70°F=21.1111°C

To convert 70°F to Celsius, subtract 32 and then multiply by 5/9: (70 − 32) × 5/9 = 38 × 0.5556 = 21.1111°C. Subtracting 32 removes the offset between the two scales' zero points, and multiplying by 5/9 scales the result down from Fahrenheit degrees to the slightly larger Celsius degrees. The formula is the algebraic inverse of converting Celsius to Fahrenheit.

The Fahrenheit scale sets the freezing point of water at 32°F and the boiling point at 212°F, a 180-degree span. Celsius uses a more memorable 100-degree span between the same two water states, which is part of why it was adopted as the scientific and international standard. When you encounter Fahrenheit temperatures in American contexts — news weather reports, recipe instructions, clothing care labels, medical readings in older US documents — converting to Celsius helps you interpret them in terms that are more familiar if you grew up with the metric system.

21.1111°C is a meaningful temperature reference. Common Celsius benchmarks include 0°C (freezing), 20°C (comfortable room temperature), 37°C (normal human body temperature), and 100°C (boiling water). Travelers moving between countries often need this conversion most urgently when reading a local weather app that uses a different scale, setting a foreign thermostat, or following cooking directions from a different region. A quick mental approximation: subtract 30 from the Fahrenheit value and halve the result (for example, 80°F → (80−30)/2 = 25°C) gives a rough but practical estimate.