Calculate wind chill with the official 2001 NWS wind chill formula — plus a frostbite-time chart, Canadian metric mode, reverse mode (feels-like to actual temperature), and a cold-weather clothing guide. A feels like temperature calculator that runs 100% in your browser — no wind chill app to install, nothing uploaded.
Planning aid: wind chill estimates how cold exposed skin feels.
Always follow official NWS warnings and advisories for your area before heading out.
Not what you're looking for? Wind chill only applies at
50°F (10°C) and below — it cannot tell you how hot it feels.
For hot, humid weather use our heat index calculator,
the warm-weather half of the “feels like” suite.
Wind chill calculator
Enter the air temperature and wind speed. Uses the official
2001 NWS formula (°F/mph) or the Environment Canada metric formula (°C/km/h) —
the two published forms of the same human-trials model.
Wind chill is defined only for temperatures at or below 50°F (10°C)
and winds above 3 mph (4.8 km/h). Below the calm threshold the air simply feels like the thermometer reads.
Wind chill & frostbite chart
The full NWS wind chill chart — a wind chill temperature chart and
feels like temperature chart for winter — computed live from the official formula.
Cell colors show the frostbite indicator: how long exposed skin can last before frostbite develops.
Frostbite-time bands follow the NWS Wind Chill Chart frostbite indicator
(Defence R&D Canada data): −27 to −39°C → 10–30 min;
−40 to −47°C → 5–10 min; −48 to −54°C → 2–5 min;
below −55°C → under 2 min. Frostbite needs the actual air temperature below
freezing — wind chill alone above 32°F cannot freeze skin.
Reverse: from feels-like to actual temperature
Heard the wind chill on the forecast and want the real thermometer reading?
Enter the feels-like temperature and wind speed — solved exactly from the formula (no guessing).
What is wind chill?
Wind chill is the temperature your exposed skin feels when cold air and wind combine.
The wind chill meaning is simple: it translates the thermometer reading plus wind speed into
the temperature your skin actually experiences. Wind strips away the thin layer of warm
air your body heats around itself, so heat leaves your skin
faster — the stronger the wind, the colder it feels, even though the thermometer hasn't moved.
The number comes from the 2001 NWS/Environment Canada index, built from human facial-cooling trials
in wind tunnels (it replaced the 1945 Siple–Passel index).
NWS formula: WC = 35.74 + 0.6215T − 35.75V0.16 + 0.4275TV0.16
(T in °F, V in mph). Metric (Environment Canada):
W = 13.12 + 0.6215T − 11.37V0.16 + 0.3965TV0.16 (T in °C, V in km/h).
What is wind chill?Wind chill is the temperature your exposed skin feels when cold air and wind combine — the winter version of a “feels like” temperature. Wind strips away the thin layer of warm air your body heats around itself, so heat leaves your skin faster and it feels colder than the thermometer reads. Worked example: at 0°F with a 15 mph wind, the official NWS wind chill is −19°F — exposed skin feels −19°F and can freeze in about 30 minutes. This wind chill calculator uses the 2001 NWS wind chill formula, the same one behind every US forecast.
What is the wind chill formula?The NWS wind chill formula is WC = 35.74 + 0.6215T − 35.75V⁰·¹⁶ + 0.4275TV⁰·¹⁶, with T in °F and V in mph. The metric version (Environment Canada) is W = 13.12 + 0.6215T − 11.37V⁰·¹⁶ + 0.3965TV⁰·¹⁶, with T in °C and V in km/h. Both are the two published forms of the same 2001 human-trials model — use the wind chill fahrenheit form for US forecasts and the wind chill celsius form for metric countries. The formula is only defined for temperatures at or below 50°F (10°C) and wind speeds above 3 mph (4.8 km/h).
Wind chill calculation example: 10°F with a 25 mph wind?Plug T = 10 and V = 25 into the NWS formula. First 25⁰·¹⁶ ≈ 1.6737. Then WC = 35.74 + 6.215 − 59.834 + 7.155 = −10.7°F. So a 10°F morning with a 25 mph wind feels like −10.7°F — 20.7°F colder than the thermometer reads. Try it in the calculator above; the chart tab shows the same cell computed live.
