# Temperature Converter

- **URL:** https://codeasystem.com/calculators/conversion/temperature-converter/
- **Category:** conversion
- **Description:** Convert temperatures exactly between Celsius, Fahrenheit and Kelvin using the official formulas, with absolute-zero validation built in.
- **Primary output:** Conversion: 100 °F = 37.77778 °C

## Inputs
- Value (name: `value`, type: number, example: 1)
- From (name: `from`, type: select)
- To (name: `to`, type: select)

## Outputs
- Conversion: 100 °F = 37.77778 °C
- In K: 310.92778

## Formula / methodology
```
°C = (°F − 32) × 5⁄9     °C = K − 273.15
°F = °C × 9⁄5 + 32       K = °C + 273.15
```

Unlike other families, temperature scales do not share a zero point, so simple ratios fail. Every conversion routes through Celsius with the exact offset-and-scale formulas above, and any result below absolute zero (−273.15 °C) is rejected as physically impossible.

## Assumptions & limitations
- Results are rounded only for display; full precision is used internally.
- Conversions use exact standard definitions of each unit.

## How to use
1. **Enter the temperature**; Negative values are fine; anything below absolute zero is refused deliberately.
2. **Choose the scales**; Select Celsius, Fahrenheit or Kelvin for both sides.
3. **See all three**; The output shows your target scale plus the remaining scale as context.

## Example
A classic fever check: 100 °F converts to roughly 37.78 °C.

Result for these inputs:

```
Conversion: 100 °F = 37.77778 °C
```

## About this calculator
### Why −40 is famous

At exactly −40 degrees the two civilian scales agree: (−40 × 9⁄5) + 32 = −40. It is the only crossover point and a handy sanity check whenever a conversion looks suspicious.

### Kelvin is not just fancy Celsius

Kelvin starts at absolute zero, making it the natural scale for physics: gas laws and thermal radiation depend directly on absolute temperature. Room temperature near 293 K sounds exotic but is simply 20 °C.

### Fever thresholds across scales

Normal body temperature hovers near 37.0 °C / 98.6 °F, and clinicians generally flag readings above 38.0 °C / 100.4 °F. Quick conversion matters when reading advice written for another country’s scale.

## FAQs
### Can I enter negative temperatures?

Yes, down to absolute zero. Below −273.15 °C (−459.67 °F, 0 K) the calculator refuses because no colder temperature exists.

### Which countries use Fahrenheit?

Principally the United States, its territories and a handful of Caribbean nations; almost everywhere else reports weather in Celsius.

### Does wind chill convert?

No; wind chill is an index computed from temperature plus wind speed, not a true temperature. Convert the underlying air temperature instead.

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Last updated: 2026-08-23 · Version: 1.0.0 · [HTML version](https://codeasystem.com/calculators/conversion/temperature-converter/)