Base64 to Decimal Converter: Byte Values 0–255

How to convert Base64 to decimal

1. Paste the Base64 into Input · Base64. Spaces, line breaks, URL-safe characters and missing padding are fine.
2. The byte values appear in Output · Decimal bytes.
3. Choose Separator under the output: Space, , , , or New line.
4. Copy output or Download the list. The Decimal bytes → Base64 toggle, or Decimal to Base64, reverses the conversion.

Examples

The last row shows a handy use: binary formats store IPv4 addresses as four bytes, and the decimal list is the familiar dotted form without the dots.

Byte values or one big number

This converter lists bytes. Reading the whole Base64 value as a single integer gives a different answer, and one that depends on byte order: the two bytes 1 0 are 256 when read as a big-endian number and 1 when read as little-endian. Which one is right depends on the format that produced the data, so the conversion belongs in code where you can state it:

import base64
data = base64.b64decode("AQA=")
list(data)                       # [1, 0]
int.from_bytes(data, "big")      # 256
int.from_bytes(data, "little")   # 1

The same applies to Base64 that holds a 32-bit counter, a timestamp or a large ID: the decimal list gives the bytes, and int.from_bytes or DataView in JavaScript gives the number.

Where decimal byte lists are used

• JSON. Some serializers write binary data as an array of numbers. Node’s JSON.stringify(Buffer.from("Hi!")) gives {"type":"Buffer","data":[72,105,33]}. With the , separator and brackets you get the same shape.
• Python and spreadsheets. list(b) in Python prints decimal values, and a column of numbers (New line separator) pastes straight into a spreadsheet.
• Microcontrollers and serial monitors. Arduino code and many serial tools show bytes as decimal. For a typed array declaration in C or another language, Base64 to Byte Array writes the full literal.

If you are going to read the bytes rather than paste them somewhere, hex is usually clearer because every byte is exactly two characters: try Base64 to Hex.

Base64 to decimal in code

import base64
list(base64.b64decode("SGkh/w=="))     # [72, 105, 33, 255]

Array.from(Buffer.from("SGkh/w==", "base64")).join(", ");   // '72, 105, 33, 255'

In a browser without Buffer, Array.from(atob(s), c => c.charCodeAt(0)) gives the same numbers. The Python and JavaScript pages cover decoding in more depth.

FAQ