Fahrenheit to Celsius Converter
Convert Fahrenheit to Celsius instantly with our free online calculator. Essential for understanding weather forecasts, cooking temperatures, scientific calculations, and travel to metric countries.
Conversion Formulas
| Conversion | Formula | Example |
|---|---|---|
| °F to °C | (°F - 32) × 5/9 | 68°F = 20°C |
| °C to °F | (°C × 9/5) + 32 | 20°C = 68°F |
Temperature Reference Chart
| Fahrenheit | Celsius | Condition |
|---|---|---|
| 32°F | 0°C | Water freezes |
| 50°F | 10°C | Cool weather |
| 68°F | 20°C | Room temperature |
| 77°F | 25°C | Warm weather |
| 98.6°F | 37°C | Body temperature |
| 100°F | 37.8°C | Hot weather |
| 212°F | 100°C | Water boils |
Cooking Temperature Guide
| Fahrenheit | Celsius | Cooking Use |
|---|---|---|
| 250°F | 121°C | Slow roasting |
| 325°F | 163°C | Baking cakes |
| 350°F | 177°C | Standard baking |
| 375°F | 191°C | Roasting |
| 400°F | 204°C | High-heat roasting |
| 425°F | 218°C | Pizza, bread |
| 450°F | 232°C | Very high heat |
| 500°F | 260°C | Broiling |
Quick Mental Conversion
For approximate conversions:
- °F to °C: Subtract 30, then divide by 2
- °C to °F: Multiply by 2, then add 30
Conversion Code Example
``javascript
function fahrenheitToCelsius(f) {
return (f - 32) * 5 / 9;
}
function celsiusToFahrenheit(c) {
return (c * 9 / 5) + 32;
}
// Examples
console.log(fahrenheitToCelsius(68)); // 20
console.log(celsiusToFahrenheit(20)); // 68
`
Weather Interpretation
| Temp Range | Fahrenheit | Celsius | Feel |
|---|---|---|---|
| Freezing | < 32°F | < 0°C | Ice, snow |
| Cold | 32-50°F | 0-10°C | Winter coat |
| Cool | 50-65°F | 10-18°C | Light jacket |
| Comfortable | 65-75°F | 18-24°C | T-shirt |
| Warm | 75-85°F | 24-30°C | Summer clothes |
| Hot | 85-100°F | 30-38°C | Stay cool |
| Extreme | > 100°F | > 38°C | Dangerous heat |
Use this converter for accurate temperature conversions between Fahrenheit and Celsius.Why This Is Not a Multiplication
Every other unit conversion is a ratio: doubling the input doubles the output. Temperature
is not, because the two scales put their zero in different places.
| Fahrenheit | Celsius | |
|---|---|---|
| Water freezes | 32°F | 0°C |
| Water boils | 212°F | 100°C |
| Zero means | the freezing point of a brine solution Fahrenheit could reproduce in 1724 | the freezing point of water |
| Degrees between freezing and boiling | 180 | 100 |
So the conversion has two parts: scale the degree size by
0.5556, then shift
the origin.A Temperature and a Temperature Difference Are Different Things
This is the error that reaches production code. Converting "it is 20°F" and
converting "it rose by 20°F" are not the same operation:
| Quantity | Conversion |
|---|---|
| An absolute temperature | Scale and shift |
| A difference or a rate | Scale only |
A rise of 1°C is a rise of 1.8°F, not 33.8°F. Weather APIs, thermostat deltas and materials
data all carry differences, and a converter applied blindly to them is wrong by the offset.Negative Values and Absolute Zero
Celsius and Fahrenheit both go below zero; Kelvin does not. Absolute zero is 0 K, −273.15 °C
and −459.67 °F, and no temperature below it exists — a converter returning a negative Kelvin
value has been given an impossible input.
−40 is the one temperature where Celsius and Fahrenheit agree. It falls out of solving
x = x × 9/5 + 32, and it is a useful sanity check: if your conversion does not produce
−40 °F for −40 °C, the formula is wrong.
In Code
`javascript
// Absolute temperatures
const cToF = (c) => c * 9 / 5 + 32;
const fToC = (f) => (f - 32) * 5 / 9;
const cToK = (c) => c + 273.15;
// Differences — scale only, never shift
const deltaCToF = (dc) => dc * 9 / 5;
`
Note that Kelvin takes no degree sign: it is written 293 K, never 293 °K`.