# Temperature Converter — Celsius, Fahrenheit, Kelvin & Rankine

> Convert between °C, °F, K and °Rankine all at once, with a visual thermometer marking freezing, body temperature, boiling and oven heat. Free and instant.

- **Category:** Conversions & Units
- **Interactive calculator:** https://youcalc.com/en/conversions-units/temperature-converter/
- **Price:** Free, no sign-up required

## Overview

Convert any temperature between Celsius, Fahrenheit, Kelvin and Rankine in one step. Type your value, pick the source scale, and all four results update instantly — useful for cooking, science, weather, and engineering.

## How to read your result

The four result cards show the equivalent temperature in each scale simultaneously. The visual thermometer marks key reference points — freezing (0 °C / 32 °F), normal body temperature (37 °C / 98.6 °F), boiling (100 °C / 212 °F) and a hot oven — so you can place your value in everyday context.

## Method

All conversions route through Celsius as the internal pivot. From Celsius: Fahrenheit = C × 9/5 + 32; Kelvin = C + 273.15; Rankine = (C + 273.15) × 9/5. To convert from another scale, invert the formula to obtain Celsius first — for example, from Fahrenheit: C = (F − 32) × 5/9; from Kelvin: C = K − 273.15; from Rankine: C = (R − 491.67) × 5/9. Kelvin is the SI base unit for thermodynamic temperature; its zero point is absolute zero. The offsets 273.15 and 491.67 are exact by definition under the International System of Units.

## Example

- **Setup:** Enter 100 °C (the boiling point of water at sea level) as the input.
- **Result:** The converter returns 212 °F, 373.15 K and 671.67 °R — confirming that water boils at the same physical point on every scale.

## Frequently asked questions

### What is absolute zero, and why does it matter?

Absolute zero (0 K / −273.15 °C / −459.67 °F) is the lowest possible temperature, where molecular motion effectively stops. Kelvin starts there, making it the natural unit for thermodynamic calculations. No value below 0 K is physically possible.

### Why does the United States still use Fahrenheit?

Fahrenheit was the dominant scale in English-speaking countries before Celsius was standardised in the 19th century. The US never adopted the metric system for everyday use, so Fahrenheit persisted in weather forecasts and household contexts, even as science uses Celsius and Kelvin worldwide.

### When would I need Rankine?

Rankine (°R) is an absolute scale based on Fahrenheit degrees. It is mainly used in some branches of American engineering thermodynamics — for example, steam tables and aerospace calculations written for US customary units — where an absolute scale is needed but Fahrenheit degree intervals are preferred.

### How do I convert Fahrenheit to Celsius mentally?

A quick approximation: subtract 32, then halve the result. For example, 68 °F − 32 = 36 ÷ 2 = 18 °C (exact value is 20 °C, so this is close enough for rough estimates). For exact results, use the formula °C = (°F − 32) × 5/9.

### Is there a temperature where Celsius and Fahrenheit are equal?

Yes — at −40 degrees. Both scales read −40 at the same physical temperature, which is a convenient calibration checkpoint often cited in cold-climate discussions.

## Related calculators

- [Unit Converter](https://youcalc.com/en/conversions-units/unit-converter/)
- [Fuel Economy Converter](https://youcalc.com/en/conversions-units/fuel-economy-converter/)

## Sources

- https://www.nist.gov/si-redefinition/kelvin-introduction
- https://www.bipm.org/en/publications/si-brochure

---

Interactive version: https://youcalc.com/en/conversions-units/temperature-converter/ · From YouCalc — https://youcalc.com