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How It Works

This calculator converts between the four standard temperature scales — Celsius, Fahrenheit, Kelvin, and Rankine — using exact conversion formulas. Enter a value in one scale and instantly see it in all four.

Celsius and Kelvin share the same degree size (1 °C = 1 K change), while Fahrenheit and Rankine share a smaller degree (1 °F = 1 °R change). The key offsets are 273.15 (Celsius to Kelvin) and 459.67 (Fahrenheit to Rankine).

Example Problem

Convert a comfortable room temperature of 72 °F to all other scales.

  1. Celsius: TC = (5/9)(72 − 32) = 22.22 °C
  2. Kelvin: TK = 22.22 + 273.15 = 295.37 K
  3. Rankine: TR = 72 + 459.67 = 531.67 °R

Frequently Asked Questions

How do you convert Celsius to Fahrenheit?

Multiply the Celsius temperature by 9/5 and add 32. For example, 100 °C becomes (100 × 9/5) + 32 = 212 °F, which is the boiling point of water at standard pressure.

What is absolute zero in Fahrenheit and Celsius?

Absolute zero — the lowest possible temperature — is 0 K, −273.15 °C, or −459.67 °F. At this point, molecular motion essentially stops.

When should I use Kelvin instead of Celsius?

Use Kelvin for scientific calculations, especially gas laws, thermodynamics, and radiation formulas. Kelvin is required whenever a formula involves ratios or products of temperatures because it starts at absolute zero.

What is the Rankine scale used for?

Rankine is used in US engineering thermodynamics where Fahrenheit is standard but an absolute scale is needed. It works like Kelvin but with Fahrenheit-sized degrees. You will find it in HVAC, aerospace, and some combustion calculations.

At what temperature are Celsius and Fahrenheit equal?

Celsius and Fahrenheit read the same value at −40 degrees. Below that point Fahrenheit gives numerically lower values, and above it Fahrenheit gives numerically higher values.

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