How to convert fahrenheit to celsius
°C = ((x − 32) × 0.555555555555556) ÷ 1
Subtract 32 before multiplying by 5/9. A temperature change of 18°F is 10°C, but a temperature of 18°F is below 0°C.
Worked example
°C = ((68 − 32) × 0.555555555555556) ÷ 1
68 °F = 20 °C.
Conversion table in both directions
Values are generated by the same engine as the interactive converter.
| Input | °F → °C | °C → °F |
|---|---|---|
| -40 | -40 | -40 |
| 0 | -17.777778 | 32 |
| 10 | -12.222222 | 50 |
| 20 | -6.666667 | 68 |
| 25 | -3.888889 | 77 |
| 37 | 2.777778 | 98.6 |
| 100 | 37.777778 | 212 |
Unit definitions and sources
Absolute temperatures use offsets. Temperature intervals do not: a change of 1 °C is a change of 1 K or 1.8 °F. Values below absolute zero are rejected.
| Unit and system | Use | Definition | Relationship |
|---|---|---|---|
| Celsius (°C); si | Common units | Celsius measures temperature. c = (value in °C) × 1. Common use: Absolute temperature readings. | Exact definition; numerical display may be rounded |
| Fahrenheit (°F); us | Common units | Fahrenheit measures temperature. c = (value in °F − 32) × 0.5555555555555556. Common use: Absolute temperature readings. | Exact definition; numerical display may be rounded |
Sources: BIPM: International System of Units; NIST: SP 811 Appendix B.8: conversion factors
Precision of temperature conversions
These 2 temperature units convert through Celsius (°C). 2 have an exact defined relationship to the base unit and 0 are conventional or measured values. Results and the tables on this page come from the same engine, so a table value can be checked against the converter directly.
Standard display shows up to six decimal places, switching to scientific notation for very large or small values. Calculation uses JavaScript binary floating point independently of display rounding, so extra digits are not a claim about measurement accuracy. Each unit lists its own source; a citation records where the definition comes from, not an independent review. See Conversion methodology for the review and correction process.