Temperature conversion requires both scaling and an offset. Multiplying alone is not enough when converting Celsius and Fahrenheit.
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Conversion formulas
- Fahrenheit = Celsius × 9 ÷ 5 + 32
- Celsius = (Fahrenheit − 32) × 5 ÷ 9
- Kelvin = Celsius + 273.15
- Celsius = Kelvin − 273.15
Quick reference points
| Celsius | Fahrenheit | Kelvin |
|---|---|---|
| −40 | −40 | 233.15 |
| 0 | 32 | 273.15 |
| 20 | 68 | 293.15 |
| 37 | 98.6 | 310.15 |
| 100 | 212 | 373.15 |
Why −40 is special
Celsius and Fahrenheit use different scale sizes and zero points, but their lines intersect at −40. Therefore −40°C equals −40°F.
Absolute zero
Zero kelvin equals −273.15°C. A physical thermodynamic temperature below zero kelvin is rejected by the converter.
Rounding
Keep extra decimals during the calculation and round only the final result. Weather values often need no more than one decimal, while scientific work may require uncertainty analysis and calibrated measurements.