How to use this calculator
Type a temperature into either the Celsius or Fahrenheit field and the other will update instantly. You can enter negative numbers, decimals, or any value you need. The conversion works in both directions, so there is no need to select which way you want to convert.
Below the converter you will find reference tables for common temperature scenarios including weather ranges, cooking and oven temperatures, body temperature and fever thresholds, and scientific reference points. These tables are useful when you need a quick lookup without entering a specific number.
The page also includes a mental math shortcut for quick estimates: double the Celsius value and add 30. This approximation works well for everyday weather temperatures and is handy when you are traveling and do not have a calculator available.
Understanding the Celsius and Fahrenheit scales
The Fahrenheit scale sets water's freezing point at 32 degrees and boiling point at 212 degrees, creating a 180 degree span between the two. The Celsius scale uses 0 for freezing and 100 for boiling, making it more intuitive for scientific work. The conversion formula, multiply by 9/5 and add 32, bridges the gap between these two reference systems.
In daily life, Fahrenheit offers finer granularity for weather since outdoor temperatures usually fall between 0 and 100 on the Fahrenheit scale. Celsius is used by the vast majority of the world and is standard in science, medicine, and international commerce. Knowing both scales is valuable for cooking with international recipes, understanding weather forecasts while traveling, and interpreting medical temperature readings.
Frequently Asked Questions
What is room temperature in both scales?
Room temperature is generally considered 20 to 22°C, which equals 68 to 72°F. Most thermostat guides recommend this range for both comfort and energy efficiency. Office buildings are typically kept at about 21°C (70°F).
What is the formula for converting between Celsius and Fahrenheit?
To convert Celsius to Fahrenheit: multiply by 9/5 (or 1.8) and add 32. The formula is °F = (°C × 9/5) + 32. To go the other direction, subtract 32 from Fahrenheit and multiply by 5/9. The formula is °C = (°F − 32) × 5/9.
Why do the US and most other countries use different scales?
Fahrenheit was created by Daniel Gabriel Fahrenheit in 1724 and became standard in English speaking countries. Celsius, created by Anders Celsius in 1742, became part of the metric system that most countries adopted in the 19th and 20th centuries. The United States retained Fahrenheit for daily use while adopting Celsius in scientific and medical settings.
At what temperature are Celsius and Fahrenheit equal?
The two scales meet at exactly negative 40 degrees. At negative 40°C, the formula gives (negative 40 × 9/5) + 32 = negative 72 + 32 = negative 40°F. This is the only point where both scales show the same number, and it represents extremely cold conditions found in arctic regions and severe winter weather.