[tzot]

> When compared to encoding a value directly in binary, base64 has about a 25% overhead (6 bits /8 bits, 3/4).

The original data take ≥25% less space than the base64-encoded data, but the base64-encoded data take ≥33⅓% more space than the original data. The overhead is about 33⅓%.

[Zamicol]

That's correct.