Converting float to string and getting exact value

Question

This is follow up for my last question about converting string to float

I have this value stored in a float variable: 33.9112625 (it's thirty three) and I need to convert it to string and get the exact value but I'm unable to do so. float.ToString( CultureInfo.InvariantCulture) gives me "33.91126" as result. I tried .ToString("G"), "G7" and CultureInfo.InvariantCulture.NumberFormat but they didn't help. How can I convert a float to string and get the exact same value?

If you want exact values, floats are a really bad choice for a data type. — Mark Byers
– Mark Byers, Commented Feb 15, 2010 at 21:29
If you want exact decimal representations, you should be using Decimals. — recursive
– recursive, Commented Feb 15, 2010 at 21:39
The float type can only reliably store 7 significant digits. You'll never get the last two digits in that number. — Hans Passant
– Hans Passant, Commented Feb 16, 2010 at 3:40

Lord Darth Vader · Accepted Answer · 2023-02-08 15:10:11Z

8

First, you aren't saving "exact" values in a float (System.Single). For details, see David Goldberg's article on floating point precision.

That being said, if you want to convert this, you'll need to specify extra precision to Single.ToString(). By using "G", you get the default precision, which is 7. In your case, to see the value you've shown, you'd need 9, so you could use "G9".

edited Feb 8, 2023 at 15:10

Lord Darth Vader

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answered Feb 15, 2010 at 21:29

Reed Copsey

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Eric J. · Accepted Answer · 2023-02-07 19:43:29Z

5

Jon Skeet provides an article explaining this along with C# code to print the exact representation.

edited Feb 7, 2023 at 19:43

answered Feb 15, 2010 at 21:31

Eric J.

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1 Comment

mskfisher Over a year ago

Could you provide a summary of the article in case it expires?

t0mm13b · Accepted Answer · 2010-02-15 21:39:06Z

1

Try changing it to Decimal type, I tried it using float but it would only show 5 decimal places.

decimal d = 33.9112625M;
Console.WriteLine("{0}", d.ToString(System.Globalization.InvariantCulture));

Hope this helps, Best regards, Tom.

answered Feb 15, 2010 at 21:39

t0mm13b

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1 Comment

t0mm13b Over a year ago

At least it would be favourable to put a comment in as to why it was downvoted? Ignorant...you'd do the exact same thing I'm sure if you cared enough to improve yourself!

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