Negative Temperature Converter
Convert below-zero temperatures between Celsius and Fahrenheit without sign mistakes, and see where the two scales cross at −40.
How to use the Negative Temperature Converter
- Enter the negative temperature (include the minus sign).
- Choose °C or °F.
- Read the converted value and the nearby table.
How it works
The formulas are the same as for positive temperatures — the trick is keeping the minus sign throughout. °F = (°C × 9/5) + 32: −10 °C × 1.8 = −18, and −18 + 32 = 14 °F. Going the other way, °C = (°F − 32) × 5/9: (−4 − 32) = −36, and −36 × 5/9 = −20 °C.
Above −40 the Fahrenheit number is higher; below −40 the Celsius number is higher (less negative). At exactly −40 they are equal.
Negative temperature chart
| °C | °F | °C | °F |
|---|---|---|---|
| -1 | 30 | -25 | -13 |
| -5 | 23 | -30 | -22 |
| -10 | 14 | -35 | -31 |
| -15 | 5 | -40 | -40 |
| -18 | 0 | -45 | -49 |
| -20 | -4 | -50 | -58 |
| -21 | -6 | -60 | -76 |
| -23 | -9 | -73 | -99 |
Frequently asked questions
What is −40 °C in Fahrenheit?
−40 °F — the two scales meet at −40.
What is −18 °C in Fahrenheit?
About 0 °F (−0.4 °F), the standard home freezer setting.
What is 0 °F in Celsius?
−17.8 °C.
What is −30 °C in Fahrenheit?
−22 °F.