Windows Calculator Bug and Its Cause

A bug has been lingering in the calculator application of Windows. Know about the error and the cause behind it.

The calculator tool has been available in all the versions of Microsoft Windows and has been vastly used. However, do you know that there is a bug in Windows calculator?

  1. Open Windows calculator
  2. Write 4 on calculator
  3. Take its square root (sqrt) … 2 will be shown as the answer
  4. Now subtract 2 from the 2 result
  5. Instead of showing 0, the calculator will show 1.068281969439142e-19 in standard mode and  -8.1648465955514287168521180122928e-39 in scientific mode

This error appears whenever you subtract a number from the result of the sqrt of that number. So, it can be reproduced using any number.

Windows calculator bug (shown with number 4)

Windows calculator bug (shown with number 4)


This error is present in all the versions of Windows. The calculator application comes bundled with Windows.

Cause of Calculator Bug

The root cause of this error lies in the order of operations you do and how calculator handles them. Take the following sequence of operation:

  1. Start the calculator
  2. Key press 4
  3. Take it sqrt.  The answer will be 2  (this result remains in calculator’s memory)
  4. Click subtract (now operation in memory is subtract)
  5. Click equals (=)
  6. The calculator will show 0 (which is correct)

When you press equal to button –the calculator repeats the operation in the memory on the value that is there in memory.

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