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🌡️ Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, and Rankine — live and bidirectional. Handles the offset math correctly (temperature scales don't share the same zero, so a plain multiplier won't do).

Try:
Freezing (0 °C) Boiling (100 °C) Body (37 °C) Room (72 °F) Absolute zero (0 K) −40 (C = F)
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About the Temperature Converter

The Temperature Converter turns any temperature into every other common scale at once — Celsius, Fahrenheit, Kelvin, and Rankine. Because temperature scales don't share the same zero, converting between them is not a simple multiplier — the tool applies the correct offset math so results are exact.

Everything runs in your browser. Nothing you type leaves your device.

Common uses

  • Weather & travel — US uses °F, most of the world uses °C.
  • Cooking & ovens — 350 °F = 177 °C is a common bake temperature.
  • Body temperature & fever — 100.4 °F = 38 °C is a low-grade fever threshold.
  • Science & physics — Kelvin is the SI base unit for temperature.
  • US engineering — Rankine still appears in some thermodynamics textbooks and HVAC calculations.

The four scales explained

Celsius (°C) — anchors at water freezing (0 °C) and boiling (100 °C) at sea level. Standard everywhere except the US, Belize, and a few islands.

Fahrenheit (°F) — anchors at brine freezing (0 °F, roughly the coldest a saltwater mix could get in Fahrenheit's 1720s lab) and human body temperature (originally 96 °F, later refined). Water freezes at 32 °F and boils at 212 °F.

Kelvin (K) — same step size as Celsius, but starts at absolute zero (−273.15 °C). No negative temperatures. The SI base unit; used in all physics.

Rankine (°R) — Kelvin's Fahrenheit cousin. Same step size as Fahrenheit but zeroed at absolute zero (−459.67 °F). Rare outside US thermodynamics classes.

Exact conversion formulas

  • °F = °C × 9/5 + 32
  • °C = (°F − 32) × 5/9
  • K = °C + 273.15
  • °R = °F + 459.67
  • K = °R × 5/9

Under the hood the tool converts everything to Celsius first, then out to each other scale — same math as above, just centralized so results stay perfectly consistent across all four fields.

Reference points

  • Absolute zero — 0 K = −273.15 °C = −459.67 °F = 0 °R
  • Water freezes — 0 °C = 32 °F = 273.15 K
  • Room temperature — 20 °C = 68 °F = 293.15 K
  • Body temperature — 37 °C = 98.6 °F = 310.15 K
  • Water boils (1 atm) — 100 °C = 212 °F = 373.15 K
  • −40 — the one point where °C and °F are equal (−40 °C = −40 °F)

Below absolute zero — a note

Absolute zero (0 K) is the theoretical lowest possible temperature. If you type a value that would fall below it (say, −300 °C), the Kelvin and Rankine fields will still compute a negative number — but that's physically impossible. The tool highlights sub-zero-Kelvin values so it's obvious.

Privacy

All conversion runs client-side. Nothing leaves your browser.

Frequently asked questions

Multiply Celsius by 9/5 and add 32. So 20 °C × 9/5 + 32 = 68 °F. The reverse: (°F − 32) × 5/9.
Subtract 32, then multiply by 5/9. Example: (98.6 °F − 32) × 5/9 = 37 °C. The quick mental shortcut: subtract 30 and halve — close for casual weather use, exact for math.
Absolute zero is the theoretical lowest possible temperature — the point at which all thermal motion stops. It equals 0 K = −273.15 °C = −459.67 °F. Nothing in the universe can be colder.
Kelvin is the SI base unit of temperature — used across physics, chemistry, and engineering because it starts at absolute zero, so temperatures are always non-negative and thermodynamic formulas work cleanly.
Rankine (°R) is an absolute-zero-anchored version of Fahrenheit — same step size as °F, but zeroed at absolute zero (−459.67 °F). It's rare outside US thermodynamics and HVAC engineering.