Number Base Converter
Convert numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36. Uses BigInt arithmetic, so numbers of any length convert without losing precision.
0-9A-Z. Grouping inserts underscores for readability — binary in groups of 4, hex in groups of 4, octal in groups of 3. This is a display convenience only, not part of the value. Fractional numbers are not supported.
Finding This Number Base Converter Useful?
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Get the Standalone VersionWhat Is a Number Base Converter?
A Number Base Converter translates a number written in one positional numeral system into another. The most common bases in computing are binary (2), octal (8), decimal (10) and hexadecimal (16), but any integer base from 2 up to 36 is meaningful — the digits simply run out of familiar symbols past 10, so letters A through Z are used for the values 10 through 35. This tool reads your input in whichever base you specify and shows the same numeric value in every common base at once. It uses BigInt arithmetic internally, so even very large values convert with full precision.
Key Features
Arbitrary Precision
Uses BigInt, so a 100-digit number converts with exact accuracy. No floating-point rounding, no scientific notation, no lost digits.
Every Common Base at Once
Binary, octal, decimal and hexadecimal are always shown. Add a custom base to see it alongside them.
Copy Any Value
Each result has its own copy button, plus a Copy All option for pasting the whole set into notes or documentation.
Digit Grouping
Readable grouping for binary (4s), octal (3s) and hex (4s). Toggle it on and off as you prefer.
Bit & Byte Stats
See how many bits, bytes and decimal digits the value needs — useful when working out how a number will fit in a register or field.
Nothing Leaves Your Browser
No server, no analytics, no logging. All conversion happens in JavaScript running on your device.
How to Use the Number Base Converter
- Type or paste a number into the input field. Spaces and underscores are ignored, so you can copy formatted values in directly.
- Pick the source base — binary, octal, decimal, hexadecimal, or a custom base from 2 to 36.
- Read the results — all four common bases are shown immediately, along with your custom base if you have set one.
- Copy what you need — use the copy button on any single result, or Copy all values for the whole set.
- Toggle digit grouping if you want cleaner binary or hex output, or leave it off for a raw run of characters.
Practical Use Cases
Debugging Bitmasks
See what 0xFF00FF00 is in binary and decimal without reaching for a calculator.
Working with Hashes
Convert hex fragments into decimal to compare with other representations.
Learning Number Systems
Understand how the same value looks in different bases, and how negative numbers are written.
Low-Level Programming
Quickly convert between bases when writing assembly, embedded code, or hardware drivers.
Cryptography
Move between decimal and hex representations of large integers used in RSA and ECC work.
Data Encoding
Base-36 and base-32 values appear in URL shorteners, ID generators and user-facing tokens.
Important Notes and Limitations
A few honest caveats:
• Integers only. Fractional numbers such as 3.14 or 0.001 are not supported, because converting them between bases requires deciding on a precision, and the answer depends on that choice. This tool handles whole numbers only.
• No two’s-complement display. Negative numbers are shown with a minus sign. If you need to see how a negative value is represented in two’s-complement, work out the positive magnitude first, then apply the encoding yourself — that is a decision about a fixed bit width, and this tool is width-agnostic.
• Digits are upper-case letters for bases above 10. The value for 15 in hex is F, not f, in the output. Lower-case input is accepted and converted automatically, so you can paste deadbeef and it will work fine.
• Very large numbers may slow the input field. A value with several thousand digits is fine for the conversion, but the text input itself may feel sluggish when editing. The calculations themselves stay fast.
• Grouping is cosmetic. Underscores inserted between digit groups are for readability only. If you copy a grouped value and paste it back into the input, the underscores are stripped before parsing.
Frequently Asked Questions
Any number that fits in your browser’s memory. The converter uses BigInt, which is JavaScript’s arbitrary-precision integer type. A 500-digit number is fine; a 500,000-digit number will convert but may make the input field feel slow to edit. There is no fixed limit.
Because we only have ten familiar symbols (0–9), but base 11 needs 11 distinct digits and base 36 needs 36. The standard convention, adopted by nearly every programming language, is to use the letters A through Z for the values 10 through 35. So base 16 uses 0-9A-F, base 32 uses 0-9A-V, and base 36 uses 0-9A-Z.
Fractional numbers in one base rarely have a finite representation in another. The decimal fraction 0.1, for example, is 0.0001100110011... in binary — it never terminates. Any answer requires deciding how many binary digits of precision to keep, and the correct choice depends on the application. To keep the tool unambiguous, only integers are supported.
They are conventions used in source code and documentation to make the base explicit: 0x for hexadecimal, 0b for binary, 0o for octal. This tool does not require them — you select the base with the buttons — but you can paste a value that includes one, and the tool will strip the prefix automatically if you choose the matching base.
No. The whole tool runs in JavaScript in your browser. There is no network request, no analytics, and no logging. You can verify this by opening your browser’s network panel while using the tool — nothing is sent. The standalone edition works completely offline.
About the Author — GenieDevs
Get the Standalone Version
Number Base Converter — Standalone Edition
One self-contained HTML file with the full converter inside. Keep it on your machine, run it from a USB stick, or use it on an air-gapped computer — no internet connection needed.
Final Takeaway
Number base conversions come up constantly when working close to the machine — inspecting a bitmask, reading a memory dump, understanding how an ID is encoded. This tool makes those conversions fast and reliable: type a value in any base from 2 to 36, see the same number in all the common bases at once, and copy the representation you need. It handles arbitrarily large numbers with full precision, so nothing is lost to floating-point rounding, and it runs entirely in your browser without sending a byte.