Javascript floating point number addition different outputs

Question

Why this will not give the results as expected?

console.log(0.2+0.1); // gives 0.30000000000000004 
console.log(0.2+0.3); // gives 0.5
console.log(0.2+0.5); // gives 0.7
console.log(0.2+0.4); // gives 0.6000000000000001

Why the first and last will not give the results as expected?

[What Every Computer Scientist Should Know About Floating-Point Arithmetic](http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html) — Moritz Roessler, Mar 25 '13 at 12:14
take a look at http://stackoverflow.com/questions/588004/is-javascripts-floating-point-math-broken?rq=1 — Syjin, Mar 25 '13 at 12:14
That's a known problem. Try to use `.toPrecision()` or `.toFixed()` — Michael Sazonov, Mar 25 '13 at 12:15

score 1 · Accepted Answer · edited May 23 '17 at 11:57

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It’s because JavaScript used the IEEE Standard for Binary Floating-Point Arithmetic.

All floating point math is like this and is based on the IEEE 754 standard. JavaScript uses 64-bit floating point representation, which is the same as Java's double.

Can be possible duplicate of Is floating point math broken?

edited May 23 '17 at 11:57

Community

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answered Mar 25 '13 at 12:17

Rohan Kumar

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score 0 · Answer 2 · answered Mar 25 '13 at 12:20

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Try .toFixed() .This method formats a number with a specific number of digits to the right of the decimal.

console.log((0.2 + 0.1).toFixed(1)); // gives 0.3
console.log((0.2 + 0.3).toFixed(1)); // gives 0.5
console.log((0.2 + 0.5).toFixed(1)); // gives 0.7
console.log((0.2 + 0.4).toFixed(1)); // gives 0.6

answered Mar 25 '13 at 12:20

Devang Rathod

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Thanks Devang, I know about `toFixed` method. I wanted to know what is the reason behind this `unexpected result`. – Rohan Kumar Mar 25 '13 at 12:33

Javascript floating point number addition different outputs

2 Answers2