Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine — the four major temperature scales
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Support fast conversion of various units including length, area, volume, weight, temperature, etc.
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What is Temperature Conversion?
Temperature conversion translates a temperature reading from one scale to another. Unlike length or mass, temperature conversion is not a simple multiplication — each scale has a different zero point and, in the case of Fahrenheit, different-sized degrees. This makes a converter especially useful.
Four scales matter. Celsius (°C) sets water’s freezing point at 0 and boiling point at 100 — used by most of the world and in science. Fahrenheit (°F) sets freezing at 32 and boiling at 212 — used in the United States. Kelvin (K) is the scientific absolute scale, starting at absolute zero (−273.15°C). Rankine (°R) is Fahrenheit’s absolute counterpart, used in some US engineering.
Because the scales have different origins, you cannot convert between them with a single ratio — you need a formula that shifts the zero point first.
How to Convert Temperature
Temperature uses formulas instead of conversion rates, because each scale has a different zero point:
°F = °C × 1.8 + 32
°C = (°F − 32) ÷ 1.8
K = °C + 273.15
Example — convert 25°C to Fahrenheit:
25°C = 25 × 1.8 + 32 = 45 + 32 = 77°F
Example — convert 98.6°F (body temp) to Celsius:
98.6°F = (98.6 − 32) ÷ 1.8 = 66.6 ÷ 1.8 = 37°C
Key tip: The converter above applies the correct formula for each pair automatically. The common mistake is forgetting the +32 (or −32) shift and only multiplying by 1.8 — that gives wildly wrong answers.
Common Temperature Conversions
| Reference point | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20 | 68 | 293.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Water boils | 100 | 212 | 373.15 |
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 1.8 and add 32. The formula is °F = °C × 1.8 + 32. For example, 20°C = 20 × 1.8 + 32 = 68°F. A quick mental shortcut: double the Celsius number and add 30 — it is not exact but close enough for everyday temperatures.
What is the Kelvin scale used for?
Kelvin is the SI unit of temperature and is used in science and engineering because it starts at absolute zero (0 K = −273.15°C), the point where all thermal motion stops. Unlike Celsius and Fahrenheit, Kelvin does not use the degree symbol. It is essential for physics, chemistry, and any calculation involving gas laws or thermodynamics.
Why is Rankine rarely used in daily life?
The Rankine scale (°R) is the absolute-temperature equivalent of Fahrenheit — 0°R is absolute zero, just like 0 K, but its degrees are the same size as Fahrenheit degrees. It is used almost exclusively in some engineering fields in the United States (particularly aerospace and thermodynamics). For everyday use, Celsius and Fahrenheit are far more common.
What is normal body temperature in Celsius and Fahrenheit?
Normal human body temperature is about 37°C, which equals 98.6°F. A fever is generally considered to be 38°C (100.4°F) or higher. Room temperature is typically 20–22°C (68–72°F), and water freezes at 0°C (32°F) and boils at 100°C (212°F) at sea level.
Can temperature be negative?
Yes, in Celsius and Fahrenheit, negative temperatures are common — water freezes at 0°C, so a winter day at −10°C is normal. In Kelvin, however, there are no negative temperatures because 0 K is absolute zero, the lowest possible temperature. Nothing can be colder than absolute zero, where all thermal motion stops.