Reading glasses strength estimator

About this calculator

Focusing power for close work declines with age. This estimator uses your age and usual reading distance to suggest a store reading glasses strength to try first.

What you need

• Your age
• Your usual reading distance: book or phone, close work, tablet or computer screen
• Confirmation that you see clearly far away without glasses and have no known eye condition

How it is calculated

Minimum amplitude of accommodation (Hofstetter) = 15 − 0.25 × age, in diopters. Focusing needed = 100 ÷ reading distance in cm. Suggested reading add = focusing needed − half the amplitude, rounded up to the next 0.25 D and capped at +3.50 D.

What the result can and cannot tell you

This is an estimate to try in a store, not a prescription. Store readers have the same power in both lenses. An eye exam also checks for conditions such as glaucoma and cataract that cause no symptoms early. See an eye doctor soon if you notice sudden blurring, distortion, double vision, flashes or new floaters.

References

1. Amplitude of accommodation (Hofstetter formulas)
2. Netra Eye Institute: Presbyopia

Related

• Visual acuity converter
• Glasses prescription reader
• Glasses to contact lens converter
• Presbyopia 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.