What is hexadecimal (base 16)?

Hexadecimal uses digits 0–9 and letters A–F. It is commonly used to represent binary data compactly. One hex digit represents 4 bits. For example, decimal 255 = hex FF.

What is octal (base 8)?

Octal uses digits 0–7. It was historically used in computing and is still used for Unix file permissions (chmod 755, chmod 644).

How do I convert hex to decimal in JavaScript?

Use parseInt('ff', 16) — pass the hex string and base 16. To convert decimal to hex, use (255).toString(16). Prefix hex literals with 0x in code: 0xFF === 255.

Number Base Converter — Binary, Decimal, Hex, Octal

Number Base Reference

Decimal	Binary (2)	Hex (16)	Octal (8)
0	0	0	0
10	1010	A	12
15	1111	F	17
16	10000	10	20
255	11111111	FF	377
256	100000000	100	400

How to Use It

Open the tool

Go to Numbers & Dates and scroll to the Number Base Converter.

Type in any field

Enter your number in any base — decimal, binary (0s and 1s only), hex (0–9, A–F) or octal (0–7).

View all results

All other base representations update instantly.

Copy your value

Click the copy button next to the base you need.

Pro Tips

💡In JavaScript: parseInt('FF', 16) converts hex to decimal. (255).toString(16) converts decimal to hex. (255).toString(2) converts to binary.

💡Hex literals in code use 0x prefix: 0xFF === 255. Binary literals use 0b: 0b1111 === 15.

💡Unix file permissions use octal: chmod 755 = owner rwx (7), group rx (5), others rx (5).

Frequently Asked Questions

What is binary (base 2)?

Uses only 0 and 1. Each digit is a power of 2. Decimal 10 = binary 1010 (8+2). The fundamental number system used by all digital computers.

What is hexadecimal?

Uses 0–9 and A–F (16 digits). One hex digit = 4 bits. Decimal 255 = FF. Widely used for color codes, memory addresses and encoding.

What is octal used for?

Unix file permissions. chmod 755 sets rwx for owner, rx for group and others. Octal digits 0–7 each represent 3 bits.

How do I convert in JavaScript?

parseInt('ff', 16) → 255. (255).toString(16) → "ff". parseInt('1010', 2) → 10. (10).toString(2) → "1010".

Convert number bases now

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