Temperature converter

Convert temperature units from one value and its input unit, with every compatible unit shown together.

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Result

Degrees Celsius (°C): 0 °C
Degrees Fahrenheit (°F): 32 °F
Kelvin (K): 273.15 K

Not engineering advice. Have a licensed professional check every result. Not a substitute for a licensed engineer, the manufacturer's data or the authority having jurisdiction; confirm the code edition your jurisdiction has adopted. Converts units only; this is not a code reading. Exact unit definitions with no code limit, so no trade check is pending. Terms of use and estimate disclaimer.

Working

Convert to °C
$T_K = T_C + 273.15,\quad T_C = (T_F - 32)\frac{5}{9}$
0 °C using the defining Celsius, Fahrenheit and kelvin offsets and ratio
= 0 °C
Convert to °F
$T_K = T_C + 273.15,\quad T_C = (T_F - 32)\frac{5}{9}$
0 °C using the defining Celsius, Fahrenheit and kelvin offsets and ratio
= 32 °F
Convert to K
$T_K = T_C + 273.15,\quad T_C = (T_F - 32)\frac{5}{9}$
0 °C using the defining Celsius, Fahrenheit and kelvin offsets and ratio
= 273.15 K

Working is shown in the units each formula is written in; the result figures above follow the unit switch. A numeric input is taken to 15 significant digits before it is used (1033.2293579541322 kg is used as 1033.22935795413 kg); every echo of it shows that value, and a computed figure substituted into the working is quoted to 15 significant digits as well.

Notes

Converts units only; this is not a code reading. Results retain 13 significant digits; the last digit can reflect floating-point arithmetic.

Method

Exact unit arithmetic

K = C + 273.15; C = (F - 32) × 5/9. Absolute zero is 0 K, -273.15 °C or -459.67 °F.

How to read the result

Choose the unit of the entered value. Multiply by its exact SI factor, then divide by each output unit factor. Temperature uses its defining affine equations instead. Unit-bearing results retain 13 significant digits; no rounded table entry is used in the computation.

These are absolute temperatures, not temperature differences. Values below absolute zero are refused in the entered scale.

Limits and sources

Converts units only; this is not a code reading. No code-derived number or engineering limit is used. Not engineering advice. Have a licensed professional check every result.

Factors come from exact unit definitions. Source URLs were tried by plain GET on 2026-10-13 and returned HTTP 403, so comparison with the NIST printed rows remains unverified. The exact definitions and derivation are recorded in this tool's spec.

Formulas

Celsius and kelvin

K = C + 273.15

T_K = T_C + 273.15

Fahrenheit and Celsius

C = (F - 32) × 5/9; F = C × 9/5 + 32

T_C = (T_F - 32) 5/9

Basis: engineering method

Standard	Edition	Clause	What it covers
NIST SP 811, Guide for the Use of the International System of Units	n/a	Appendix B.8 and B.9	Exact unit definitions, SI prefixes and derived arithmetic. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8 ; https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9 . Source fetch 2026-10-13: HTTP 403; printed rows unverified.
NIST Handbook 44, unit definitions	n/a	Appendix C	International foot and inch; avoirdupois pound and ounce; US liquid gallon is 231 cubic inches. https://nvlpubs.nist.gov/nistpubs/hb/2026/NIST.HB.44-2026.pdf . Source fetch 2026-10-13: HTTP 403; printed rows unverified.

Rules are restated in our own words and computed for your inputs; no table or text from a standard is reproduced. The adopted edition varies by jurisdiction, so confirm the one your authority having jurisdiction enforces.

Inputs

Input	Unit	Range	Default
Value in the selected unit `value`		-1000000000000 to 1000000000000	0
Input unit `unit`	choice	C, F, K	C

Worked examples

Each example below is a test the calculator must pass before it ships. The expected values were worked out by a separate implementation.

Example	Expected result (each in its declared unit)
Zero degrees Celsius	F: 32 °F, K: 273.15 K
The minus forty crossing	F: -40 °F
Absolute zero	C: -273.15 °C, F: -459.67 °F

For AI agents

This calculator is also the MCP tool convert_temperature at https://elevatorcalc.com/api/mcp, using the same function as this page. See how to connect, the llms.txt file, or the JSON catalogue.