Base64 Size Calculator
See exactly how much bigger your data gets after Base64 encoding. Curious why? Read why Base64 makes files ~33% larger.
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Base64 Size Calculator — FAQ
Why does Base64 make data bigger?+
Base64 represents every 3 bytes of input as 4 output characters, so the encoded size is always about 4/3 (roughly 33%) larger than the original.
What is the exact formula for Base64 output size?+
ceil(inputBytes / 3) * 4. For example, 10 bytes becomes ceil(10/3)*4 = 4*4 = 16 characters.
Does the 33% overhead apply to all variants?+
Standard and URL-safe Base64 have the same core overhead. URL-safe Base64 without padding is very slightly smaller since it drops the trailing "=" characters.
Should I worry about Base64 overhead for large files?+
For large binary files (images, videos, attachments), the extra ~33% can matter for bandwidth and storage — consider whether you actually need text-safe encoding or can transmit raw bytes instead.