Negative Fahrenheit to Celsius — Sub-Zero Temperature Guide
- -40°F equals -40°C — the one temperature where both scales agree. 0°F is -17.8°C. 32°F is 0°C. Here is the full guide to negative temperature conversions.
Table of Contents
-40°F = -40°C. That is the one temperature where Fahrenheit and Celsius are identical — a fact worth memorizing for cold-weather reference. Below that crossing point, Celsius numbers are always lower (colder) than their Fahrenheit equivalents.
To convert any negative Fahrenheit temperature to Celsius: subtract 32, then multiply by 5/9. The same formula as positive temperatures — it handles negative numbers exactly the same way.
Negative Temperature Conversion Table
| Fahrenheit | Celsius | Context |
|---|---|---|
| 32°F | 0°C | water freezes |
| 20°F | -6.7°C | cold winter day |
| 14°F | -10°C | cold continental winter |
| 0°F | -17.8°C | very cold (common US winter low) |
| -4°F | -20°C | extreme cold |
| -13°F | -25°C | dangerous windchill territory |
| -22°F | -30°C | arctic conditions |
| -40°F | -40°C | Fahrenheit = Celsius crossover point |
| -58°F | -50°C | coldest inhabited places on Earth |
| -108°F | -78°C | dry ice sublimation point |
| -320°F | -196°C | liquid nitrogen boiling point |
Why -40 Is the Crossover Point
The two temperature scales cross at -40 because of their different offset and slope. Fahrenheit uses 32 as the freezing point with 180 degrees to boiling. Celsius uses 0 as freezing with 100 degrees to boiling. Setting the formulas equal to each other: if C = F, then F = (F - 32) × 5/9. Solving: 9F = 5F - 160, so 4F = -160, so F = -40.
At temperatures below -40, Celsius readings are always lower numbers than Fahrenheit (e.g., -50°C = -58°F). Above -40, Celsius numbers are higher than Fahrenheit (e.g., 0°C = 32°F).
Sell Custom Apparel — We Handle Printing & Free ShippingCold Storage and Industrial Temperature Conversions
Common cold storage and industrial negative temperatures:
- Freezer storage: 0°F (-17.8°C) — standard home freezer
- Deep freeze storage: -10°F (-23.3°C) — commercial long-term storage
- Flash freezing: -40°F (-40°C)
- CO2 dry ice: -109.3°F (-78.5°C)
- Liquid nitrogen: -320.4°F (-196°C)
- Liquid oxygen: -297.3°F (-183°C)
Absolute Zero and Kelvin
The coldest possible temperature is absolute zero: -273.15°C = -459.67°F = 0 Kelvin. Nothing can be colder than absolute zero because it represents the complete absence of thermal energy.
The unit converter supports Kelvin in the Temperature category alongside Celsius and Fahrenheit. Kelvin is used in science, cryogenics, and physics calculations.
Convert Any Temperature Instantly
Celsius, Fahrenheit, Kelvin — positive or negative, the converter handles all of it free.
Open Unit Converter FreeFrequently Asked Questions
What is -40 Fahrenheit in Celsius?
-40°F equals exactly -40°C. This is the one point where Fahrenheit and Celsius are the same value.
What is 0 Fahrenheit in Celsius?
0°F = -17.78°C. Using the formula: (0 - 32) × 5/9 = -17.78°C.
How do you convert negative Fahrenheit to Celsius?
Same formula as positive: C = (F - 32) × 5/9. For -20°F: (-20 - 32) × 5/9 = -52 × 5/9 = -28.89°C.
Which is colder -40°C or -40°F?
Neither — they are exactly equal. -40°F = -40°C. This is the only temperature where both scales read the same.
