QR Code Capacity Calculator
Why the Same QR Code Can't Hold Unlimited Text
A QR code's capacity is fixed by two choices made at generation time: its version (which sets the grid size, from a compact 21x21 modules at version 1 up to a dense 177x177 at version 40) and its error correction level (which trades away usable data capacity in exchange for the code staying readable even if part of it is damaged or obscured). Pack too much text into too low a version and the encoder either fails outright or is forced to a higher version that produces a denser, harder-to-scan code.
The Reference Data
For versions 1 through 10, this calculator reads capacity directly from the official QR Code (ISO/IEC 18004) specification's alphanumeric-mode capacity table — these figures are exact, not estimated. Versions above 10 are not in the hardcoded exact table; for those the calculator extrapolates from the version-10 figure by scaling with the module grid area:
Capacity(v) ≈ Capacity(10) × [Side(v)² ÷ Side(10)²]
This extrapolation is flagged explicitly as approximate in the calculator's output, since it isn't pulled from the official table for those higher versions.
Where This Matters
- Choosing a QR version before generating — checking that a URL, Wi-Fi credential string, or contact card will actually fit at a target version before running it through a generator.
- Error correction tradeoffs — a code printed small or expected to get scuffed benefits from a higher error correction level, but that level eats into usable capacity, so this calculator quantifies exactly how much.
- Print size and scan reliability — higher versions pack more modules into the same physical size, making each module smaller and the code more sensitive to print quality and camera focus at a given size.
- Choosing the right encoding mode — capacity in numeric-only mode is meaningfully higher than alphanumeric, and byte mode is lower, so knowing the alphanumeric baseline helps judge whether a different mode is worth targeting.
Exact Alphanumeric Capacity, Versions 1–10
| Version | Modules | L (~7%) | M (~15%) | Q (~25%) | H (~30%) |
|---|---|---|---|---|---|
| 1 | 21x21 | 25 | 20 | 16 | 10 |
| 2 | 25x25 | 47 | 38 | 29 | 20 |
| 5 | 37x37 | 154 | 122 | 87 | 65 |
| 10 | 57x57 | 395 | 311 | 221 | 167 |
These figures come directly from the ISO/IEC 18004 specification's alphanumeric capacity table. Higher error correction always reduces capacity at the same version, since more of the code's data is spent on redundancy rather than payload.
How to Use This Calculator
- Enter the QR Version, from 1 to 40.
- Select the Error Correction Level: L, M, Q, or H.
- Select Calculate to see the maximum alphanumeric character capacity for that combination, along with the module grid size.
Related Calculations
Working with raw file sizes instead of QR payloads? See the File Size Calculator, or convert binary data representations with the Binary Calculator.