Temperature Converter
Convert Celsius, Fahrenheit and Kelvin.
Converted value
32℉
What is temperature unit conversion?
Temperature conversion translates a value between Celsius (℃), Fahrenheit (℉) and Kelvin (K). Unlike length or weight, temperature units have different zero points (an affine relationship), so conversion requires a formula with an offset rather than simple multiplication.
How to use it
Enter a value, choose the from and to units, and the result updates automatically. Internally the value is first converted to Celsius, then from Celsius to the target unit.
°C→°F: F = C × 9/5 + 32
°C→K: K = C + 273.15
Formulas & reference points
Water freezes at 0℃ = 32℉ = 273.15K. Water boils (at 1 atm) at 100℃ = 212℉ = 373.15K.
Why does Fahrenheit use such odd numbers? Origins and a quick estimate
Around 1724, German physicist Daniel Fahrenheit set the freezing point of a saturated ammonium chloride brine at 0°F and the freezing point of pure water at 32°F, then divided the range between them into equal steps to build his scale. His early scale placed body temperature near 96°F; later, more precise re-calibration standardized the scale around water's freezing point at 32°F and boiling point at 212°F (1 atm), which is how normal body temperature ended up at about 98.6°F. Because of this origin, Fahrenheit doesn't line up neatly at 0 and 100 the way Celsius does.
When the exact formula (F = C × 9/5 + 32) is inconvenient to compute mentally, a common shortcut is F ≈ C × 2 + 30. Near 0°C (e.g. 10°C) the shortcut is nearly exact, but the error grows as temperature rises. As the table below shows, near body temperature (37°C) the shortcut is already off by 5.4°F, so it's best kept to casual small talk rather than anything precise.
| Celsius | Exact °F | Shortcut °F | Error |
|---|---|---|---|
| 0°C | 32.0°F | 30°F | 2.0°F |
| 10°C | 50.0°F | 50°F | 0.0°F |
| 20°C | 68.0°F | 70°F | 2.0°F |
| 37°C (body temp) | 98.6°F | 104°F | 5.4°F |
| 100°C (boiling) | 212.0°F | 230°F | 18.0°F |
All three scales share one reference point: absolute zero (-273.15°C = -459.67°F = 0K), the theoretical temperature at which particle motion is minimized. Only Kelvin sets this as its zero, which is why it never goes negative — and why science and engineering calculations always use Kelvin.