Font Size For Distance Calculator

Work out font size for distance instantly with clear inputs, formula shown and shareable results.

About Font Size For Distance Calculator

Character height is set by the angle it subtends at the eye: height equals twice the distance times the tangent of half the target angle in arc minutes. Around 20 arc minutes is comfortable for sustained reading, which is why 16 px body text at arm's length and a 40 mm slide heading at the back of a room are equivalent.

Formulas

Physical height

height = 2 x distance x tan(arc minutes / 60 / 2 in degrees)

Point size

points = height in mm x 2.8346

Worked example

With the default values below, Font Size For Distance Calculator returns Cap height in points of 32.98. Change any input above and every figure here is recalculated in your browser.

Inputs used

Reading distanceminimum 0.05 m: 2 m
Target character height in arc minutesaccepts 1–120: 20
Screen pixel densityminimum 1 ppi: 96 ppi

Results

Cap height in points: 32.98 pt
Cap height in millimetres: 11.636 mm
Cap height in device pixels: 43.98 px
Cap height in CSS pixels: 43.98 px

Step by step

1Values used
2Physical height
3Point size
4Cap height in points= 32.98 pt
5Cap height in millimetres= 11.636 mm
6Cap height in device pixels= 43.98 px
7Cap height in CSS pixels= 43.98 px

Assumptions and limits

The result is derived only from the 3 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 Font Size For Distance figure worked out?

height = 2 x distance x tan(arc minutes / 60 / 2 in degrees). Character height is set by the angle it subtends at the eye: height equals twice the distance times the tangent of half the target angle in arc minutes.

Why does this matter?

Around 20 arc minutes is comfortable for sustained reading, which is why 16 px body text at arm's length and a 40 mm slide heading at the back of a room are equivalent.

What do I need to enter?

Enter reading distance, target character height in arc minutes, screen pixel density. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.