Decoded Size Estimator

The Decoded Size Estimator works out the original byte size of data from a Base64 string or its character length, accounting for padding. It is for developers checking how big encoded data will be once decoded.

Knowing the decoded size helps you anticipate storage and limits before decoding. Estimating it locally is instant and keeps the data private.

1. Paste a Base64 string, or enter its character length.
2. The estimator calculates the original decoded size.
3. Review the figure, with padding taken into account.
4. Use it to plan handling of the decoded data.

• Decoded-size estimation
• Works from a string or a length
• Padding-aware calculation
• Runs in the browser — Decoded Size Estimator

• Estimating how large a file will be after decoding
• Checking decoded size against a storage limit
• Planning memory use before decoding a large payload
• Verifying an encoded value matches an expected size

• Remove whitespace from the string before estimating from its length.
• Account for padding, which affects the decoded byte total.
• Use the estimate to check decoded data against limits before processing.

• Ignoring padding, which changes the decoded byte count.
• Estimating from a string that includes whitespace, which skews the length.
• Assuming decoded size equals encoded size, when it is about a quarter smaller.