Temperature Scales Explained
Celsius (°C) is the metric standard used by nearly every country. Water freezes at 0°C and boils at 100°C at standard atmospheric pressure. It's the everyday scale for weather, cooking, and medicine worldwide.
Fahrenheit (°F) is primarily used in the United States. Water freezes at 32°F and boils at 212°F. A useful rule of thumb: normal body temperature is 98.6°F (37°C). The scale was defined by Daniel Gabriel Fahrenheit in the 1720s.
Kelvin (K) is the SI base unit for thermodynamic temperature. Zero Kelvin (absolute zero, −273.15°C) is the theoretical point at which all molecular motion ceases. Kelvin is used throughout physics, chemistry, and astrophysics because it has no negative values.
Conversion Formulas
°C
°F
(°C × 9/5) + 32
e.g. 100°C → 212°F
°F
°C
(°F − 32) × 5/9
e.g. 32°F → 0°C
°C
K
°C + 273.15
e.g. 0°C → 273.15K
K
°C
K − 273.15
e.g. 373.15K → 100°C
Frequently Asked Questions
Multiply the Celsius value by 9/5 (or 1.8) and add 32. For example: 100°C × 1.8 + 32 = 212°F. The formula is
(°C × 9/5) + 32.Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example: (98.6 − 32) × 5/9 = 37°C. The formula is
(°F − 32) × 5/9.Absolute zero is 0 K, equivalent to −273.15°C (−459.67°F). It is the theoretical lowest possible temperature, at which all atomic thermal motion would cease. It has never been achieved in practice, though scientists have come within a fraction of a nanokelvin.
Celsius and Fahrenheit are equal at exactly −40°. This is sometimes called the "crossover point." You can verify it: (−40 × 9/5) + 32 = −40°F.
The converter listens for every keystroke on the input field and recalculates instantly. This means you see results as you type rather than having to click Calculate each time — ideal when quickly converting multiple values.
The thermometer SVG uses four colour zones: blue (below 0°C / freezing), teal (0–20°C / cool), green (20–37°C / comfortable), amber (37–60°C / warm), and red (above 60°C / hot or dangerous). The fill level and colour update live with every conversion.
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