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Temperature Converter

Water's 100 °C boiling point converts to precisely 212 °F and 373.15 K under the exact formulas F = C × 9/5 + 32 and K = C + 273.15. Temperature is the one everyday conversion you cannot do with a single multiplication, because Celsius, Fahrenheit, and Kelvin place their zero points differently, so this converter applies those formulas rather than a single factor.

In Fahrenheit
212°F
100 °C = 212 °F = 373.15 K
At or above water's boiling point
Water boils at 100 °C (212 °F) at sea level; lower pressure at altitude lowers this.
Where it sits
-40°C to 100°C
100°C
-40°F-4°F32°F68°F104°F140°F176°F
-40°C-20°C0°C20°C40°C60°C80°C100°Cwater freezeswater boils
Value
From
To
A reading, not a change
This converts a temperature point. A 10 C rise equals an 18 F rise — not 50 F — because Celsius and Fahrenheit put their zero in different places, so a reading and a difference convert differently.
The physical floor
Kelvin counts up from absolute zero: 0 K = -273.15 C, the coldest anything can be. A Kelvin result below zero would be physically impossible.
Ask a follow-up
Uses your inputs above
212 in fahrenheit. Want to try a variation?

The math

Reviewed 2026
Formula
F = C·9/5 + 32; K = C + 273.15

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Example: how temperature is calculated

Step-by-step with default inputs

Suppose you put the default values into Temperature Converter:

Value
100
From
Celsius (°C)
To
Fahrenheit (°F)

Plug those into the formula F = C·9/5 + 32; K = C + 273.15 and the result is:

In Fahrenheit
212°F

How does the temperature converter work?

Temperature Converter uses the formula shown in the math card and cites NIST temperature scales. Inputs are validated for sensible ranges; results are computed client-side for instant feedback and do not leave your browser.

References: NIST temperature scales.

Last reviewed July 2, 2026 · Editorial policy

Frequently asked questions

What temperature is the same in Celsius and Fahrenheit?

Minus 40 degrees. Setting C equal to F in the formula F = C × 9/5 + 32 and solving gives −40, the single point where both scales read the same number.

How do I convert Celsius to Fahrenheit in my head?

Double the Celsius number and add 30 for a quick estimate; the exact rule is multiply by 1.8 and add 32. The estimate matches exactly at 10 °C (50 °F) and drifts by a few degrees at hotter or colder temperatures.

Can a temperature in Kelvin be negative?

No. Zero kelvin is absolute zero — the same temperature as −273.15 °C — so the Kelvin scale starts at zero and has no negative values.

How accurate is this temperature calculator?

The math is deterministic — the same inputs always produce the same output, and the formula is shown above. Accuracy of the answer for your situation depends on how well your inputs match reality and how well the formula models the question.

Why does Google show a slightly different conversion?

For most units the answer is identical to many decimal places. Differences usually come from currency rates (which fluctuate intraday — this tool shows the ECB's daily reference rates) or rounding. We display up to 4 decimals.

How do I share my result?

Hit Share at the top of the page. Every input you change is encoded in the URL, so a permalink reproduces exactly what you see. No account needed.