Label Reading Distance Character Height Rule Checker

Actual label angular height2atan(h/2d) under caller independently applicable readability screen. Typography, contrast, language, vision, placement and access remain unresolved; not guarantee legibility.

Description

Character angular height relates measured letter height to reading distance.

Character angular height relates measured letter height to reading distance.^[1]

A supplied minimum angle is a screening assumption rather than a complete readability assessment.

When to use Label Reading Distance Character Height Rule Checker

Use this tool to calculate or review the supplied observations under the stated rules. Establish the object or visitor scope, measurement units and independently applicable conservation, engineering, access or editorial reference.

How to use Label Reading Distance Character Height Rule Checker and understand its results

Establish the object or visitor scope, measurement units and independently applicable conservation, engineering, access or editorial reference.
Enter observedLabelCharacterHeightMm, observedReadingDistanceMm, callerRequiredCharacterAngularHeightDegrees, using the field meanings and rules below, then run the tool.
Read result.observedCharacterAngularHeightDegrees, result.meetsCallerAngleScreen. Use the units and sign conventions below.
Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.

Input field	Meaning	Value type	Requirement
observedLabelCharacterHeightMm	Observed label character height mm	number	Required
observedReadingDistanceMm	Observed reading distance mm	number	Required
callerRequiredCharacterAngularHeightDegrees	Caller required character angular height degrees	number	Required

Require nonnegative character height, positive reading distance in matching millimeters and positive supplied minimum angular height in degrees. Compute the full angle 2×atan(height/(2×distance)) in degrees and compare inclusively with the minimum. No font, contrast or audience assessment occurs.

angularHeightDegrees=(360/pi)×atan(characterHeightMm/(2×distanceMm)); meets=(angle≥requiredAngleDegrees)

Use the matching field units and the exact boundary, ordering and reference rules above.

Output field	Meaning	Value type
result	Structured result; its nested fields below contain the actual calculation or selected reference	object
result.observedCharacterAngularHeightDegrees	Observed Character Angular Height Degrees	number
result.meetsCallerAngleScreen	Meets Caller Angle Screen	boolean

json

{
  "input": {
    "observedLabelCharacterHeightMm": 10,
    "observedReadingDistanceMm": 1000,
    "callerRequiredCharacterAngularHeightDegrees": 0.5
  },
  "output": {
    "result": {
      "observedCharacterAngularHeightDegrees": 0.572953020554149,
      "meetsCallerAngleScreen": true
    }
  }
}

Limitations and assumptions

Object condition, observation coverage and applicable references determine applicability. A supplied comparison or record does not certify conservation treatment, engineering, access compliance or insurance eligibility.

Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Extremely large composite outputs are rejected.

Alternative or Complementary methods

For a related step, use Wheelchair Reach Display Height Compliance Checker: Wheelchair reach depends on the applicable access standard and the actual approach geometry. For a complementary comparison, use Object Viewing Distance Minimum Rule by Width Checker: Viewing-distance ratios compare an object width with a measured viewing distance.

References

Label Reading Distance Character Height Rule Checker — tool.io

Similar or alternative tools

Wheelchair Reach Display Height Compliance Checker
Wheelchair reach depends on the applicable access standard and the actual approach geometry.
Object Viewing Distance Minimum Rule by Width Checker
Viewing-distance ratios compare an object width with a measured viewing distance.