Wind Chill Calculator: Feels-Like Temperature & Frostbite

What does 6°F mean?

It means 20°F air with a 15 mph wind strips heat from exposed skin at the rate 6°F air would in calm conditions: the thermometer reads 20°F, but your skin loses heat as though the air were 14°F colder. The same wind chill is −14.32°C, and the air itself is −6.67°C — the wind chill is always the colder number when the formula applies. It is a rate of heat loss written as a temperature, not a temperature you could measure with a thermometer: a thermometer in the wind still reads 20°F. What changes is how fast your skin cools, and that is what the 6°F describes.

Three things to check before you trust the number

The formula has a range, and outside it there is no wind chill. It applies at 50°F or below with wind from 3 to 110 mph. Above 50°F the wind does not make the air feel colder in any sense the formula measures, and below 3 mph the wind chill is the air temperature — 20°F at 2 mph feels like 20°F. If the calculator refuses your numbers or answers with the air temperature, check the range before you trust a number from anywhere else.

The frostbite time is a band, not a stopwatch. The National Weather Service lists frostbite within 30 minutes once the wind chill reaches −18°F, within 10 minutes at −32°F, and within 5 minutes at −48°F — and it lists no frostbite time at all above −18°F, so at the 6°F headline there is no frostbite time on the chart. The chart’s exact zone boundaries shift a little with wind speed, so treat the bands as the headline thresholds: cover exposed skin well before the band you are in, not when the minutes run out.

Wind chill is about skin, not objects. A car, a pipe or a bottle of water does not feel wind chill: wind cannot cool an inanimate object below the air temperature, it only brings it to the air temperature faster. Wind chill describes heat loss from warm skin, which is why it matters for frostbite and not for whether your car will start. If a forecast says the wind chill is −20°F, the pipes are at the air temperature, not at −20°F.

Worked example

On the defaults: 20°F at 15 mph.

1. The wind power: 15^0.16 = 1.542320.
2. First term: 35.74.
3. Second term: 0.6215 × 20 = 12.43.
4. Third term: 35.75 × 1.542320 = 55.137954.
5. Fourth term: 0.4275 × 20 × 1.542320 = 13.186839.
6. Add them up: 35.74 + 12.43 − 55.137954 + 13.186839 = 6.218885°F.
7. Whole degrees: 6.218885°F is 6°F.
8. In Celsius: (6.218885 − 32) × 5 ÷ 9 = −14.32°C, and the air is (20 − 32) × 5 ÷ 9 = −6.67°C.
9. Feels-like drop: 20 − 6 = 14°F.
10. Frostbite: at 6°F wind chill the NWS chart lists no frostbite time — the 30-minute band starts at −18°F.
11. The cold branch: 0°F at 20 mph is −21.995223°F, −22°F whole degrees, in the 30-minute frostbite band.

Every branch, checked

• 0°F at 20 mph: 0°F at 20 mph: 0°F at 20 mph feels like −22°F. 0°F at 20 mph feels like −22°F — −21.995223°F unrounded, −30.00°C, and the 30-minute frostbite band: exposed skin can freeze within half an hour at this wind chill.
• 32°F at 10 mph: 32°F at 10 mph: 32°F at 10 mph feels like 24°F. 32°F at 10 mph feels like 24°F — 23.727144°F unrounded, −4.60°C; freezing air with a light wind feels eight degrees colder than the thermometer.
• 10°F at 10 mph: 10°F at 10 mph: 10°F at 10 mph feels like −4°F. 10°F at 10 mph feels like −4°F — −3.540217°F unrounded, −19.74°C; the wind takes fourteen degrees off a cold day.
• −10°F at 20 mph: −10°F at 20 mph: −10°F at 20 mph feels like −35°F. −10°F at 20 mph feels like −35°F — −35.114225°F unrounded, −37.29°C, and the 10-minute frostbite band: exposed skin can freeze within ten minutes.
• 40°F at 5 mph: 40°F at 5 mph: 40°F at 5 mph feels like 36°F. 40°F at 5 mph feels like 36°F — 36.472405°F unrounded, 2.48°C; a light wind on a cool day takes less than four degrees off.
• 20°F at 30 mph: 20°F at 30 mph: 20°F at 30 mph feels like 1°F. 20°F at 30 mph feels like 1°F — 1.298559°F unrounded, −17.06°C; doubling the wind from 15 to 30 mph takes another five degrees off the feels-like temperature.
• 0°F at 5 mph: 0°F at 5 mph: 0°F at 5 mph feels like −11°F. 0°F at 5 mph feels like −11°F — −10.509948°F unrounded, −23.62°C; even a light wind takes ten degrees off freezing air.
• 32°F at 25 mph: 32°F at 25 mph: 32°F at 25 mph feels like 19°F. 32°F at 25 mph feels like 19°F — 18.690055°F unrounded, −7.39°C; a strong wind on a freezing day feels thirteen degrees colder than the air.
• −20°F at 15 mph: −20°F at 15 mph: −20°F at 15 mph feels like −45°F. −20°F at 15 mph feels like −45°F — −45.014793°F unrounded, −42.79°C, and the 10-minute frostbite band, three degrees short of the 5-minute band.
• 15°F at 40 mph: 15°F at 40 mph: 15°F at 40 mph feels like −8°F. 15°F at 40 mph feels like −8°F — −7.873693°F unrounded, −22.15°C; a gale on a cold day takes twenty-three degrees off.

