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Conversions

Rømer to Celsius Converter.

Converts a temperature from the Rømer scale to Celsius. The Rømer scale sets the freezing point of water at 7.5 °Rø and boiling point at 60 °Rø.

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How it works

  1. 1

    Enter the temperature in degrees Rømer.

  2. 2

    Subtract 7.5 from the Rømer value.

  3. 3

    Multiply the result by 40/21 to get Celsius.

  4. 4

    The result is the temperature in degrees Celsius.

(roemer - 7.5) * (40 / 21)

Frequently asked questions

What is the Rømer scale?

The Rømer scale is a temperature scale proposed by Danish astronomer Ole Rømer in 1701. It sets the freezing point of water at 7.5 degrees and the boiling point at 60 degrees.

How do I convert Celsius to Rømer?

Use the inverse formula: Rømer = Celsius * (21/40) + 7.5. For example, 20°C equals 20 * 0.525 + 7.5 = 18 °Rø.

Is the Rømer scale still used today?

No, it is largely obsolete. It is mainly of historical interest, as it influenced the development of the Fahrenheit scale.

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Temperature in Celsius

0°C

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How it works

Converts a temperature from the Rømer scale to Celsius. The Rømer scale sets the freezing point of water at 7.5 °Rø and boiling point at 60 °Rø.

  1. Enter the temperature in degrees Rømer.
  2. Subtract 7.5 from the Rømer value.
  3. Multiply the result by 40/21 to get Celsius.
  4. The result is the temperature in degrees Celsius.

Formulas

The math behind this calculator, written out so you can verify the result.

Rømer to Celsius

°C = (°Rø - 7.5) × 40/21

The Rømer scale has 52.5 degrees between freezing and boiling of water (60 - 7.5), while Celsius has 100 degrees. So each Rømer degree equals 100/52.5 = 40/21 Celsius degrees.

Real-world use cases

Where this calculation shows up in everyday life.

Historical temperature records

Convert old temperature readings recorded in Rømer to modern Celsius for comparison.

Example: A 1700s weather log shows 10 °Rø, which is about 4.76 °C.

Educational demonstrations

Teach students about the evolution of temperature scales and conversions.

Example: Show that 0 °Rø is about -14.29 °C.

Scientific research

When working with historical scientific papers that use Rømer, convert to Celsius for consistency.

Example: Convert 30 °Rø to 42.86 °C.

Tips and common mistakes

Tips

  • Remember the freezing point of water is 7.5 °Rø, not 0.
  • The conversion factor is 40/21 ≈ 1.90476.
  • For quick mental estimates, multiply the Rømer value by 2 and subtract 15 to get approximate Celsius.
  • Use a calculator for precise conversions, especially for non-standard values.

Common Mistakes to Avoid

  • Forgetting to subtract 7.5 before multiplying.
  • Using the wrong conversion factor (e.g., 21/40 instead of 40/21).
  • Confusing Rømer with Réaumur, which has different freezing and boiling points.

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.