What is the formula to convert Celsius to Fahrenheit?

°F = (°C × 9/5) + 32. Multiply the Celsius value by 1.8, then add 32. For example, 25°C becomes (25 × 1.8) + 32 = 45 + 32 = 77°F.

What is 37 degrees Celsius in Fahrenheit?

37°C is 98.6°F. This is normal human body temperature. Using the formula: (37 × 1.8) + 32 = 66.6 + 32 = 98.6°F. A fever is generally considered to be above 38°C (100.4°F).

At what temperature are Celsius and Fahrenheit the same?

At −40 degrees. Both −40°C and −40°F are the same temperature. This is the only point where the two scales intersect. You can verify it: (−40 × 1.8) + 32 = −72 + 32 = −40°F.

How do I convert Fahrenheit to Celsius in my head?

For a quick mental estimate, subtract 30 and halve the result. For 70°F: 70 − 30 = 40, 40 ÷ 2 = 20°C. The exact answer is 21.1°C, so this approximation is accurate to within a couple of degrees for typical weather temperatures.

Celsius to Fahrenheit: How Temperature Conversion Really Works

Celsius to Fahrenheit Conversion: The Formula and Quick Examples

To convert Celsius to Fahrenheit, use this formula: °F = (°C × 9/5) + 32. That's it. Multiply the Celsius temperature by 1.8 (which is 9 divided by 5), then add 32. Here are three worked examples:

20°C → (20 × 1.8) + 32 = 36 + 32 = 68°F
100°C → (100 × 1.8) + 32 = 180 + 32 = 212°F
−10°C → (−10 × 1.8) + 32 = −18 + 32 = 14°F

The formula works for any temperature including negatives. For quick conversions without doing the arithmetic, use the free unit converter at allio.tools.

Converting Fahrenheit to Celsius: The Reverse Formula

To go the other direction — Fahrenheit to Celsius — the reverse formula is: °C = (°F − 32) × 5/9. Subtract 32 first, then multiply by 0.556 (or divide by 1.8). Examples:

98.6°F → (98.6 − 32) × 5/9 = 66.6 × 0.556 = 37°C (normal body temperature)
350°F → (350 − 32) × 5/9 = 318 × 0.556 = 176.7°C
32°F → (32 − 32) × 5/9 = 0 × 0.556 = 0°C (freezing point of water)

The order of operations matters: always subtract 32 before multiplying. Getting that backwards is the most common mental arithmetic mistake.

5 Temperature Benchmarks Worth Memorising

Rather than converting every time, memorise these anchor points and you can estimate most temperatures at a glance:

0°C / 32°F — water freezes; roads may ice over
20°C / 68°F — a comfortable room temperature
37°C / 98.6°F — healthy human body temperature
100°C / 212°F — water boils at sea level
−40°C / −40°F — the one point where both scales agree exactly

With these five anchors, you can sanity-check any conversion. If someone tells you it's 50°F outside, you know it's between 10°C and 20°C — cool but not cold. If a recipe says 400°F, you know it's roughly 200°C — a hot oven.

Why Does the US Still Use Fahrenheit?

Most of the world switched to Celsius as part of adopting the metric system during the 19th and 20th centuries. The United States, along with a small handful of other countries, did not make that transition for everyday use. Fahrenheit was proposed in 1724 by Daniel Fahrenheit, who calibrated his scale using a brine mixture (0°F), ice water (32°F), and human body temperature (96°F in his original scale, later adjusted to 98.6°F).

The practical argument in favour of Fahrenheit for weather reporting is that its 0–100 range roughly maps to the range of temperatures humans experience outdoors in temperate climates — so "it's 72 out" feels intuitive. Celsius defenders counter that the scale is simpler mathematically. Both arguments are mostly habit at this point.

Temperature in Cooking: Common Oven Temperatures in Both Scales

Recipes from different countries use different scales, which causes real confusion. Here are the most common oven temperature settings:

150°C / 300°F — low / slow cook (meringues, slow-roasted meat)
180°C / 350°F — moderate oven (most cakes, biscuits, roast chicken)
200°C / 400°F — moderately hot (bread, vegetables, pastry)
220°C / 425°F — hot oven (pizza, quick-roast potatoes, puff pastry)
240°C / 475°F — very hot (Neapolitan pizza, searing steaks briefly)

Fan-assisted ovens typically run 15–20°C hotter than stated for a conventional setting, so reduce the temperature accordingly when converting between oven types.

Temperature in Weather: Reading International Forecasts

If you're travelling internationally or reading a weather app set to the wrong scale, knowing a few reference points prevents confusion. A summer forecast of 35°C is hot — that's 95°F. A mild spring day at 15°C is 59°F — light jacket territory. A winter morning at −5°C is 23°F — genuinely cold, frost likely.

A quick mental shortcut for rough Celsius-to-Fahrenheit conversion: double the Celsius temperature and add 30. This is an approximation (the true addition is 32, and the multiplier is 1.8 not 2), but it's accurate enough for weather estimates. For 20°C: (20 × 2) + 30 = 70°F. The actual answer is 68°F — close enough for deciding what to wear.

Beyond Celsius and Fahrenheit: Kelvin and Rankine

Science uses two additional temperature scales. Kelvin (K) is the SI unit of temperature and starts at absolute zero — the theoretical point where molecular motion stops (−273.15°C / −459.67°F). Converting from Celsius to Kelvin is simple: add 273.15. So 0°C = 273.15K and 100°C = 373.15K. Kelvin has no degree symbol — you write 300K, not 300°K.

Rankine (°R) is the Fahrenheit-based absolute scale, used in some US engineering contexts. It equals Fahrenheit + 459.67. The unit converter at allio.tools handles all four scales — useful if you encounter Kelvin or Rankine in scientific or engineering contexts.