Double to decimal not converting and rounding

Question

What is the best way to round double to two decimal places?

For example, I want to convert

3.45345323423423E+28

to

3.45

I have tried Math.Round(3.45345323423423E+28,2)..but its not working — user2691432, Dec 31 '13 at 09:42
Convert it in output, formate it with the `.ToString(string);` function. — Jite, Dec 31 '13 at 09:42
Erm, are you use that you want to convert `3.45345323423423E+28` to `3.45`? There are quite some numbers in between and the difference between those decimals is huge :-) — Darin Dimitrov, Dec 31 '13 at 09:42
I have done :- double doubl = Math.Round(3.45345323423423E+28,2); doubl.ToString("0.00") — user2691432, Dec 31 '13 at 09:43
As far as I'm aware, 3.45345323423423E+28 is actually 34534532342342300000000000000, so... you can't display that as 3.45, because it's... slightly larger than 3.45... — Pete Ebdon, Dec 31 '13 at 09:51

score 7 · Accepted Answer · edited May 23 '17 at 11:56

7

You are aware that 3.45345323423423E+28 is a pretty large number and does not contain a decimal part?

(Stripping the scientific notation, your number is 34,534,532,342,342,300,000,000,000,000 which is, of course, an integer).

If you want to round a number to 2 decimal places then use Math.Round(value, 2); But do be aware that your example number will not be changed.

If however, you want to round to 2 significant figures, then see this answer: Round a double to x significant figures

edited May 23 '17 at 11:56

Community

1
1

answered Dec 31 '13 at 09:47

Bathsheba

231,907
34
361
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Ok you are saying that this number does not contain a decimal part..rather it is merely a representation of a large number ? – user2691432 Dec 31 '13 at 10:01
2

Do you know what the "E+28" part of the number means? – NWard Dec 31 '13 at 10:09

score 1 · Answer 2 · edited Dec 31 '13 at 09:45

1

use Math.round

Math.Round (value, 2);

Rounds a number to a specified number of fractional digits double-precision floating-point value.

edited Dec 31 '13 at 09:45

Bathsheba

231,907
34
361
483

answered Dec 31 '13 at 09:42

Nagaraj S

13,316
6
32
53

score 1 · Answer 3 · edited Dec 31 '13 at 09:51

1

Use this:

Math.Round(value, 2);

This will round up your value to 2 decimal places.

Store it in some variable or display it.

edited Dec 31 '13 at 09:51

BartoszKP

34,786
15
102
130

answered Dec 31 '13 at 09:43

Ashish

1,856
18
30

It is giving me same output as 3.45345323423423E+28 – user2691432 Dec 31 '13 at 09:46
If going out of way add `0.005` to number and convert to string via `variable.toString()` later take substring of 4 places from left and convert back to int by `parseInt` this will give you rounded value – Ashish Dec 31 '13 at 09:52

Ehsan · Answer 4 · 2013-12-31T09:52:15.213

1

First of all you should consider using some other data type for such large number. Perhaps decimal. Because precision of double is only up to 15-16 digits.

If you still persist with double then you can use Math.Round here.

double db = 3.45345323423423E+28;
db = Math.Round(db, 2);

However, if you change your mind to switch to decimal then following should do the trick.

decimal d = 3.45345323423423E+28m;
d = decimal.Round(d, 2);

edited Dec 31 '13 at 09:52

answered Dec 31 '13 at 09:44

Ehsan

31,833
6
56
65

It is also giving me same output as 3.45345323423423E+28 – user2691432 Dec 31 '13 at 09:47

score 0 · Answer 5 · answered Dec 31 '13 at 10:14

0

I think you want to display it like this: 3.45E+28

Then you should do something like this:

double number = 3.45345323423423E+28;
string result = number.ToString("0.00E+00");

Hope this will help you in your quest.

answered Dec 31 '13 at 10:14

Casperah

4,504
1
19
13

Double to decimal not converting and rounding

5 Answers5