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Temperature Converter
Convert temperatures between Celsius, Fahrenheit and Kelvin with affine formulas and physical absolute-zero validation.
Temperature conversions run in your browser. Entered and converted values are not placed in the URL or analytics.
How to use this tool
Enter a finite temperature, choose the source and destination scales, and swap direction when needed. The converter accepts negative Celsius and Fahrenheit values but rejects any temperature below physical absolute zero.
Transparent method
Formula and method
Fahrenheit = (Celsius × 9/5) + 32. Celsius = (Fahrenheit − 32) × 5/9. Kelvin = Celsius + 273.15. Celsius = Kelvin − 273.15. Other pairs convert through canonical Celsius without rounding intermediate values.
Worked examples
- 0 °C = 32 °F = 273.15 K.
- 100 °C = 212 °F = 373.15 K.
- −40 °C = −40 °F = 233.15 K.
- Absolute zero is 0 K = −273.15 °C = −459.67 °F.
- 37 °C = 98.6 °F = 310.15 K; this is a conversion example, not medical guidance or an assessment of an individual's temperature.
Assumptions and limits
- Celsius is the canonical internal scale; Fahrenheit and Kelvin convert through Celsius.
- Absolute zero is exactly 0 K, equivalent to −273.15 °C and −459.67 °F under these scale relationships.
- Values below absolute zero are rejected in every source scale, while absolute zero itself is valid.
- The engine keeps full JavaScript number precision internally and rounds only the displayed representation.
- Water reference points depend on pressure and other conditions; the boiling example assumes standard atmospheric pressure.
- The 37 °C row is only a familiar conversion example and is not medical advice, diagnosis or an individual health threshold.
Celsius vs Fahrenheit
Celsius and Fahrenheit use different interval sizes and different zero points. Water freezes at 0 °C or 32 °F under the stated reference conditions, while a change of 1 °C equals a change of 1.8 °F.
Because the scales have offsets, temperature cannot be handled by the Unit Converter's factor-only multiplication model. This focused converter applies an affine formula and uses Celsius as its canonical internal scale.
Celsius to Fahrenheit formula
Multiply Celsius by 9/5, then add 32: °F = (°C × 9/5) + 32. For example, 20 °C converts to 68 °F.
Fahrenheit to Celsius formula
Subtract 32 from Fahrenheit, then multiply by 5/9: °C = (°F − 32) × 5/9. For example, 68 °F converts to 20 °C.
Kelvin conversion
Kelvin uses the same interval size as Celsius but begins at absolute zero. Add 273.15 to Celsius to get Kelvin, or subtract 273.15 from Kelvin to get Celsius.
The kelvin symbol is K without a degree sign. Fahrenheit-to-Kelvin and Kelvin-to-Fahrenheit conversions pass through canonical Celsius so the engine maintains one implementation of each scale relationship.
Absolute zero
Absolute zero is the physical lower bound of the temperature scales supported here: 0 K, −273.15 °C or −459.67 °F. The converter accepts those boundary values and rejects lower inputs rather than presenting a physically invalid result.
Common reference temperatures
The table shows familiar reference points generated by the same conversion engine. Water freezing and boiling values depend on the stated conditions, room examples are illustrative, and the body-temperature row is a conversion example only—not medical guidance.
Rounding temperature results
The engine does not round intermediate Celsius values. The interface displays up to 12 significant digits so exact reference points remain clear while long floating-point tails do not obscure the result.
Common temperature conversion mistakes
Do not apply only a multiplication factor to Celsius and Fahrenheit: their zero points differ. Apply the offset in the correct order, keep the kelvin symbol free of a degree sign, and do not enter a value below the absolute-zero boundary for the chosen scale.
Common temperature conversion table
Reference values generated at build time by the same affine temperature engine used by the calculator.
| Reference | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | -273.15 °C | -459.67 °F | 0 K |
| Water freezing | 0 °C | 32 °F | 273.15 K |
| Cool room example | 18 °C | 64.4 °F | 291.15 K |
| Room temperature example | 20 °C | 68 °F | 293.15 K |
| Warm room example | 25 °C | 77 °F | 298.15 K |
| Body-temperature conversion example | 37 °C | 98.6 °F | 310.15 K |
| Water boiling at standard atmospheric pressure | 100 °C | 212 °F | 373.15 K |
Sources
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply Celsius by 9/5, then add 32. For example, 20 °C equals 68 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32 from Fahrenheit, then multiply by 5/9. For example, 68 °F equals 20 °C.
What is 0 Celsius in Fahrenheit?
0 °C equals 32 °F and 273.15 K.
At what temperature are Celsius and Fahrenheit equal?
−40 °C and −40 °F represent the same temperature.
How do I convert Celsius to Kelvin?
Add 273.15 to the Celsius value. For example, 0 °C equals 273.15 K.
How do I convert Kelvin to Celsius?
Subtract 273.15 from Kelvin. For example, 273.15 K equals 0 °C.
Can Kelvin be negative?
No. This converter rejects Kelvin values below 0 K because 0 K is absolute zero, the lower physical boundary of the supported scales.
What is absolute zero in each scale?
Absolute zero is 0 K, −273.15 °C and −459.67 °F.
Does the temperature converter round results?
The engine does not round intermediate values. The display uses up to 12 significant digits to limit distracting floating-point noise.
Is the body-temperature example medical guidance?
No. It is included only to demonstrate conversion between temperature scales and does not assess symptoms, diagnosis or individual health.