Temperature Conversion

Convert temperature between 8 scales from any input instantly.

Supports Celsius, Fahrenheit, kelvin, Rankine, Delisle, Newton, Réaumur and Rømer with 0 K validation.

Updated August 22, 2026

CreatorFrank Zhao

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Introduction

This Temperature Conversion calculator converts instantly among eight scales: Celsius, Fahrenheit, kelvin, Rankine, Delisle, Newton, Réaumur and Rømer. Edit any field and the others update automatically — a practical benefit over looking up a one-way table. It is handy whenever you compare lab, kitchen, HVAC or historical records measured in different units.

Lab & study

Switch between °C and K without re-typing, or check an older paper that used Réaumur or Rømer.

Kitchen & HVAC

US recipes in °F next to EU ovens in °C — see both at once.

Travel & weather

Interpret forecasts or equipment specs when the unit changes across borders.

All eight values are shown together under Temperature Scales. You never need to pick a “direction” first.

How to use — quick start

Enter a value in any scale

Type into Celsius, Fahrenheit, kelvin, Rankine, Delisle, Newton, Réaumur or Rømer. Use decimals and a minus sign where needed.

Read the other seven instantly

The remaining fields fill as derived values. Clear any field to start a new conversion.

Check the 0 K boundary if needed

Values colder than absolute zero keep their text but show a red error. Correct the input to restore all conversions.

Worked example — 25 °C

Type 25 into Temperature in Celsius. The calculator shows:

^{\circ}\!F = 1.8 \times 25 + 32

=

77

K = 25 + 273.15

=

298.15

^{\circ}\!De = 150 - 1.5 \times 25

=

112.5

Similarly $^{\circ}\!N = 8.25,\; ^{\circ}\!R\acute{e}=20,\; ^{\circ}\!R\o \approx 20.6,\; ^{\circ}\!R \approx 536.67$ . Entering 77 in Fahrenheit instead would derive the same set — every scale can be the starting point.

Real-world examples

Boiling point check — 100 °C

A student verifies the familiar reference:

K = 100 + 273.15

=

373.15

Also $212\,^{\circ}\!F,\; 671.67\,^{\circ}\!R,\; 0\,^{\circ}\!De,\; 33\,^{\circ}\!N,\; 80\,^{\circ}\!R\acute{e},\; 60\,^{\circ}\!R\o$ — useful when a textbook tables water at 0 °De or 80 °Ré.

Fahrenheit recipe — 350 °F

An oven preset must be set on a °C dial:

^{\circ}\!C = (350-32)/1.8

=

176.67

The guide value $K \approx 449.82$ also matches energy calculations that require kelvin.

Calculation method

Every relation is a linear (affine) mapping with Celsius as the hub: each scale is $y = slope \times ^{\circ}\!C + intercept$ . Because affine maps are exactly invertible, any field can drive the rest.

^{\circ}\!F = 1.8\,^{\circ}\!C + 32

K =\,^{\circ}\!C + 273.15

^{\circ}\!R = 1.8\,^{\circ}\!C + 491.67

^{\circ}\!De = 150 - 1.5\,^{\circ}\!C

^{\circ}\!N = 0.33\,^{\circ}\!C

^{\circ}\!R\acute{e}=0.8\,^{\circ}\!C

^{\circ}\!R\o = 0.525\,^{\circ}\!C + 7.5

Slopes and intercepts match the definitions used in the calculator runtime (Celsius → target).

Why Celsius as hub?

All other scales connect in one step, so the full set stays consistent. Any input recomputes the other seven through the same seven relations — no duplicated logic.

Supported directions

Every pair is reversible: $^{\circ}\!C = (^{\circ}\!F-32)/1.8$ , $^{\circ}\!C = K-273.15$ , $^{\circ}\!C = (150-^{\circ}\!De)/1.5$ , etc.

Other converters on the site covering narrower ranges use the same affine idea. For length or area, see the length converter and area converter.

Tips & best practices

Start from the scale you actually measured

Avoid manual pre-conversion — it adds rounding. Type the observed value directly and let the other seven derive.

Delisle runs backwards

$^{\circ}\!De$ is 0 at boiling and rises as it gets colder — so 600 °De is not “very hot”, it is below absolute zero and will flag red.

Watch the minus sign

$-40\,^{\circ}\!C = -40\,^{\circ}\!F$ is the only point where the two coincide — a handy sanity check.

Use kelvin for science

Thermodynamic and gas-law formulas expect absolute temperature — convert to K first.

Frequently Asked Questions

Can I really convert starting from any scale?

Yes. Edit any of the eight fields; the other seven recompute immediately. No mode or direction switch is needed.

Why does a value below absolute zero stay visible but turn red?

The display keeps your text so nothing is lost, but the field is marked invalid and derived values are paused until you correct it. The boundaries are $-273.15\,^{\circ}\!C,\ -459.67\,^{\circ}\!F,\ 0\,K,\ 0\,^{\circ}\!R,\ 559.725\,^{\circ}\!De$ and the corresponding limits for Newton, Réaumur and Rømer.

Is 0 °De hot or cold?

Hot. Delisle is defined as $^{\circ}\!De = 150 - 1.5\,^{\circ}\!C$ , so 0 °De is boiling water and 150 °De is 0 °C. Smaller Delisle means hotter.

Limitations & Disclaimers

•This is a pure unit conversion. It does not model material properties, heat capacity, or sensor calibration.
•Absolute-zero checks are mathematical. Exotic systems with effective negative absolute temperatures are not represented.
•Display may round long decimals; values remain computed at full working precision.

Next step: For other units try the conversion calculator, length converter or area converter.

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