Fahrenheit to Celsius

How Fahrenheit ↔ Celsius conversion works

Temperature scales are linear but offset: freezing and boiling of water sit at different numbers on °F and °C. Converting is not a simple multiply by a constant without an offset — you must subtract or add 32 at the right step. That is the most common source of mental-math errors when traveling or following a recipe from another country.

In the UK and most of Europe, weather, ovens, and thermostats use Celsius. Fahrenheit remains common in the United States. Mixing a US recipe’s oven setting with a European oven (or the reverse) without converting can undercook or overheat food by a large margin.

Formulas (both directions)

• Fahrenheit → Celsius: °C = (°F − 32) × 5/9
• Celsius → Fahrenheit: °F = °C × 9/5 + 32
• Kelvin (not on this page): K = °C + 273.15

Reference points at standard pressure: water freezes at 32°F = 0°C and boils at 212°F = 100°C. Room comfort often sits near 68–72°F (20–22°C). The scales meet at −40° (−40°F = −40°C), which is a useful memory check for the formula.

Worked examples: °F to °C

Worked examples: °C to °F

Weather quick reference

Oven conversion notes

US recipes often list °F; UK/EU recipes often list °C (and sometimes gas marks). Convert the number before you set the dial. Fan (convection) ovens may recommend a lower set temperature than conventional ovens for the same recipe — that adjustment is separate from °F↔°C conversion. Always follow your oven’s manual when fan mode is involved.

If a recipe says “moderate oven” without a number, check a trusted chart for your country rather than guessing. When two charts disagree by 5–10°C, prefer the recipe author’s region and watch the dish for the first bake instead of trusting a single conversion blindly.

When each scale is used

• Celsius — UK and European weather, most scientific work, EU oven recipes, and metric thermostats.
• Fahrenheit — US weather, many US household thermostats, and US cookbook oven settings.
• Kelvin — Science and engineering absolute temperature; convert to °C first on this page, then add 273.15.

Practical scenarios

Travel packing. A forecast of 12°C is 53.6°F — cool enough for a jacket for many people — while 28°C is 82.4°F. Convert the destination’s usual scale before you pack, especially when switching between UK/EU Celsius forecasts and US Fahrenheit apps.

Following a foreign recipe. A US cookie recipe at 350°F is about 177°C. A UK recipe at 180°C is about 356°F. Convert before preheating. If your oven only shows gas marks, use the oven manufacturer’s chart after you have °C or °F — gas marks are not a third independent temperature scale you can derive from this page alone.

Classroom science. Lab work almost always uses Celsius or kelvin. Convert any Fahrenheit givens to °C with the exact formula, then proceed. The −40 meeting point is a useful sanity check when students test both directions.

Shared thermostats. When two people share a thermostat — one used to °F and one used to °C — agree on a single display unit. Converting a preferred comfort band once (for example 20–22°C ↔ 68–72°F) avoids daily mix-ups and accidental overnight setbacks.

How to use it

1. Enter a temperature in °F or °C.
2. Read the linked field for the other scale.
3. For cooking, double-check whether the recipe author’s country uses Fahrenheit ovens.
4. For weather packing, convert the forecast unit you will actually see at the destination.

Common mistakes

• Multiplying by 5/9 without subtracting 32 first (or the reverse when going to °F).
• Assuming “feels like” / wind chill equals air temperature — those indexes are different.
• Confusing oven gas marks with °C/°F without a chart for your oven model.
• Using the rough “subtract 30 and halve” trick for baking or medicine — it is only for ballpark weather chat.

Decision checklist

• Is this air temperature or oven temperature? → Same formula; different safe ranges.
• Is the number already a “feels like” index? → Do not treat it as raw °C/°F from a thermometer.
• Do I need kelvin? → Get °C here, then add 273.15.
• Is body temperature involved? → Use clinical guidance; individual normals vary.

Frequently asked questions

Quick estimate without a calculator?

A rough °C ≈ (°F − 30) / 2 trick is only for ballpark weather chat — use the exact formula for cooking or medicine.

What about kelvin?

Kelvin = °C + 273.15. This page does not convert to kelvin; add 273.15 after you have Celsius if you need SI absolute temperature.

Why do fever apps show 98.6°F and 37°C?

37°C converts to 98.6°F with the standard formula. Individual normal body temperature varies; follow clinical guidance rather than a single classic number. This site does not provide medical advice.

Limitations

Does not convert to kelvin. Weather “feels like” indexes are not the same as air temperature. See also the metric and imperial conversions guide.