Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin.
Temperature Conversion Formulas
Celsius and Fahrenheit use different zero points and scales: water freezes at 0 °C but 32 °F, and boils at 100 °C but 212 °F. That 180-degree Fahrenheit span (212−32) over the 100-degree Celsius span gives the 9/5 multiplier.
Kelvin is the SI base unit used in science: absolute zero (0 K, −273.15 °C) is the coldest possible temperature where molecular motion stops. Kelvin has no degrees symbol and never goes negative.
Worked Example: Convert 37 °C (body temperature) to °F
Step 1 — multiply by 9/5: 37 × 1.8 = 66.6
Step 2 — add 32: 66.6 + 32 = 98.6
Result: 37 °C = 98.6 °F (normal body temperature)
A fever threshold works the same way: 38 °C = 100.4 °F, which is why US medical charts flag 100.4 °F as the fever line.
Frequently Asked Questions
Why does Fahrenheit use 32 for freezing?
Daniel Fahrenheit set 0 °F as the coldest stable temperature he could make with a salt-ice mixture, and 96 °F as approximate body temperature — so water froze at 32 on his scale. The scale survived because of its fine degree resolution.
At what temperature are Celsius and Fahrenheit equal?
−40°. Solve F = C×9/5+32 with F = C: C = −40. It is a handy sanity check when converting weather temperatures.
Is 1 degree Celsius bigger than 1 degree Fahrenheit?
Yes. One Celsius degree spans 9/5 Fahrenheit degrees, so a 10 °C rise equals an 18 °F rise.
What is absolute zero in Celsius and Fahrenheit?
−273.15 °C and −459.67 °F. Nothing can be colder; it is the floor of the Kelvin scale where thermal motion reaches its minimum (quantum zero-point energy).
Authoritative Sources & Further Reading
Last reviewed: September 2026. This calculator provides estimates for educational purposes and is not financial, medical, or legal advice.
This calculation model has been mathematically audited for compliance with industry standard benchmarks (including standard amortization logic and clinical BMR guidelines).
Need help?
Check our guides for more information on how to use this calculator effectively.
Read our guides