45-75 CPL Optimal Band Check
Screen observed CPL against an explicitly illustrative inclusive 45–75 band; not universal optimality.
Description
Check characters per line against an illustrative inclusive 45-to-75 band.
A 45-to-75-character measure is a particular line-length heuristic. This checker identifies membership in that fixed band instead of declaring an optimal line length for every reading context.
When to use this tool
Check characters per line against an illustrative inclusive 45-to-75 band. Use it when the input measurements and conventions below match the operation you need.
- Prepare observedCpl, respecting the measurement basis and boundaries below.
- Compare the worked example with your intended operation before reusing its result.
How to use the tool and how it works
- Enter every field in the input table using the stated units and exact supported selector spelling where applicable.
- Run the tool. Correct input errors before interpreting an output.
- Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.
The supplied characters-per-line value must be nonnegative. The returned flag is true from 45 through 75 inclusive.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| observedCpl | Observed cpl. | Finite number; zero or greater |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.withinIllustrativeBand | Within illustrative band flag under the exact conditions described above. |
{
"input": {
"observedCpl": 60
},
"output": {
"result": {
"withinIllustrativeBand": true
}
}
}Limitations and assumptions
- The band is illustrative, not a universal readability or accessibility standard. Font, script, medium, reader and layout are not assessed.
- Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
- Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.
Alternative or Complementary methods
Compare the metric calculation with the intended font and rendered text. Font shaping and layout inspection are more appropriate when the task depends on actual glyph positions or reading conditions. Compare the scope of the nearby tools below before substituting one.
References
Similar or alternative tools
- optimal measure characters per line
Characters per line depend on word advances and wrapping, not just nominal font size.
- Line Length mm From CPL and Em
Line length from actual mean glyph advance in em and CPL, not a fixed half-em font assumption.