19Jan2033
Base64 encodes each set of three bytes into four bytes. In addition the output is padded to always be a multiple of four.
A rough approximation would be that the size of the data is increased to 4/3 of the original.
The max body size will typically be 1.34x larger than the file being uploaded. For example, the above limit 100M will only allow a 74M file to be uploaded.