Fahrenheit to Celsius Converter

Convert Fahrenheit to Celsius

Fahrenheit to Celsius converts American temperature readings to the metric scale used worldwide. The formula subtracts 32 from the Fahrenheit value, then multiplies by 5/9. This covers weather forecasts, oven settings, medical readings, and scientific data that cross between US and international systems.

Conversion Formula

C = (F - 32) × 5/9

Worked example: converting 77°F (a warm day):

1. Subtract 32: 77 - 32 = 45
2. Multiply by 5/9: 45 × 5/9 = 25
3. Result: 77°F = 25°C

For a quick mental estimate, subtract 30 and divide by 2. This gives you a number within about 2 degrees of the actual value for everyday temperatures.

Extended Conversion Table

Real-World Use Cases

Weather Forecasts

When you read a US weather report showing 85°F, that is 29.4°C. International weather apps and most world news outlets report in Celsius. Converting helps you compare forecasts when traveling or reading global weather data.

Cooking and Baking

US recipes typically list oven temperatures in Fahrenheit. A recipe calling for 350°F means 177°C. European cookbooks use Celsius, so you need the reverse conversion when adapting recipes across regions. Gas mark settings on UK ovens also map to Celsius ranges.

Medical Readings

A body temperature of 100.4°F signals a fever at 38°C. Most medical equipment worldwide reports in Celsius. If you are tracking a child’s temperature from a US-bought thermometer and reporting to a doctor in another country, converting ensures accurate communication.

HVAC and Indoor Climate

Thermostat settings differ by region. US homes typically target 70°F (21°C) for comfort. European HVAC systems are calibrated in Celsius. When comparing energy efficiency ratings or purchasing heating equipment internationally, understanding both scales matters.

Scientific Experiments

Lab protocols often specify temperatures in Celsius or Kelvin. If your reference material uses Fahrenheit, you need accurate conversion. A 5-degree error in a chemistry experiment can change reaction outcomes entirely.

Gotchas and Common Mistakes

Rounding Errors Add Up

The conversion factor 5/9 is a repeating decimal (0.5555…). Rounding to 0.56 before multiplying introduces a 0.8% error at every step. Always do the full multiplication, then round your result to the precision you need.

Confusing the Formula Direction

The most common mistake is multiplying by 9/5 instead of 5/9. If you multiply by 9/5, you are going the wrong direction (Celsius to Fahrenheit). Remember: going from the “bigger” unit (Fahrenheit) to the “smaller” unit (Celsius) means multiplying by a fraction less than 1.

Negative Temperatures Are Tricky

At -40°, both scales read the same number. Below that, Fahrenheit numbers are actually smaller than their Celsius equivalents. The mental shortcut (subtract 30, divide by 2) breaks down below about 20°F.

Oven Thermostat Variance

Your oven’s actual temperature can differ from the dial setting by 25°F or more. Converting the dial number to Celsius does not fix this. Use an oven thermometer for precision baking.

FAQs

What is the formula to convert Fahrenheit to Celsius?

The formula is C = (F - 32) × 5/9. Subtract 32 to shift the scale, then multiply by 5/9 to adjust for the different unit sizes. For example, 77°F becomes (77 - 32) × 5/9 = 25°C.

What is 72 Fahrenheit in Celsius?

72°F equals 22.2°C. This is a standard comfortable room temperature and the typical setting for central air conditioning in US homes.

What is 98.6 Fahrenheit in Celsius?

98.6°F equals exactly 37°C. This is the average human body temperature. A reading above 38°C (100.4°F) is generally considered a fever.

How do I estimate Fahrenheit to Celsius in my head?

Subtract 30 from the Fahrenheit value, then divide by 2. For 86°F: 86 - 30 = 56, divided by 2 = 28°C (actual: 30°C). The estimate works best between 50°F and 100°F for everyday weather comparisons.

What is 0 Fahrenheit in Celsius?

0°F equals -17.8°C. This is a common winter temperature in the northern United States and a standard reference point for cold weather gear ratings.

Why does the US use Fahrenheit while most countries use Celsius?

Fahrenheit was the first standardized temperature scale, created in 1724. The US adopted it for everyday use and never switched during metrication. Most other countries moved to Celsius in the 20th century for its simplicity: 0° is freezing, 100° is boiling.

For the reverse conversion, see Celsius to Fahrenheit. For other unit conversions, try the full Unit Converter.