Signage Letter Height Calculator

Work out signage letter height instantly with clear inputs, formula shown and shareable results.

About Signage Letter Height Calculator

Signage legibility follows a fixed ratio of viewing distance to cap height, commonly one millimetre of letter height for every 250 millimetres of distance. The ratio derives from the eye's angular resolution, which is why the same rule works for a shop fascia and a motorway gantry at very different scales.

Formula

Letter height

cap height mm = viewing distance mm / legibility ratio

Worked example

With the default values below, Signage Letter Height Calculator returns Cap height required of 60.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Maximum viewing distanceminimum 0.1 m: 15 m
Legibility standardone of Comfortable reading (1 mm per 200 mm of distance), Standard signage (1 mm per 250 mm), Minimum legible (1 mm per 400 mm): Standard signage (1 mm per 250 mm)

Results

Cap height required: 60.0 mm
Cap height in inches: 2.362 in
Equivalent cap height in points: 170.1 pt
Distance per millimetre of height: 250

Step by step

1Values used
2Letter height
3Cap height required= 60.0 mm
4Cap height in inches= 2.362 in
5Equivalent cap height in points= 170.1 pt
6Distance per millimetre of height= 250

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 the Signage Letter Height figure worked out?

cap height mm = viewing distance mm / legibility ratio. Signage legibility follows a fixed ratio of viewing distance to cap height, commonly one millimetre of letter height for every 250 millimetres of distance.

Why does this matter?

The ratio derives from the eye's angular resolution, which is why the same rule works for a shop fascia and a motorway gantry at very different scales.

What do I need to enter?

Enter maximum viewing distance, legibility standard. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.