18 Fahrenheit to Celsius
18 °F ≈ -7.78 °C
18 degrees Fahrenheit is approximately -7.78 degrees Celsius.
How to convert 18 °F to °C
Use the formula °C = (°F − 32) × 5/9:
°C = (18 − 32) × 5/9°C = -14 × 5/9°C = -7.777778
So 18 °F = -7.777778 °C, or about -7.78 °C rounded.
Rounded values and quick estimate
- Rounded to a whole number: -8 °C
- Rounded to one decimal place: -7.8 °C
Quick mental estimate: subtract 30 and halve it. For 18 °F that gives about -6 °C — off by 1.78 °C (22.9%). Use the exact formula when precision matters.
18 Fahrenheit in other units
-7.78 °C is below the freezing point of water (0 °C / 32 °F), so expect ice and frost. In weather terms it is a cold winter day.
- Celsius
- -7.78 °C
- Degrees Réaumur
- -6.22 °Ré
- Degrees Delisle
- 161.67 °De
- Degrees Newton
- -2.57 °N
- Degrees Rømer
- 3.42 °Rø
- Kelvin
- 265.37 K
- Rankine
- 477.67 °R
18 °F and nearby values
About fahrenheit and celsius
The Fahrenheit scale puts water’s freezing point at 32 °F and boiling point at 212 °F. It is the everyday temperature scale in the United States.
The Celsius scale sets the freezing point of water at 0 °C and its boiling point at 100 °C (at sea level). It is used for everyday temperatures in almost every country.
Related conversions
Frequently asked questions
What is 18 Fahrenheit in Celsius?
18 degrees Fahrenheit is about -7.78 degrees Celsius (18 °F ≈ -7.78 °C).
How do you convert 18 °F to °C?
Apply °C = (°F − 32) × 5/9: °C = (18 − 32) × 5/9, °C = -14 × 5/9, °C = -7.777778.
How many degrees Fahrenheit is -7.78 °C?
-7.78 °C is about 18 degrees Fahrenheit.