How to Estimate Celsius Temperatures in Fahrenheit

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Most countries use Celsius as a unit of measurement for calculating the temperature. Many online applications will precisely convert Celsius into Fahrenheit but if you don’t have access to the Internet, use the following techniques to give you a good estimate.

Method 1
Method 1 of 3:

Estimating an Approximate Temperature

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  1. Look for a temperature display. Many public clocks display the temperature below the time. Ask someone to tell you the temperature if you cannot locate a thermometer or temperature display.
  2. Use a calculator or simply multiply the numbers in your head. Either way, you want to double this number.
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  3. Take the doubled number and add 30 to it. Make use of a calculator or perform the addition in your head. This will give you an approximate temperature in Fahrenheit. [1] For example:
    • Determine the temperature in Celsius: 20 degrees
    • Multiply this number by two: 20 x 2 = 40
    • Add thirty to this number: 40 + 30 = 70 degrees Fahrenheit
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Method 2
Method 2 of 3:

Estimating a Semi-Precise Temperature

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  1. Find a temperature display. Look for a public clock on a building such as a bank. Many public clocks also display the temperature below the time. Ask someone to tell you the temperature if you cannot locate a thermometer or temperature display.
  2. Use a calculator or simply multiply the numbers in your head. Either way, you want to double this number.
  3. Calculate 10% by multiplying the number by 0.1. For example, 100 x 0.1. = 10. Subtract this number from the number you doubled in the first calculation. Use a calculator to perform these operations for best results.
  4. Take the doubled number and add 32 to it. Make use of a calculator or perform the addition in your head. This will give you a semi-precise temperature in Fahrenheit. [2] For example:
    • Determine the temperature in Celsius: 20 degrees
    • Multiply this number by two: 20 x 2 = 40
    • Determine ten percent of this number: 40 x 0.1 = 4
    • Subtract this number from your number in step two: 40 – 4 = 36
    • Add thirty-two to this number: 36 + 32 = 68 degrees Fahrenheit
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Method 3
Method 3 of 3:

Memorizing Key Numbers

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  1. These numbers are easy to memorize and will allow you to make quick conversions. Memorize Celsius to Fahrenheit using multiples of 10:
    • 0 degrees Celsius equals 32 degrees Fahrenheit.
    • 10 degrees Celsius equals 50 degrees Fahrenheit.
    • 20 degrees Celsius equals 68 degrees Fahrenheit.
    • 30 degrees Celsius equals 86 degrees Fahrenheit.
    • 40 degrees Celsius equals 104 degrees Fahrenheit.
  2. These numbers are fairly easy to memorize and will allow you to make precise conversions. Memorize Celsius to Fahrenheit using multiples of 5:
    • -5 degrees Celsius equals 23 degrees Fahrenheit.
    • 5 degrees Celsius equals 41 degrees Fahrenheit.
    • 15 degrees Celsius equals 59 degrees Fahrenheit.
    • 25 degrees Celsius equals 77 degrees Fahrenheit.
    • 35 degrees Celsius equals 95 degrees Fahrenheit.
  3. Memorize Fahrenheit to Celsius using multiples of 10 to perform rough conversions:
    • 32 degrees Fahrenheit equals 0 degrees Celsius.
    • 40 degrees Fahrenheit equals 4.4 degrees Celsius.
    • 50 degrees Fahrenheit equals 10 degrees Celsius.
    • 60 degrees Fahrenheit equals 15.5 degrees Celsius.
    • 70 degrees Fahrenheit equals 21.1 degrees Celsius.
    • 80 degrees Fahrenheit equals 26.6 degrees Celsius. [3]
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Expert Q&A

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  • Question
    Are there any other ways to estimate Celsius to Fahrenheit?
    Dr. Vivek Prakash
    Biomedical Engineer
    Dr. Vivek Prakash is a Biomedical Engineer based in Oxford, Ohio. He works as a Research Associate at Miami University, working on cell-based hormone replacement therapy. He received his PhD from the Department of Biosciences and Bioengineering at the Indian Institute of Technology.
    Dr. Vivek Prakash
    Biomedical Engineer
    Expert Answer
    To estimate Celsius to Fahrenheit without precise calculations, you can use a quick approximation. Simply double the Celsius temperature and add 30. For instance, if it's 20 degrees Celsius, doubling it to 40 and adding 30 gives an estimated Fahrenheit temperature of 70. This provides a rough conversion without the need for precise calculations.
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  • Question
    What's a quick method to convert Celsius to Fahrenheit?
    Donagan
    Top Answerer
    There's only one method. See Convert Celsius (°C) to Fahrenheit (°F) .
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  • Question
    C = 5/9 (F - 32). 113 F - 32 = 81 x 5/9 = 45 C. Is this correct, does 113 Fahrenheit = 45 degrees Celsius?
    Donagan
    Top Answerer
    Yes, that's correct.
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      Warnings

      • The quick method is a good estimate only within a range of temperatures normally felt by the human body. The estimation becomes less accurate the further from this range you go.
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      References

      1. ↑ http://lifehacker.com/5917331/quickly-convert-between-fahrenheit-and-celsius-without-a-calculator
      2. ↑ http://www.aaamath.com/mea414x2.htm
      3. ↑ http://www.asknumbers.com/tables%5Ccelsius_to_fahrenheit_conversion_table.png

      About This Article

      Article Summary X

      To estimate a Celsius temperature in Fahrenheit, multiply the temperature by 2, then add 30 to that number. This will give you an approximate temperature in Fahrenheit. If you need a more precise estimate, multiply the temperature by 2, then subtract 10% and add 32 to that number. The result will more closely represent the Celsius to Fahrenheit conversion. For help memorizing a few Celsius to Fahrenheit conversions, keep reading!

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