Eyewear and Vision
Reading glasses strength.
Enter your age and how far you hold what you read, and see a starting strength in diopters, with an age chart. It is an estimate from published average focusing-power formulas, so use it as a shopping starting point and get an eye exam. Runs in your browser; nothing is sent or stored.
Age and reading distance
Estimated reading add
Fill the form and press Calculate.
The short answer
At a 40 cm reading distance, this method gives about +0.75 at age 45, +1.25 at age 50, +2.00 at age 55 and +2.50 at age 60 and over. Treat it as a starting point; an eye exam gives the real number.
Worked example
Age 50, reading at 40 cm. Reading demand = 100 / 40 = 2.50 D. Hofstetter's minimum amplitude of accommodation = 15 - 0.25 x 50 = 2.50 D; the expected amplitude is 18.5 - 0.3 x 50 = 3.50 D. Using half the minimum amplitude leaves 1.25 D, so the add is 2.50 - 1.25 = 1.25, rounded up to a quarter step: +1.25.
At 55 and a 50 cm reading distance the demand is 2.00 D, the minimum amplitude is 1.25 D and the add is +1.50.
How it works
Near demand (D) = 100 / reading distance in cm. The eye's focusing reserve falls with age. Hofstetter's formulas give the amplitude of accommodation in dioptres: expected = 18.5 - 0.3 x age; maximum = 25 - 0.4 x age; minimum = 15 - 0.25 x age (not below zero). This tool uses the minimum, keeps a share of it in reserve (default one half), and sets add = demand - share x minimum amplitude, rounded up to the next 0.25 D and never above the demand itself.
If you already wear a distance prescription, the near value is added to it (EyeWiki), so a plain reading add is for people who see well far away without correction. People who are nearsighted, farsighted or have astigmatism, or whose two eyes differ, need an exam, not an over-the-counter pair.
Assumptions. The one-half reserve and the choice of the minimum amplitude are rules of thumb, not a published standard, and averages hide a lot of person-to-person spread. Over-the-counter readers are only suitable if both eyes see similarly and an eye exam has found no other problem.
Reading add by age (40 cm)
| Age | Minimum amplitude | Estimated add |
|---|---|---|
| 40 | 5.00 D | +0.00 D |
| 45 | 3.75 D | +0.75 D |
| 50 | 2.50 D | +1.25 D |
| 55 | 1.25 D | +2.00 D |
| 60 | 0.00 D | +2.50 D |
| 65 | 0.00 D | +2.50 D |
| 70 | 0.00 D | +2.50 D |
Computed by the same code as the calculator, reading at 40 cm and keeping half the minimum amplitude in reserve. Individual needs vary.
Sources (opened 2026-10-08): Wikipedia, Presbyopia (Hofstetter's formulas); EyeWiki (American Academy of Ophthalmology), Presbyopia.
FAQ
What strength reading glasses do I need at 50?
At a 40 cm reading distance the method here gives about +1.25. That is an average-based starting point, and your own number may differ by half a diopter or more.
How does reading distance change the strength?
A nearer distance needs more plus power. The reading demand is 100 divided by the distance in centimetres, so 40 cm is 2.50 D and 50 cm is 2.00 D.
Where do the age numbers come from?
From Hofstetter's formulas for amplitude of accommodation (expected 18.5 - 0.3 x age, maximum 25 - 0.4 x age, minimum 15 - 0.25 x age). The reserve rule on top is a common rule of thumb, not a published standard.
Why is the result the same from 60 up?
By the minimum formula the focusing amplitude is zero at 60, so the whole reading demand has to come from the lens. At 40 cm that is +2.50.
Do I still need an eye exam?
Yes. Near-vision problems can be caused by other conditions, and the two eyes often need different strengths. An exam is the way to get a correct prescription.
Can I use this if I already wear glasses?
The near value is added on top of a distance prescription, so this number alone would not be right. Ask your optician for an add or a separate reading prescription.
Disclaimer
Not medical advice. This tool does simple arithmetic on numbers you type in. It does not replace an eye exam, a prescription or the advice of an optometrist or ophthalmologist, and it is not a way to order or change a prescription. Difficulty reading up close can have causes other than ageing. See an eye-care professional.