Does humidity affect wind chill?Practically no. If you searched for wind chill with humidity, here is the short answer: when the NWS tested the new wind chill index, relative humidity changed the result by less than 1°F, so humidity was left out of the formula entirely. Humidity matters for the heat index on hot days, not for wind chill — you can ignore the humidity reading on a cold day. Note: being wet still chills you faster through direct heat loss; that is separate from the wind chill number.
Wind chill vs actual temperature — how are they related?They are linked by the same formula, solved backwards. Example: the forecast says it feels like −20°F with a 20 mph wind — the actual air temperature is about 1.5°F, so the wind makes it feel 21.5°F colder. Use the Reverse tab above: enter any feels-like temperature and wind speed to recover the thermometer reading exactly. It is an algebraic inversion of the formula, not an approximation.
What is the wind chill on a motorcycle?Your speed becomes the wind. At 32°F riding at 50 mph on a calm day, the wind chill is 14.4°F — it feels 17.6°F colder than the air temperature. That is why a mild 40s day can bite hard on a bike. Use the rider presets above (30, 50, 70 mph), and add any headwind to your speed for the true effective wind. Full face coverage matters: at highway speeds frostbite times shrink fast.
How do I calculate wind chill in Celsius?Use the Environment Canada metric formula: W = 13.12 + 0.6215T − 11.37V⁰·¹⁶ + 0.3965TV⁰·¹⁶ with T in °C and V in km/h. Example: −20°C with a 30 km/h wind gives −32.6°C. For very light winds under 5 km/h, Environment Canada uses a second formula, W = T + ((−1.59 + 0.1345T)/5) × V — the calculator applies it automatically when it applies. Traveling? The metric mode also handles wind chill UK winter forecasts and wind chill Australia alpine conditions, anywhere temperatures are reported in °C.
How fast can frostbite set in? (frostbite time chart)It depends on the wind chill, following the NWS Wind Chill Chart frostbite indicator: above −27°C (−17°F), low risk; −27 to −39°C, exposed skin can freeze in about 10–30 minutes; −40 to −47°C, about 5–10 minutes; −48 to −54°C, about 2–5 minutes; below −55°C (−67°F), under 2 minutes. The chart tab colors every cell by these bands, and the main calculator shows your zone with clothing advice.
When is wind chill not defined?Wind chill is not defined above 50°F (10°C) or at wind speeds of 3 mph (4.8 km/h) or less — in those cases the air simply feels like the thermometer reads. It also applies only to living skin: wind chill cannot cool an object below the actual air temperature. The NWS example: with −5°F air and a −31°F wind chill, your car radiator will not drop below −5°F — wind only gets it there faster.
How cold is too cold to go outside?Watch the frostbite time, not just the temperature. Once the wind chill pushes frostbite under about 30 minutes (for example 0°F with a 15 mph wind → −19°F), cover all exposed skin and limit continuous time outside. Under about 10 minutes, avoid non-essential exposure. NWS offices set local warning criteria — for example, Rochester, NY issues a Cold Weather Advisory at −15 to −24°F wind chill and an Extreme Cold Warning at or below −25°F — so always follow your local NWS office.
Why did the wind chill formula change in 2001?The old 1945 Siple–Passel index was based on how fast water froze in cans in Antarctica — it overstated cooling on living skin. In 2001, US and Canadian scientists ran human facial-cooling trials in wind tunnels and rebuilt the index from heat-transfer theory. The new numbers typically read 10–15°F warmer than the old formula at strong winds, and match what people actually feel.
Is wind chill accurate for children and the elderly?Treat it as a starting point and be more cautious. The NWS trials used adult subjects — for safety reasons no children were tested. Children, the elderly, and anyone with circulation or health issues lose heat faster, so cover their skin sooner and keep exposure well below the frostbite times shown on the chart.
Related calculators
Heat index calculator — the warm-weather half of the “feels like” suite: how hot humid air feels on your skin.
Sources: National Weather Service “Understanding Wind Chill” (weather.gov) —
formula domain, worked example, humidity & inanimate-object notes;
Environment and Climate Change Canada hourly-data technical documentation — metric formulas;
NWS Wind Chill Chart frostbite indicator (Defence R&D Canada data) — frostbite-time bands.
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