Base64 Size Calculator
Calculate the size increase from Base64 encoding binary data.
About Base64 Size Calculator
Base64 turns every three bytes into four characters, a fixed 33 per cent increase before line breaks. That overhead is why inlining large images as data URIs makes pages heavier rather than lighter. The encoding exists to move binary safely through text channels, so the 33 per cent cost is a transport necessity rather than a compression choice.
Formula
Base64 Size
Encoded size = ⌈bytes ÷ 3⌉ × 4, plus one byte per wrapped line
- padding
- Output is always a multiple of four characters
- expansion
- Three input bytes become four output characters
Worked example
With the default values below, Base64 Size Calculator returns Base64 Encoded Size of 202,631. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Original sizeminimum 0 bytes
- 150,000 bytes
- Line wrap width, zero for noneminimum 0
- 76
Results
- Base64 Encoded Size
- 202,631 bytes
- Added Overhead
- 52,631 bytes
- Size Increase
- 35.087%
- Encoded Size
- 197.882 KB
- Line Break Overhead
- 2,631 bytes
Step by step
- 1Values used
- 2Base64 Size
- 3Base64 Encoded Size= 202,631 bytes
- 4Added Overhead= 52,631 bytes
- 5Size Increase= 35.087
- 6Encoded Size= 197.882 KB
- 7Line Break Overhead= 2,631 bytes
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Base64 Size calculated?
Encoded size = ⌈bytes ÷ 3⌉ × 4, plus one byte per wrapped line Base64 turns every three bytes into four characters, a fixed 33 per cent increase before line breaks. That overhead is why inlining large images as data URIs makes pages heavier rather than lighter.
Why does Base64 Size matter?
The encoding exists to move binary safely through text channels, so the 33 per cent cost is a transport necessity rather than a compression choice.
What values do I need to enter?
This calculator takes 2 inputs: Original size, Line wrap width, zero for none. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.