Wind Chill Calculator
Feels like temperature from air temp and wind speed, with frostbite guidance in F and C.
What it does
Wind chill translates thermometer air plus wind into the temperature skin feels. Moving air strips the thin warm layer the body heats, so exposed cheeks cool toward a lower effective temperature than the station reports.
The tool above runs the official joint US and Canadian index in both systems. Enter air temperature with steady wind speed and read the feels like value with a frostbite guide beside it.
The default of 20 F at 15 mph feels like 6 F, cold enough to cover up but shy of fast frostbite. At 0 F with the same wind the index drops to -19 F, where uncovered skin can freeze within 30 minutes.
The formula comes from human trials run for the National Weather Service with the Canadian service adopting the same index. Both define it only for cold air with real wind: calm cold feels like the thermometer says.
How to use
- Pick imperial (F, mph) or metric (C, km/h).
- Enter the station air temperature, not a car sensor in sun.
- Enter steady wind speed, not gusts.
- Read feels like first for clothing choices.
- Read the frostbite guide before long exposure.
Formula
- T
- Air temperature: F in the US form, C in the Canadian form.
- V
- Wind speed: mph in the US form, km/h at 10 m in the Canadian form.
- 0.16
- Wind exponent fitted to the human trial data.
Valid at or below 50 F (10 C) with wind above 3 mph (near 5 km/h). Results round to whole degrees. Gusts spike the instant value above the steady wind result shown here.
Worked example
Example: 20 F with 15 mph wind
Imperial defaults: air 20 F, wind 15 mph.
- Wind term: 15^0.16 = 1.5424.
- Base: 35.74 + 0.6215 x 20 = 48.17.
- Wind parts: 35.75 x 1.5424 = 55.14 and 0.4275 x 20 x 1.5424 = 13.19.
- Combine: 48.17 - 55.14 + 13.19 = 6.2, rounds to 6 F (-14 C).
- Risk: 6 sits in 0 to 32, cold with frostbite possible after 30 minutes.
- Tool shows 6 F, the cold guide, and Air 20 F at 15 mph.
Reference table
| Air | Wind | Feels like |
|---|---|---|
| 32 F | 10 mph | 24 F |
| 20 F | 15 mph | 6 F |
| 0 F | 15 mph | -19 F |
| 0 F | 30 mph | -26 F |
| -6.7 C | 24 km/h | -14 C |
Limits
- Cold air only: above 50 F the index has no meaning.
- Needs real wind: calm air feels like the thermometer.
- Open ground exposure assumed; shelter cuts the effect.
- Clothing, sun, and wet skin shift comfort around the number.
Common mistakes
- Running the formula on mild days and quoting a colder feel.
- Feeding gusts instead of steady wind.
- Reading car sensors parked in sun as air temperature.
- Mixing mph with the Celsius constants.
- Treating the index as a thermometer reading objects also feel.
Try it yourself
Quick checks. Answers sit tucked under each question.
0 F at 15 mph?
-19 F: very cold, frostbite can start within 30 minutes.
Metric defaults -6.7 C at 24 km/h?
-14 C, the same air as the 6 F example.
Calm 20 F at 2 mph?
Rejected: the tool asks for wind between 4 and 110 mph.
Questions
What is the wind chill formula?
In F and mph: 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16).
When does wind chill apply?
At or below 50 F with wind above 3 mph. Calm cold just feels like the thermometer.
Can frostbite hit above freezing air?
No. Air itself must sit below freezing for skin to freeze, though wind speeds the path there.
Why does wind make it feel colder?
It strips the warm boundary layer off skin, raising heat loss at the same air temperature.
Is the Canadian formula different?
Same index in C and km/h: 13.12 + 0.6215T - 11.37(V^0.16) + 0.3965T(V^0.16).
What should I wear at 6 F feels like?
Hat, gloves, windproof shell, and covered face for long stays. Keep extremities dry.