### Math Constants in JavaScript: Math.E, Math.PI, and more JavaScript FAQ | JavaScript Numbers FAQ

Question: How do I handle mathematical constants in JavaScript?

Answer: In JavaScript, some mathematical constants are predefined – they are properties of the `Math` object. You can write these constants as follows:

```Math.PI      // pi = 3.14159265...
Math.E       // e = 2.71828182...
Math.LOG2E   // log of e base 2
Math.LOG10E  // log of e base 10
Math.LN2     // log of 2 base e
Math.LN10    // log of 10 base e
Math.SQRT2   // square root of 2
Math.SQRT1_2 // square root of 1/2```
Thus, there is no need to remember the exact value of e or π. Just use `Math.E` or `Math.PI`! Here is a simple code example that computes the radius of the Earth in kilometers and in miles using `Math.PI`:
```var rkm = 20000/Math.PI;
var rmi = 20000/(1.609344*Math.PI);

document.write(
"The Earth's radius is "
+rkm.toFixed()+" km, or "
+rmi.toFixed()+" miles. "
);
```
This code produces the following output:
```
var rkm = 20000/Math.PI;
var rmi = 20000/(1.609344*Math.PI);

document.write(
"The Earth's radius is "
+rkm.toFixed()+" km, or "
+rmi.toFixed()+" miles. "
);
```

See also:

• JavaScript number literals aka constants
• Math functions in JavaScript
• Can I display mathematical symbols as part of JavaScript output?
• Can I display Greek letters on my page as part of JavaScript output?
• Accuracy of JavaScript computations
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