Reading print enlargement

About this calculator

Two calculations for reading with low vision: how much to enlarge print to reach a size you can read comfortably, and how a magnifier’s diopter rating translates into the “×” number on the packaging.

What you need

• For print: the current print size and the size you can read comfortably, in points
• For a magnifier: its power in diopters

How it is calculated

Enlargement factor = preferred size ÷ current size. Print setting = factor × 100%. Magnifier rating = diopters ÷ 4 (some makers use diopters ÷ 4 + 1).

What the result can and cannot tell you

Typeface, letter spacing, contrast, lighting and reading distance all change how easy print is to read, so try the setting and adjust. Magnifier makers rate “×” in different ways; the diopter number is the more reliable way to compare. Choosing an optical magnifier needs a low-vision assessment.

References

1. German Jordanian University: Manual in vision rehabilitation, relative size magnification
2. Netra Eye Institute: Functional vision assessment questionnaire

Related

• Visual acuity converter
• Glasses prescription reader
• Glasses to contact lens converter
• Functional vision guide
• All eye calculators

For information only. These tools explain numbers and do not replace an eye examination or your eye doctor’s advice. Values you enter stay in your browser.