These are not so much calculation errors as input and display errors. Most decimal fractions cannot be represented exactly in a fixed number of binary digits, so data entered cannot be represented exactly internally. Calculations can also have rounding errors. Almost all calculators suffer from this to some extent. When numbers are very big or very small, it is better to display them in floating point format. There may also be a case for rounding very small numbers to zero. Money sums involving …dollars and cents always cause problems unless the calculator has a special mode that works in integer cents. The problems mentioned below are essentially display issues. More

Thanks for all your comments! Sorry about the problem with precision issue, but it's a limitation in Javascript's built-in math library. Javascript uses binary floating point to store decimal numbers which in some cases cannot be represented exactly as finite precision binary floating point numbers.

try to calculate this:
80.57 - 50 - 30.57
The result should be 0
It is -1.220703125

Sorry, but your calculator have a bug (is there a intel inside?)

Try to calc 80.57 - 50 = ?

.... and you get 30.5699999

Sorry, but a calculator what can't do right calculations is totally useless, no matter how much it is skinnable .

I agree with Penny, miniCalc will go into my list of "must have" widgets