Temperature Converter
Convert temperatures between Celsius, Fahrenheit, and Kelvin in real time. Unlike most unit conversions, temperature scales are offset from each other — not just scaled — so the tool applies the correct formula for every combination automatically.
How It Works
Temperature conversion is fundamentally different from length or weight conversion because the three common scales — Celsius, Fahrenheit, and Kelvin — do not share the same zero point. You cannot simply multiply by a fixed factor.
Celsius (°C) was defined so that 0° is the freezing point of water and 100° is the boiling point at standard atmospheric pressure. It is the standard temperature scale throughout most of the world and is used in all scientific contexts except thermodynamics.
Fahrenheit (°F) was established by Daniel Gabriel Fahrenheit in 1724. He set 0°F as the lowest temperature he could achieve with a brine solution and 96°F as approximate human body temperature. Modern definitions fix the freezing point of water at 32°F and boiling at 212°F, giving a 180-degree span versus Celsius's 100-degree span. The ratio 180/100 = 9/5 appears in all Celsius-Fahrenheit formulas.
Kelvin (K) is the SI thermodynamic temperature scale. It uses the same degree size as Celsius but starts at absolute zero — the lowest possible temperature, where all molecular motion stops. Absolute zero is −273.15°C = −459.67°F = 0 K. Note that Kelvin values have no degree symbol by convention.
The formulas:
• °C to °F: F = C × 9/5 + 32
• °F to °C: C = (F − 32) × 5/9
• °C to K: K = C + 273.15
• K to °C: C = K − 273.15
• °F to K: convert to °C first, then add 273.15
• K to °F: subtract 273.15 to get °C, then apply °C→°F formula
Worked example — Body temperature:
Normal human body temperature is 37°C. In Fahrenheit: 37 × 9/5 + 32 = 66.6 + 32 = 98.6°F.
Worked example — Water boils:
100°C → F = 100 × 9/5 + 32 = 180 + 32 = 212°F → K = 100 + 273.15 = 373.15 K.
Worked example — Convert a cold winter day:
−10°C → F = −10 × 1.8 + 32 = −18 + 32 = 14°F. At this temperature, exposed skin can experience frostbite within 30 minutes.
Worked example — Oven temperature:
A recipe calls for 375°F. Convert to Celsius: C = (375 − 32) × 5/9 = 343 × 0.5556 = 190.6°C. Set your oven to 190°C (or 200°C for fan-assisted ovens, which are typically 10–20°C hotter).
This converter handles all six direction combinations internally by converting through Celsius as an intermediate step.
Frequently Asked Questions
What is 37 degrees Celsius in Fahrenheit?
37°C = 98.6°F — normal human body temperature. The formula: F = 37 × 9/5 + 32 = 66.6 + 32 = 98.6°F.
What is absolute zero?
Absolute zero is 0 K = −273.15°C = −459.67°F. It is the lowest theoretically possible temperature, where all classical molecular motion ceases. It has never been fully achieved, though laboratories have reached within nanokelvins of it.
Why does Fahrenheit have 32 as the freezing point of water?
Fahrenheit originally set 0°F as the lowest temperature achievable with a saltwater/ice/ammonium chloride mixture and 96°F as body temperature. When the scale was later anchored to water's phase transitions, freezing fell at 32°F and boiling at 212°F — a 180° span vs Celsius's 100°.
How do I quickly approximate Celsius from Fahrenheit in my head?
Subtract 32, then divide by 2 (instead of multiplying by 5/9). The error is about 11%, but it is fast: 70°F → (70−32)/2 = 19°C (exact: 21.1°C). For a better shorthand: double the Celsius and add 30 to get Fahrenheit, or subtract 30 and halve to get Celsius.
Is Kelvin ever used in everyday life?
Kelvin appears in photography and display technology as "colour temperature" — a 5,500 K light source mimics daylight, while 2,700 K is warm (incandescent) light. It is also used in weather science, thermodynamics, and astronomy.