The formula this converter uses
Converting temperatures requires adjusting both the zero-point offset and the degree scale size between Fahrenheit and Celsius systems.
Fahrenheit to Celsius Formula
°C = (°F − 32) × 5/9 or °C = (°F − 32) ÷ 1.8
Example: Converting 98.6°F to °C
(98.6 − 32) × 5/9 = 66.6 × 5/9 = 37°C
Quick Fahrenheit to Celsius reference table
Common reference temperatures for weather, cooking, and health metrics:
| Fahrenheit (°F) | Celsius (°C) | Significance |
|---|---|---|
| −40°F | −40°C | Equal temperature intersection |
| 0°F | −17.78°C | Freezing point of brine solution |
| 32°F | 0°C | Freezing point of pure water |
| 68°F | 20°C | Standard room temperature |
| 98.6°F | 37°C | Average human body temperature |
| 212°F | 100°C | Boiling point of water at sea level |
How the Fahrenheit and Celsius scales differ
The Celsius scale (part of the International System of Units) anchors 0°C to the freezing point of water and 100°C to its boiling point, creating a clean 100-degree interval. The Fahrenheit scale places water's freezing point at 32°F and boiling point at 212°F, producing a 180-degree span. Because 180 ÷ 100 equals 1.8 (or 9/5), each degree Celsius is 1.8 times larger than a degree Fahrenheit, requiring both multiplication/division by 1.8 and a 32-degree offset subtraction during conversion.
Quick mental math trick for estimating °C
If you need a fast approximation without a calculator, use this two-step estimation rule:
- Subtract 30 from the Fahrenheit degree.
- Divide the result by 2.
For example, to estimate 72°F in Celsius: 72 − 30 = 42, and 42 ÷ 2 = 21°C (the exact value is 22.22°C). This simple shortcut is accurate within 1 to 2 degrees for most ambient weather temperatures.
How to use this converter
- Type the temperature value into the Fahrenheit (°F) input box.
- The equivalent temperature in Celsius (°C) updates instantly below.
- Use the formula box or reference chart to double-check key values.
Frequently asked questions
How do you convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature and then multiply by 5/9 (or divide by 1.8). For example, 68°F converted is (68 − 32) × 5/9 = 20°C.
What is the fast mental shortcut for Fahrenheit to Celsius?
Subtract 30 from the Fahrenheit number and divide by 2. For 70°F: 70 − 30 = 40, and 40 ÷ 2 = 20°C (exact answer is 21.11°C).
At what temperature are Fahrenheit and Celsius equal?
Fahrenheit and Celsius scales intersect at −40 degrees, where −40°F is equal to −40°C.
What is normal body temperature in Celsius?
Normal average human body temperature is 98.6°F, which converts to exactly 37°C.