Text Size for Distance Calculator
Minimum legible font/letter height for a viewing distance — for signage, slides and accessibility.
Letters subtend an angle at the eye — the same physics as the optician's chart. Rule of thumb: ~1 cm of letter height per 3 metres for comfortable reading, more for signage glanced at speed. For presentations, this is why '30pt minimum' fails in a big room: a back-row viewer at 15 m needs ~65 mm caps, roughly 36–40pt on a projected slide depending on screen size.
Formula
For general information only — not medical advice, a diagnosis or a treatment plan. Consult a qualified healthcare professional before making health, diet, medication or exercise decisions.
Minimum legible font/letter height for a viewing distance — for signage, slides and accessibility. The Text Size for Distance Calculator is a free, private text size for distance tool — every result computes instantly in your browser with no sign-up and no data upload.
About Text Size for Distance Calculator
Letters subtend an angle at the eye — the same physics as the optician's chart. It applies letter height = distance × tan(angle); legibility ≈ 5 arcmin minimum. Use the Text Size for Distance Calculator to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Text Size for Distance Calculator
- 1Enter your details in the Text Size for Distance Calculator input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Text Size for Distance Calculator?
- ✓Instant text size for distance result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (ISO 28564 / signage legibility standards; visual-acuity geometry)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Text Size for Distance Calculator work?+
Letters subtend an angle at the eye — the same physics as the optician's chart. The calculation uses the formula: letter height = distance × tan(angle); legibility ≈ 5 arcmin minimum. Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Text Size for Distance Calculator accurate, and what is it based on?+
The method is traceable to authoritative sources: ISO 28564 / signage legibility standards; visual-acuity geometry. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Text Size for Distance Calculator free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is for general information only and is not medical advice. Always consult a qualified healthcare professional before making health decisions.
What can I use the Text Size for Distance Calculator for?+
It's commonly used for text size for distance, font size signage, readable letter height. Minimum legible font/letter height for a viewing distance — for signage, slides and accessibility.
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