Free temperature converter. Convert between Celsius, Fahrenheit and Kelvin instantly using exact formulas, with key reference points included.
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Celsius and Fahrenheit overlap through two anchor points, water freezes at 0°C/32°F and boils at 100°C/212°F. The 100 Celsius degrees between them span 180 Fahrenheit degrees (a 9/5 ratio), plus a 32-degree offset for the different zero points. Kelvin is simply Celsius shifted by 273.15, with no rescaling.
°F = (°C × 9/5) + 32 · °C = (°F − 32) × 5/9 · K = °C + 273.15
Why both a multiplication and an addition? The degree sizes differ AND the zero points differ. The 100 Celsius degrees between water's freezing and boiling points span 180 Fahrenheit degrees, so each Celsius degree is 9/5 (1.8) Fahrenheit degrees, the multiplication. Fahrenheit's zero sits 32 degrees below freezing, the addition.
Worked example: convert 20°C to Fahrenheit. 20 × 9/5 = 36; 36 + 32 = 68°F. Reverse it: (68 − 32) × 5/9 = 36 × 5/9 = 20°C. For Kelvin: 20°C + 273.15 = 293.15 K.
1. Enter your temperature. 2. Choose the unit it is in: Celsius, Fahrenheit or Kelvin. 3. Choose the unit you want.
Results appear instantly to 2 decimal places. The most common conversions are Celsius to Fahrenheit (weather forecasts, recipes) and Fahrenheit to Celsius (US thermostats and thermometers).
Absolute zero: −273.15°C = −459.67°F = 0 K | −40 is the only point where both scales agree | Water freezes: 0°C = 32°F = 273.15 K | Room temperature: 20°C = 68°F = 293.15 K | Body temperature: 37°C = 98.6°F = 310.15 K | Fever threshold: 38°C = 100.4°F | Water boils: 100°C = 212°F = 373.15 K
Memorize freezing, room, body and boiling and you can sanity-check any conversion instantly.
Recipe books from different countries default to different scales, so oven conversion is one of the most common everyday uses. A moderate 350°F oven (classic US setting for cakes and cookies) is 176.7°C, usually rounded to 175°C or 180°C since home ovens do not do decimals. A hot 200°C European oven is 392°F. Bread's classic 220°C is 428°F, and a slow 150°C is 302°F.
If your recipe gives a UK gas mark instead, gas mark 4 sits in the 350°F / 177°C neighbourhood, check a gas-mark chart for the exact rounded setting your oven dial expects.
Celsius is the everyday scale for most of the world, weather, cooking, thermostats. Fahrenheit remains the everyday scale in the United States. Kelvin is the scientific scale: it starts at absolute zero (the coldest physically possible temperature) and has no negative numbers, which is why physicists and chemists use it, K = °C + 273.15 with no rescaling.
The two everyday scales meet at exactly one point: −40°C = −40°F. Set °C × 9/5 + 32 equal to °C and solve: −40 × 1.8 + 32 = −40.
For a rough Fahrenheit reading, double the Celsius value and add 30: 20°C → 70°F (exact: 68°F). It is close enough for a weather check but not for cooking or medical temperatures. Reverse shortcut: subtract 30 from Fahrenheit and halve, 70°F → 20°C (exact: 21.1°C).
The biggest error is forgetting the order of operations: subtract 32 FIRST, then multiply by 5/9. Multiplying 68 × 5/9 gives 37.8, the wrong answer, because the 32-degree offset must come off first. In the other direction, multiply by 9/5 first, then add 32.
Another trap: using the rounded decimal 0.5556 instead of the exact fraction 5/9. Fine for everyday weather, but exact work, lab figures, engineering, should use the fraction.
Multiply by 9/5 (1.8) and add 32: °F = (°C × 9/5) + 32. For example, 25°C = (25 × 1.8) + 32 = 77°F.
Subtract 32 first, then multiply by 5/9: °C = (°F − 32) × 5/9. For example, (77 − 32) × 5/9 = 25°C.
32°F, which is 0°C. It is one of the two anchor points, the other is boiling at 212°F/100°C, that define the conversion formula.
98.6°F, normal human body temperature. 37 × 9/5 + 32 = 98.6 exactly. A fever is generally defined from 38°C (100.4°F).
−40 degrees. It is the only temperature where both scales agree: −40°C × 1.8 + 32 = −40°F.
Add 273.15: K = °C + 273.15. So 20°C = 293.15 K. Kelvin and Celsius degrees are the same size; only the zero point moves.
The coldest temperature physically possible: −273.15°C = −459.67°F = 0 K. Kelvin starts there, which is why it has no negative numbers.
Yes: double the Celsius value and add 30. 20°C → about 70°F (exact 68°F). Good for a weather check, not for ovens or thermometers.
176.7°C, usually rounded to 175°C or 180°C in recipes, since home ovens do not set fractions of a degree. 350°F is the classic moderate US oven setting.