Conversions
Celsius, Fahrenheit, Kelvin: All Three Explained
Morecalcs Team 2026-08-01· 6 min
The formulas, the history, and why Kelvin is the physics unit.
The three scales
- Celsius: 0 = water freezes, 100 = water boils (at 1 atm)
- Fahrenheit: 32 = water freezes, 212 = water boils
- Kelvin: 0 = absolute zero, no negative values
Conversion formulas
- C → F: F = C × 9/5 + 32
- F → C: C = (F − 32) × 5/9
- C → K: K = C + 273.15
Mental math
Double C, subtract 10%, add 32. Close enough for weather.
Why physicists use Kelvin
Thermodynamic equations require an absolute scale. Zero Kelvin is where molecular motion stops.
Advertisement · in-content
More in Conversions
Unit Conversion Basics: Metric ↔ Imperial
The five conversions you'll use again and again.
Why the World Uses Metric (Except Three Countries)
A short history of the meter, the yard, and the SI system.
Bytes to Terabytes: What Each Size Actually Holds
KB vs KiB, and how much data your files really are.
mph, km/h, m/s: A Quick Speed Conversion Guide
Instant mental conversions for road, track, and physics.