature equals the air temperature.
How the calculation works
Wind strips heat from exposed skin faster than still air, so the temperature you actually feel is lower than the thermometer reads. The current formula, jointly adopted by the US National Weather Service and Environment Canada in November 2001, models this effect from experimental data on heat loss from the human face. In °C with V in km/h: WC = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16. In °F with V in mph: WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16. T is the air temperature, V is the wind speed and V^0.16 captures the diminishing-returns effect of stronger wind — going from 10 to 20 km/h matters more than going from 60 to 70.
Worked example
Take an air temperature of −5°C and a wind speed of 30 km/h. V^0.16 = 30^0.16 ≈ 1.7232. WC = 13.12 + 0.6215·(−5) − 11.37·1.7232 + 0.3965·(−5)·1.7232 = 13.12 − 3.108 − 19.593 − 3.416 ≈ −13.0°C. So the wind makes −5°C feel like −13°C — a gap of 8 degrees. Environment Canada classes that as a low frostbite risk for short outdoor exposure, but recommends covering exposed skin and dressing in layers for anything longer than an hour.
Frequently asked questions
What is wind chill, exactly?
Wind chill is the temperature your skin "feels" when the wind is blowing — specifically how cold a bare human face perceives the combination of air temperature and wind. It is not the actual air temperature (a thermometer always reads the latter), and it does not change how fast water freezes. It is purely a human-perception quantity, designed to communicate frostbite risk in numbers people already understand.
Why does wind make it feel colder?
Your body keeps itself warm by radiating heat into a thin layer of warm air pressed against your skin. Wind blows that warm boundary layer away and replaces it with fresh cold air, so your body has to keep warming a fresh patch of air over and over. The faster that exchange, the faster heat leaves you, and the colder it feels. Above about 70 km/h the boundary layer is already gone, so extra wind speed makes little additional difference — which is why the formula uses V^0.16 rather than a linear term.
When is the wind chill formula valid?
The 2001 NWS / Environment Canada formula was calibrated for air temperatures of 10°C (50°F) or lower and wind speeds of 4.8 km/h (3 mph) or higher. Below that wind threshold the formula returns the air temperature unchanged — calm air does not create a chilling effect. Above 10°C, "wind chill" is not normally reported (the relevant comfort metric in warmth is heat index or apparent temperature, not wind chill).
Is wind chill the same as "RealFeel" or "apparent temperature"?
No. Wind chill uses only air temperature and wind speed and applies to cold weather. Apparent temperature (used in summer) and proprietary indices like AccuWeather RealFeel combine more variables — humidity, solar radiation, cloud cover — and produce different numbers. For pure wind-driven cold the NWS formula is the standard.
What does the frostbite risk band tell me?
Environment Canada publishes bands relating wind chill in °C to the typical time before frostbite occurs on exposed skin. At about −28°C frostbite becomes possible within 10–30 minutes, at −40°C within 5–10 minutes, at −48°C within 2–5 minutes, and at −55°C or colder within 2 minutes. Risk depends on individuals (children, the elderly and people with circulation issues are more vulnerable), exposure of skin, and clothing — the bands are guidance, not a guarantee.
Why does the answer differ slightly from what my weather app shows?
Most national weather services use the same 2001 formula, but apps may round differently or feed it slightly different inputs — a wind speed measured at a nearby airport, or a 10-minute average versus an instantaneous gust. Differences of one or two degrees are normal. The math here uses the formula directly with the numbers you enter.
Does wind chill matter for anything besides comfort?
Yes — it is the standard tool for issuing cold-weather warnings (Wind Chill Advisory, Warning, and Extreme Cold Warning thresholds are all defined in wind-chill terms in the US and Canada) and for estimating frostbite onset time. It does not change the freezing rate of pipes, vehicle batteries or radiators — those depend on actual air temperature.