Base64 Size Calculator

About this calculator

This calculator finds the encoded output size when data is converted to Base64, using ceil(n/3)×4 bytes for n input bytes, since Base64 encoding groups every 3 raw bytes (24 bits) into 4 encoded characters (6 bits each, from a 64-character alphabet) — padding with = characters when the input isn't a multiple of 3. This structure explains why Base64 output is always roughly 33% larger than the original binary data.

Web developers embedding images or files as data URIs, API developers estimating payload size when binary data (like file uploads or authentication tokens) must travel through JSON or XML, and backend engineers sizing database columns or message queue limits for encoded content use this. Enter the original data size to get the encoded size and overhead.