21 degrees Celsius = 69.80°F (294.15 K). Use the copy buttons below for any format, or enter a custom value in the converter.
The Celsius scale sets 0°C at the freezing point of water and 100°C at its boiling point. The Fahrenheit scale, used primarily in the United States, sets those same points at 32°F and 212°F. To convert Celsius to Fahrenheit, multiply by 9/5 and add 32: °F = (°C × 9/5) + 32. For 21°C: (21 × 1.8) + 32 = 69.80°F.
21°C
69.80°F
294.15 K
Fahrenheit
69.80°F
Kelvin
294.15 K
Full (°C to °F)
21°C = 69.80°F
Full (°C to K)
21°C = 294.15 K
Standard indoor comfort
21°C is widely considered the ideal indoor temperature for productivity and comfort. It's the benchmark used in many building codes and workplace health guidelines.
Enter any Celsius value to convert it live to Fahrenheit and Kelvin.
Here are three everyday situations where knowing that 21°C = 69.80°F makes a practical difference.
If a recipe involves simmering, fermenting, or proofing at 21°C, that's 69.80°F. For example, bread dough proofing at 25–30°C, chocolate tempering at 31–32°C, and sous-vide cooking at 55–65°C all require precise Celsius-to-Fahrenheit conversions when using US kitchen tools.
You're checking the weather for a trip abroad and the forecast shows 21°C. That's 69.80°F. Light clothing is fine — it's a pleasant day. Most weather apps let you switch between °C and °F, but knowing the conversion helps when reading local signage or talking to locals.
In a chemistry or physics class, temperatures are often given in Celsius and need to be converted for US-format worksheets, or converted to Kelvin for thermodynamics problems. 21°C = 69.80°F = 294.15 K. The Kelvin scale is used in the ideal gas law (PV = nRT) and other thermodynamic equations where absolute zero (0 K = −273.15°C) is the reference point.
See how 21°C compares to nearby temperatures in both Celsius and Fahrenheit.
Common questions about 21°C and its Fahrenheit equivalent, answered.