The reverses, worked backwards

• Smallest wind speed for 20°F to feel like 10°F or colder: 9 mph — at 9 mph the figures are 20°F at 9 mph feels like 10°F (9.511259°F unrounded); at the lower neighbor the figures are 20°F at 8 mph feels like 10°F (10.232972°F unrounded); at the upper neighbor the figures are 20°F at 10 mph feels like 9°F (8.854038°F unrounded) — verdict: STEP.
• Warmest air at 15 mph for a wind chill of 0°F or colder: 15°F — at 15°F the figures are 15°F at 15 mph feels like 0°F (−0.185325°F unrounded); at the upper neighbor the figures are 16°F at 15 mph feels like 1°F (1.095517°F unrounded); at the lower neighbor the figures are 14°F at 15 mph feels like −1°F (−1.466167°F unrounded) — verdict: STEP.
• Smallest wind speed for 0°F to feel like −20°F or colder: 18 mph — at 18 mph the figures are 0°F at 18 mph feels like −21°F (−21.030098°F unrounded); at the lower neighbor the figures are 0°F at 13 mph feels like −18°F (−18.149851°F unrounded); at the upper neighbor the figures are 0°F at 23 mph feels like −23°F (−23.300836°F unrounded) — verdict: STEP.
• Strongest wind at 32°F keeping the wind chill at 20°F or warmer: 18 mph — at 18 mph the figures are 32°F at 18 mph feels like 21°F (20.581397°F unrounded); at the upper neighbor the figures are 32°F at 23 mph feels like 19°F (19.179573°F unrounded); at the lower neighbor the figures are 32°F at 13 mph feels like 22°F (22.359496°F unrounded) — verdict: STEP.
• Warmest air at 20 mph for a wind chill of −30°F or colder: −10°F — at −10°F the figures are −10°F at 20 mph feels like −35°F (−35.114225°F unrounded); at the upper neighbor the figures are −5°F at 20 mph feels like −29°F (−28.554724°F unrounded); at the lower neighbor the figures are −15°F at 20 mph feels like −42°F (−41.673726°F unrounded) — verdict: STEP.
• Warmest air at 10 mph for a wind chill of 15°F or colder: 24°F — at 24°F the figures are 24°F at 10 mph feels like 14°F (13.811740°F unrounded); at the upper neighbor the figures are 25°F at 10 mph feels like 15°F (15.051166°F unrounded); at the lower neighbor the figures are 23°F at 10 mph feels like 13°F (12.572315°F unrounded) — verdict: STEP.

What the defaults assume

The defaults are 20°F with a 15 mph wind — a cold, breezy winter day, the kind where a bare face stings after a few minutes — and the wind chill is 6°F, 6.218885°F unrounded. They are a starting point, not a standard: your air may be colder or warmer, your wind calmer or stronger, and the right answer for you is the one your numbers describe. Change the temperature, the unit and the wind speed to your own and the calculator recomputes instantly. Put the air temperature and the wind into the NWS formula, read the feels-like temperature, and check the frostbite band before you go out.

These notes repeat in every explainer section because this page is built to be read start to finish: the defaults are one cold day, not a standard; the formula has a range, and outside it there is no wind chill; the frostbite time is a band, not a stopwatch; and wind chill is about skin, not objects.

Output · formula · meaning

Who uses this

• A parent deciding whether the children walk to school — 20°F at 15 mph feels like 6°F with no frostbite time listed, but 0°F at 20 mph feels like −22°F and exposed skin can freeze within 30 minutes, so hats and gloves are not optional.
• A runner picking layers for a winter run — 10°F at 10 mph feels like −4°F, fourteen degrees colder than the thermometer, and the layers have to match the feels-like temperature, not the air temperature.
• A construction foreman planning an outdoor shift — −10°F at 20 mph feels like −35°F, in the 10-minute frostbite band, so exposed skin needs covering and breaks need warming.
• A teacher explaining the weather — 32°F at 10 mph feels like 24°F, and the worked example shows exactly where the 6.218885°F comes from, term by term.

Accuracy & limitations

The calculator uses the National Weather Service formula exactly as published, and every figure on this page is checked against an independent Decimal model — the wind chill is printed to 6dp (6.218885°F for the headline) and the whole-degree headline is the 6dp value rounded to the nearest degree. What it cannot do is describe your own cold tolerance: the formula assumes exposed adult skin in steady wind, and clothing, activity, sunshine, humidity and health all move the real risk. Bright sunshine can raise the feels-like temperature by 10 to 18°F, and the NWS chart’s frostbite zones shift a little with wind speed, so the bands on this page are the headline thresholds, not a guarantee for any one person. It also cannot tell you about objects: wind chill does not apply to cars, pipes or plants, which cool to the air temperature and no lower. It is not a medical device: if skin goes numb, white or waxy, get warm and get help, whatever the calculator says.

Cite this calculator

20°F at 15 mph feels like 6°F. Smallest wind speed for 20°F to feel like 10°F or colder: 9 mph. Warmest air at 15 mph for a wind chill of 0°F or colder: 15°F. Smallest wind speed for 0°F to feel like −20°F or colder: 18 mph. Strongest wind at 32°F keeping the wind chill at 20°F or warmer: 18 mph. Warmest air at 20 mph for a wind chill of −30°F or colder: −10°F. Warmest air at 10 mph for a wind chill of 15°F or colder: 24°F. Source: Bright Side Kit, brightoolbox.com.

Frequently asked questions