Online number base converter: convert between binary, octal, decimal, hexadecimal, and any radix 2–36, with batch mode and BigInt-safe large integers.
TL;DR: Free online number base converter for bases 2–36 with batch mode and letter-case control. BigInt keeps large integers lossless. Runs locally in your browser, no registration required.
For local tools, open DevTools → Network and search your input — it should not appear in requests.
Usage Guide
Binary, octal, decimal, hexadecimal — four costumes for the same number. Reading memory dumps, configuring netmasks, copying color values or MAC addresses are all base conversion in disguise. This tool converts any bases 2–36, supports batch line-by-line conversion and letter-case control, all lossless via BigInt in the browser.
1. Convert a number
- Paste the value (0x / 0b / 0o prefixes are accepted when they match the selected base).
- Pick the source base: presets 2/8/10/16, or Custom for any radix 2–36 (e.g. Base36 short codes).
- Optionally enable an extra output base and toggle A–Z / a–z; results update instantly with one-click copy.
2. Batch and large integers
- Switch to Batch mode — one value per line (snowflake IDs from logs, hex MAC lists, etc.).
- Bad lines show which digit failed and which alphabet is allowed; other lines still convert.
- Values past JavaScript's safe integer (2^53) are not silently rounded — accumulation uses BigInt digit by digit.
3. Why hexadecimal won
One hex digit maps exactly to 4 binary bits (F = 1111), and one byte is exactly two hex digits — the mathematical reason hex became "the human notation for binary". Memory addresses, hashes and MAC addresses are hex not by aesthetics but because it aligns with byte boundaries.
4. Two frequent traps
- JavaScript parseInt(x) without a radix parsed "08" as octal 0 in old engines — always write parseInt(x, 10). This tool takes an explicit base, no ambiguity.
- Integers only: a decimal point or embedded whitespace is rejected with a positioned digit error. IEEE 754 bit patterns are a different problem — use a float bit viewer, not a base converter.
5. Prefixes, casing, and things that only look like hex
- 0b / 0o / 0x are accepted when they match the selected source base; reading decimal 10 as hex (or the reverse) is the most common log-triage misread.
- Hex letters are case-insensitive for value; the output case toggle exists so you can match APIs that mandate lowercase.
- Color literals #FF5733 and MAC AA:BB:CC carry separators — strip # and colons first; this tool converts bare digit strings, not decorated literals.
- Batch mode is per-line: one bad line does not block the rest, and errors name the illegal digit plus the alphabet for the active base.
6. From “base” to “bytes”: endianness is a separate decision
Base conversion yields a mathematical integer, not a memory layout. The same 0x1234 is 12 34 big-endian and 34 12 little-endian — mixing protocol/file formats (usually big-endian on the wire) with x86 memory (little-endian) produces “value looks right, bytes are reversed”. When you need a byte view, fix a width (16/32/64) first, then split by endianness; this tool does not reorder endianness, so math conversion and serialization stay separate steps.
7. Permissions, masks, and colors: three frequent decimal↔hex jobs
- Unix mode 0755 is octal three-digit thinking — convert from octal, do not treat 755 as decimal first.
- Netmask /24 → 255.255.255.0: compute host bits, then hex when matching packet headers.
- CSS #RRGGBB is two hex digits per channel; batch-convert lists after stripping #.
- Snowflake IDs often print decimal in logs and hex in debuggers — round-trip on the same BigInt path to avoid Number precision loss.
FAQ
Neither. Every conversion is computed digit-by-digit with BigInt inside your browser, and the numbers you enter never leave your device.
Presets cover binary, octal, decimal, and hexadecimal; you can also set any custom radix from 2–36 as input (e.g., Base36 short codes) and optionally emit one extra output base. Batch mode (one value per line) and letter-case toggling are included.
No. Parsing and formatting go through BigInt digit-by-digit, so 64-bit hex values, snowflake IDs, and anything past JavaScript's safe-integer range round-trip losslessly.
Prefixes are recognized when they match the selected source base. Decorated literals like #FF5733 or AA:BB:CC need the # and colons stripped first — the tool converts bare digit strings. And beware the classic debugging mistake: reading a hex log value as decimal, or the other way around.
No — integers only. A decimal point or a space inside a number triggers an error that points at the offending digit. How floats map to binary is an IEEE 754 encoding question, a different problem from base conversion; use a dedicated floating-point bit-pattern tool for that.
No. Base conversion gives the mathematical value of the integer; the tool does not reorder bytes. The same 0x1234 is written 12 34 big-endian and 34 12 little-endian. When network byte order (almost always big-endian) meets x86 little-endian memory, fix the width (16/32/64) first and split bytes by endianness, or the value will be right while the bytes come out reversed.
Related Tools
Related Articles
Online Number Base Converter: Bases 2–36 and Large Integers
Use an online number base converter for binary, octal, decimal, hex, and any radix 2–36. Covers BigInt-safe large integers, batch conversion, letter case, and common pitfalls.
Online Base64 to Image Converter: Decode Base64 Strings to Image Files
Learn how to convert Base64 encoded strings back to image files. Understand Base64 decoding principles, common image MIME types, and real-world Web development use cases.
Online Image to Base64 Converter: Encode Images to Text Strings
Learn how to convert image files to Base64 encoded strings. Understand Base64 encoding principles, use cases, and how to inline images in frontend development.