Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine.
BSc Physics (Hons), MEng Mechanical Engineering
Physicist and engineer focused on translating complex scientific and mathematical calculations into accessible everyday tools.
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About the Temperature Converter
Temperature is measured using several different scales, the two most common being Celsius (used by most of the world) and Fahrenheit (used primarily in the United States). Understanding how to convert between them is one of the most frequently searched unit conversions on the internet — whether you're cooking, travelling, reading weather forecasts, or following a scientific paper.
The Celsius scale was defined so that 0°C is the freezing point of water and 100°C is the boiling point at standard atmospheric pressure (101.325 kPa). The Fahrenheit scale has 32°F as the freezing point and 212°F as the boiling point, making the conversion formula: °F = (°C × 9/5) + 32. The scale was originally anchored to brine (0°F) and human body temperature (approximately 96°F, later refined to 98.6°F). Kelvin, the SI base unit for thermodynamic temperature, sets absolute zero (−273.15°C, the coldest theoretically possible temperature) as its zero point.
Knowing common temperature landmarks in both scales is more useful than memorising the formula for everyday use. Room temperature: 20°C = 68°F. Body temperature: 37°C = 98.6°F. A hot summer day: 35°C = 95°F. Oven baking: 180°C = 356°F. Boiling water: 100°C = 212°F. The "mirror point" where both scales give the same number is −40° (both −40°C and −40°F).
How it works
Celsius to Fahrenheit: °F = (°C × 9/5) + 32 Fahrenheit to Celsius: °C = (°F − 32) × 5/9 Celsius to Kelvin: K = °C + 273.15 Kelvin to Celsius: °C = K − 273.15 Quick approximation (accurate to ±1°C): °F → °C: double the Fahrenheit, subtract 30, halve it °C → °F: double the Celsius, add 30
Where
9/5The ratio of degree-sizes: a Fahrenheit degree is 5/9 the size of a Celsius degree+32The offset — Fahrenheit's 0° is 32° below Celsius's 0° (water's freezing point)+273.15Absolute zero offset — 0 K is −273.15°C, the coldest possible temperatureWorked example
37°C (body temperature) to Fahrenheit:
°F = (37 × 9/5) + 32
= (37 × 1.8) + 32
= 66.6 + 32
= 98.6°F
350°F (oven temperature) to Celsius:
°C = (350 − 32) × 5/9
= 318 × 0.5556
= 176.7°C ≈ 177°C (Gas Mark 4)
Tips to improve your result
- 1.
The easiest mental conversion from Fahrenheit to Celsius: subtract 32, then halve the result (then add 10% for precision). E.g. 68°F → (68−32=36) → 36/2=18 → 18+1.8≈20°C.
- 2.
For cooking, memorise these oven equivalents: 160°C=Gas 3, 180°C=Gas 4, 200°C=Gas 6, 220°C=Gas 7. Most baking recipes work well at 180°C / 350°F.
- 3.
The only temperature where Celsius and Fahrenheit are equal is −40°. Below that, Fahrenheit numbers are larger in magnitude; above that, Celsius numbers become larger as temperature rises.
- 4.
Kelvin is used in physics, chemistry, and engineering when calculations depend on absolute temperature ratios. For example, the speed of sound is proportional to the square root of absolute temperature in Kelvin.
- 5.
Rankine is the Fahrenheit equivalent of Kelvin (absolute zero in Fahrenheit scale). It is used in some US engineering contexts. Rankine = Fahrenheit + 459.67.