Wind chill calculator
How much colder frost feels in wind — by the meteorological services' formula.
Fill in the fields and the result will appear here automatically.
Estimate wind chill with the rounded metric formula using air temperature and wind in km/h. The index describes a heat-loss model, not a new air temperature or a particular person’s or object’s temperature.
How it works
Formula and logic
WC=13.12+0.6215 t −11.37 v^0.16+0.3965 t·v^0.16, t in °C,v in km/h. Difference=WC −t; °F=1.8 WC+32. Increasing wind is not a linear increase in the effect, since the exponent is 0.16.
Example
For −10 °C and 20 km/h: WC≈−17.861 °C and difference≈−7.861 °C. At the product boundaries 10 °C and 4.8 km/h it returns≈9.817 °C. These values do not mean an object cools to WC.
Fields and units
- Air temperature — °C
- Wind speed — km/h
How to use
- — Convert m/s to km/h by multiplying by 3.6.
- — Compare wind measured at the same height; the original model uses standard 10 m wind.
- — For actual risk use weather-service warnings, not the index alone.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- NWS: exposed-skin model and °F/mph bounds
- Limitation
- Preserved product bounds: t≤10 °C,v≥4.8 km/h and t above absolute zero.4.8 km/h is rounded, not the exact 3 mph conversion (4.828032 km/h); NWS specifies wind above 3 mph. The index does not predict frostbite time, clothing or individual tolerance.
FAQ
Does wind actually lower the temperature?
No. The thermometer reads the same at any wind speed. Wind strips the warmed layer of air from the skin so the body loses heat faster — what changes is the rate of heat loss, not the air temperature.
Why does it decline at +15 °C?
Preserved product bounds: t≤10 °C,v≥4.8 km/h and t above absolute zero.4.8 km/h is rounded, not the exact 3 mph conversion (4.828032 km/h); NWS specifies wind above 3 mph. The index does not predict frostbite time, clothing or individual tolerance.
Will a car freeze harder in wind?
Estimate wind chill with the rounded metric formula using air temperature and wind in km/h. The index describes a heat-loss model, not a new air temperature or a particular person’s or object’s temperature. Wind alone does not cool an object below the air; evaporation and radiation are different mechanisms not included here.
Why do some services quote a different number?
Weather services may differ in formula, thresholds, measurement height, units or rounding. Compare identical input conditions; the age of a formula alone does not explain every difference.