Temperature Conversion Calculator
Switch instantly between Celsius, Fahrenheit, Kelvin and more
Temperature conversion FAQ
What is the exact relationship between Celsius and Fahrenheit?
Celsius and Fahrenheit are both offset scales. The conversion formula from Celsius to Fahrenheit is °F = (°C × 9/5) + 32. To go back the other way, use °C = (°F − 32) × 5/9. This calculator applies those formulas directly behind the scenes whenever you move between °C and °F.
Why do scientists use Kelvin instead of Celsius?
Kelvin (K) is an absolute temperature scale that starts at absolute zero, where particles have minimal thermal motion. Its size is the same as a Celsius degree, so a change of 1 K equals a change of 1 °C, but 0 K is −273.15 °C. Using Kelvin makes formulas for thermodynamics and statistical mechanics much simpler, which is why it’s the SI base unit for temperature.
What are Rankine, Delisle and Newton degrees?
Rankine (°R) is an absolute scale used mainly in older US engineering work; it mirrors Fahrenheit but with its zero at absolute zero. Delisle (°De) and Newton (°N) are historical scales from early thermometry. They’re much rarer today, but still appear in history-of-science notes and some legacy tables, so this converter keeps them available.
Why is temperature conversion different from length or speed?
Length and speed conversions are usually a simple multiply-by-a-factor job. Temperature scales include both a scale factor and an offset. For example, the difference between 0 °C and 100 °C is the same as between 32 °F and 212 °F, but the zeros are in different places. That’s why the formulas add or subtract constants as well as multiplying.
Can I use this for negative temperatures?
Yes. The calculator handles negative values like −40 °C or −10 °F correctly. Those values are common in weather reports and physics problems. The underlying formulas work the same way for positive and negative numbers.
Is this accurate enough for lab work and engineering?
The formulas are exact based on modern definitions. The result is rounded for display, but the internal calculations keep full precision. For cooking, weather and most classroom problems, the shown precision is more than enough. For high-precision lab measurements, you can treat the output as a convenient cross-check and keep more digits in your own notebook or software.
From oven dials to absolute zero on one page
This temperature conversion calculator is meant to bridge everyday and scientific scales. You can take a weather forecast in °F, convert it to °C for a lab notebook, translate recipes from °C to °F, or move from °C up to Kelvin or Rankine for thermodynamics work. The result box keeps things simple with a clear line such as “68 °F = 20 °C”.
1. Choose the temperature units you need
The dropdowns include the main modern and historical scales:
- Celsius (°C) for weather, everyday room and water temperatures, and much of the world’s cooking.
- Fahrenheit (°F) for US weather, some recipes and older engineering references.
- Kelvin (K) for science, engineering and absolute temperature in formulas.
- Rankine (°R) for older US-based thermodynamics work that uses an absolute scale with Fahrenheit-sized degrees.
- Delisle (°De) and Newton (°N) as historical scales that still show up in some tables and history discussions.
You can convert in any direction: °F to °C, K to °R, °De to K, °N to °C, or any other pair the dropdowns support.
2. Base-unit method: everything through Kelvin
To keep the formulas clean, the calculator routes every conversion through Kelvin (K), which is an absolute scale. Each unit has a pair of formulas: one to go to Kelvin and one to go from Kelvin back to that unit.
For example:
- Celsius ⇄ Kelvin
K = °C + 273.15
°C = K − 273.15 - Fahrenheit ⇄ Kelvin
K = (°F − 32) × 5/9 + 273.15
°F = (K − 273.15) × 9/5 + 32 - Rankine ⇄ Kelvin
K = °R × 5/9
°R = K × 9/5 - Delisle ⇄ Kelvin
°C = 100 − (°De × 2/3)
K = °C + 273.15 = 373.15 − (°De × 2/3) - Newton ⇄ Kelvin
°C = °N × 100/33
K = °C + 273.15 = °N × 100/33 + 273.15
When you hit Convert, the tool turns your input into Kelvin using the first formula pair, then turns that Kelvin value into the target scale using the second pair. That keeps all conversions consistent with modern definitions of each scale.
3. Temperature relationships at a glance
This table summarises some of the most useful relationships so you can sanity-check the calculator or do quick mental conversions when you don’t want to write out the full algebra.
| Starting Unit | Resulting Unit | Relationship |
|---|---|---|
| Everyday temperature scales | ||
| Celsius (°C) | Fahrenheit (°F) | °F = (°C × 9/5) + 32 |
| Fahrenheit (°F) | Celsius (°C) | °C = (°F − 32) × 5/9 |
| Celsius (°C) | Kelvin (K) | K = °C + 273.15 |
| Kelvin (K) | Celsius (°C) | °C = K − 273.15 |
| Absolute and historical scales | ||
| Fahrenheit (°F) | Rankine (°R) | °R = °F + 459.67 |
| Rankine (°R) | Kelvin (K) | K = °R × 5/9 |
| Delisle (°De) | Celsius (°C) | °C = 100 − (°De × 2/3) |
| Newton (°N) | Celsius (°C) | °C = °N × 100/33 |
4. Reading and using the result
The result card stays deliberately simple. If you enter 200 and convert from °C to °F, you’ll see something like “200 °C = 392 °F”. For cooking, you might round that or recognise common landmarks (like 180 °C ≈ 356 °F). For lab or homework use, the exact decimal output lets you keep more digits where they matter, while still having a quick way to move between scales.
Because everything flows through Kelvin with clean formulas, the calculator’s behaviour lines up with standard definitions used in meteorology, chemistry, physics and engineering reference tables.
References and further reading on temperature scales
These resources explain how the main temperature scales are defined and how they relate to each other:
- Celsius — describes the Celsius scale, its modern definition tied to Kelvin and how it relates to Fahrenheit.
- Fahrenheit — covers the Fahrenheit scale, fixed points, and the standard conversion formulas with Celsius and Rankine.
- Kelvin — defines Kelvin as the SI base unit for thermodynamic temperature and explains its relationship to Celsius.
- Rankine scale — explains the absolute Rankine scale and its connection to Fahrenheit and Kelvin.
- Delisle scale — summarises the historical Delisle scale and the formula °C = 100 − (°De × 2/3).
- Newton scale — describes Newton’s temperature scale, where 0 °N is melting ice and 33 °N is boiling water.
For critical lab protocols, calibration work or standards compliance, always double-check important values against your organisation’s official tables or instrumentation manuals before finalising numbers.