Räkna.nu
Tools

Temperature Converter

Quickly convert temperatures between Celsius, Fahrenheit, and Kelvin while seeing all three scales at once.

Frequently asked questions

What’s the difference between Celsius, Fahrenheit, and Kelvin?

Celsius and Fahrenheit are common everyday scales, while Kelvin is an absolute scale used in science. Kelvin starts at absolute zero and has no negative values in physical reality.

Can Kelvin be negative?

No. 0 K is absolute zero, the theoretical lowest temperature. If you enter values that would imply negative Kelvin, double-check the input or scale.

What formulas are used for conversion?

Common formulas are: `F = C * 9/5 + 32`, `C = (F - 32) * 5/9`, and `K = C + 273.15`. The converter applies these consistently.

Why is 32°F equal to 0°C?

Fahrenheit uses a different zero point and degree size. The 32°F offset is part of how the scale was originally defined.

Simple inputs

Pick the scale you know, enter the temperature, and choose the scale you need. The converter keeps everything in sync behind the scenes.

Always see every scale

Even when you target a single scale, the calculator shows Celsius, Fahrenheit, and Kelvin equivalents so you can compare or reuse the number instantly.

Perfect for science and travel

Use it for lab work, cooking, travel planning, or weather comparisons—any time you need to jump between temperature systems.

Temperature conversion: Celsius, Fahrenheit, Kelvin

Temperature scales measure the same physical concept, but they use different zero points and step sizes.

The three common scales

  • Celsius (°C): water freezes at 0°C and boils at 100°C (at normal atmospheric pressure).
  • Fahrenheit (°F): water freezes at 32°F and boils at 212°F.
  • Kelvin (K): an absolute scale used in science. 0 K is absolute zero.

Quick conversion formulas

  • F = C * 9/5 + 32
  • C = (F - 32) * 5/9
  • K = C + 273.15

Common questions

  • Why is 32°F equal to 0°C? Fahrenheit uses a different reference point.
  • Can Kelvin be negative? No. Kelvin starts at absolute zero.

How to use the converter

  1. Choose the input scale.
  2. Enter the temperature value.
  3. Read the converted values in the other scales.

If you’re converting for cooking or weather, rounding to one decimal is usually enough. For scientific work, keep more decimals.

How to read this calculator

These results are meant as guidance. They are based on rules, assumptions, and simplified models that can differ from your exact real-world situation.

Estimate, not a legal decision

Use the result as decision support and planning help. For high-stakes choices, confirm the details with the relevant authority, lender, employer, or adviser.

Methodology

Each calculator uses defined inputs, assumptions, and logic. We explain the broader approach on the methodology page.

Read methodology

Sources and updates

Important calculators should be traceable back to official rules, public guidance, or other clearly stated references.

Read about sources

Related calculators

Roman Numerals

Convert between Arabic numbers and Roman numerals. Supports bi-directional conversion for numbers between 1-3999.

Open converter

Percentage Calculator

Choose whether you need the value of a percentage or the percentage of a value, then get the exact number instantly.

Run calculation

Power converter

Convert between watts, kilowatts, megawatts, horsepower, BTU/h, tons of refrigeration, dBm, and dBW with one input.

Open power converter