Convert.ToSingle() from double in vb.net returns wrong value

Here is my question :

If we have the following value 

0.59144706948010461

and we try to convert it to Single we receive the next value:

0.591447055

As you can see this is not that we should receive. Could you please explain how does this value get created and how can I avoid this situation?

Thank you!

Jon Skeet
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As you can see this is not that we should receive.

Why not? I strongly suspect that's the closest Single value to the Double you've given.

From the documentation for Single, having fixed the typo:

All floating-point numbers have a limited number of significant digits, which also determines how accurately a floating-point value approximates a real number. A Single value has up to 7 decimal digits of precision, although a maximum of 9 digits is maintained internally.

Your Double value is 0.5914471 when limited to 7 significant digits - and so is the Single value you're getting. Your original Double value isn't exactly 0.59144706948010461 either... the exact values of the Double and Single values are:

  • Double: 0.5914470694801046146693579430575482547283172607421875
  • Single: 0.591447055339813232421875

It's important that you understand a bit about how binary floating point works - see my articles on binary floating point and decimal floating point for more background.

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