How do I convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 and add 32. So 20 °C becomes 20 × 9/5 + 32 = 68 °F. To go the other way, subtract 32 first then multiply by 5/9.

How do I convert Celsius to Kelvin?

Add 273.15 to the Celsius value. 25 °C is 298.15 K. Kelvin uses the same degree size as Celsius, so the gap between two temperatures is identical in both scales — only the zero point differs.

What is the Rankine scale and how does it relate to Fahrenheit?

Rankine is an absolute scale that starts at absolute zero but uses Fahrenheit-sized degrees. Convert from Fahrenheit by adding 459.67, so 32 °F equals 491.67 °R. It is mostly used in some US engineering and thermodynamics work.

At what temperature are Celsius and Fahrenheit equal?

They read the same at −40, where −40 °C equals −40 °F. This is the single crossover point of the two scales and a handy sanity check for any converter.

What is absolute zero on each scale?

Absolute zero is 0 K, which equals −273.15 °C, −459.67 °F and 0 °R. Nothing can be colder, so the tool flags any value that would fall below it as physically impossible.

Is my data sent anywhere?

No. Every conversion is pure arithmetic performed in your browser using built-in JavaScript. No values are uploaded, logged or stored on a server.

Temperature Converter

A temperature converter that handles all four common scales — Celsius (°C), Fahrenheit (°F), Kelvin (K) and Rankine (°R) — using the exact defining formulas rather than rounded approximations. It is built for cooks, students, scientists and engineers who need a quick, trustworthy conversion without reaching for a phone app or a server round-trip. Type a value into the focused from/to box, or straight into any of the four scale cards, and every other field updates instantly.

How it works

The tool converts everything through Kelvin as a single canonical baseline, then fans the result back out to each scale. Working through one absolute scale keeps the maths consistent and avoids the rounding errors you get when chaining conversions one step at a time. Whichever field you last edited becomes the anchor: its raw text is preserved exactly while the other three are recomputed.

The conversions are governed by these relationships. Celsius and Kelvin share a degree size and differ only by the offset 273.15. Fahrenheit and Rankine share a degree size — each one is 5/9 of a Celsius degree. Fahrenheit and Rankine differ by the offset 459.67. Because the tool stores the canonical value as a single Kelvin number, the swap button can flip the from and to scales while preserving the exact physical temperature. The converter also knows that absolute zero is 0 K, so any entry that would compute below it is flagged as physically impossible — useful for catching a mistyped sign or a stray minus.

Worked example

Suppose you have a recipe written in Fahrenheit and your oven dial is in Celsius. Enter 350 and set the from scale to Fahrenheit. The tool computes the Kelvin baseline as (350 + 459.67) × 5/9 = 449.817 K, then reports 176.667 °C — round that to about 177 °C (a moderate oven). Switch the to scale to Kelvin and you read 449.82 K; to Rankine and you read 809.67 °R. A quicker everyday check: −40 °C and −40 °F are the same temperature, the one point where the two everyday scales meet.

Conversion reference

From → To	Formula
Celsius → Fahrenheit	F = C × 9/5 + 32
Fahrenheit → Celsius	C = (F − 32) × 5/9
Celsius → Kelvin	K = C + 273.15
Kelvin → Celsius	C = K − 273.15
Celsius → Rankine	R = (C + 273.15) × 9/5
Fahrenheit → Rankine	R = F + 459.67
Kelvin → Rankine	R = K × 9/5
Rankine → Kelvin	K = R × 5/9

A few anchor points to sanity-check any conversion: water freezes at 0 °C / 32 °F / 273.15 K / 491.67 °R, water boils at 100 °C / 212 °F / 373.15 K / 671.67 °R, and absolute zero sits at 0 K / −273.15 °C / −459.67 °F / 0 °R.

Every figure is calculated in your browser — no numbers are uploaded or stored.