What's octal used for today?

It was more common in early computing but is less prevalent now than hexadecimal — included here mainly for completeness and specific legacy use.

Is there a limit to how large a number I can convert?

Very large numbers may lose precision due to how JavaScript handles large integers — typical everyday values convert reliably.

How do I convert a fraction or decimal number?

This tool works with whole numbers only — split a decimal into its whole and fractional parts and convert the whole-number portion, since fractional base conversion needs separate handling.

Can I enter lowercase hex digits?

Yes — hex input accepts lowercase or uppercase a-f interchangeably; the underlying parsing is case-insensitive. Only the output hex readout is always displayed in uppercase, regardless of how you typed it.

What happens if I type an invalid digit partway through, like 18 while Base is set to Binary?

It's only flagged as fully invalid if the very first character isn't valid for the selected base. A value like 18 in binary reads just the leading valid digit (1) and silently drops the rest, converting as if you'd entered 1 — so a typo partway through a longer number won't always trigger the error message.

Does it handle negative numbers?

Yes — a leading minus sign is accepted for any base, and negative results display with that same minus sign in every base (binary, octal, hex), not as two's-complement binary notation.

Do leading zeros, like 011 in binary, change the result?

No — leading zeros are ignored and don't change the value or trigger any special interpretation, since the base is always the one you explicitly selected.

Does the Value field restrict which characters I can type based on the selected Base?

No — it's a free text field, not an input mask. You can type any character regardless of the current Base; entering something invalid for that base (like typing letters while Base is Decimal) just shows an inline error rather than blocking the keystroke.

Number Base Converter

About the Number Base Converter

Converts a number between binary, octal, decimal, and hexadecimal at once, showing all four representations of the same value side by side.

100% Free Runs in Your Browser No Sign-Up Required

How to use it

Enter a Value.
Select which Base that value is currently in.
Read all four base representations in the readout.

Formula

Each digit position represents a power of the base: for base b, the digit at position i contributes digit × b^i. Converting re-expresses the same value in a different positional system.

Worked example

Decimal 255 is 11111111 in binary, 377 in octal, and FF in hexadecimal — all four represent the identical quantity.

Decimal 0-15 in each base

Decimal 0-15 in each base
Decimal	Binary	Octal	Hex
0	0000	0	0
1	0001	1	1
2	0010	2	2
4	0100	4	4
8	1000	10	8
10	1010	12	A
15	1111	17	F
16	10000	20	10

Recommendations

• Hexadecimal is common in programming for colors, memory addresses, and byte values, since two hex digits map cleanly to one byte.
• Binary digits group naturally into sets of 4, which is exactly one hex digit — handy for mental conversion between the two.
• Entering digits invalid for the selected base, like an 8 while in binary, will be flagged as invalid.

Frequently asked questions

Hexadecimal is base 16, which needs 16 distinct digits — after 0-9, it continues with A-F to represent values 10 through 15.

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