If you've ever picked up a pair of reading glasses and wondered what +1.00, +1.50 or +2.00 actually means, you're not alone.
Those numbers tell you the strength of the lenses - or how much magnification they provide for close-up vision.
The basic rule is simple:
The higher the number, the stronger the magnification.
So +2.00 reading glasses are stronger than +1.50 readers, and +3.00 readers are stronger again.
Here's how it works - and how to make sense of the other numbers you might find on your glasses.
0.50, +1.00, +1.50, +2.00, +2.50 and +3.00 refer to lens strength. The higher the positive number, the stronger the magnification. These numbers are different from frame measurements such as 50–20–145.
What Does +1.00, +1.50 or +2.00 Mean on Reading Glasses?
Reading-glasses strength is measured in dioptres.
You'll usually see strengths written with a plus sign:
- +0.50 - low magnification
- +1.00 - lower magnification
- +1.50 - moderate magnification
- +2.00 - stronger magnification
- +2.50 - stronger again
- +3.00 - one of the higher strengths commonly available in ready-made readers
The number isn't a measure of quality, lens thickness or frame size.
It simply tells you the magnifying power of the lens.
What Is a Dioptre?
A dioptre is the unit used to measure the optical power of a lens.
For reading glasses, a larger positive dioptre number means more magnification.
For example:
+0.50 < +1.00 < +1.50 < +2.00 < +2.50 < +3.00
As close-up vision changes with age, you may find that the strength you prefer changes too.
Reading-glasses strength isn't a quality scale - stronger isn't better.
The goal isn't to choose the strongest readers you can tolerate.
It's to choose a strength that makes close-up text clear and comfortable at your normal reading distance.
Find Your Reading Glasses Strength →
Why Do Reading Glasses Have Plus Numbers?
Reading glasses are designed to provide additional focusing power for close-up tasks.
That's why ready-made readers are labelled with positive numbers such as +1.00 or +2.00.
Changes in close-up focusing are common with age, which is why many people begin using reading glasses in their 40s and beyond.
This is commonly associated with presbyopia, the normal age-related change in the eye's ability to focus on nearby objects.
Does a Higher Number Mean Better Reading Glasses?
No.
Higher means stronger - not better.
If +1.50 gives you comfortable, clear vision, moving to +2.50 won't improve the quality of your glasses.
In fact, choosing more magnification than you need can make reading uncomfortable.
Your ideal strength is simply the one that works comfortably for your eyes and your usual reading distance.
Not sure which number is right for you? See our guide to choosing the right reading glasses strength for a simple way to compare strengths without relying on age alone.
How Do I Know Which Reading Glasses Number I Need?
The right number is the strength that gives you clear, comfortable close-up vision at your normal reading distance.
Age can provide a rough starting point, but it shouldn't be used as the only way to choose reading-glasses strength.
We've covered this in detail in our complete guide:
HOW TO CHOOSE THE RIGHT READING GLASSES STRENGTH WITHOUT GUESSING →
Are the Numbers the Same for Both Eyes?
Standard over-the-counter reading glasses generally have the same magnification in both lenses.
So if you buy +2.00 readers, both lenses will usually be +2.00.
That's one of the important differences between ready-made readers and prescription eyewear.
If your eyes require substantially different correction, or you have other vision requirements, standard readers may not be suitable. An optometrist can assess your individual vision.
What Do Numbers Like 50-20-145 Mean?
Here's where things can get confusing.
You might also find a sequence of numbers printed inside the arm of your glasses, such as:
50-20-145
These are not your reading strength.
They're frame measurements.
Typically, they refer to measurements such as:
Lens width – bridge width – temple length
and are usually given in millimetres.
So:
+2.00 = lens strength
while:
50-20-145 = frame measurements
Both sets of numbers can help you choose readers — but they tell you completely different things.
Want to understand frame width, lens width, bridge width and temple length? See our Reading Glasses Size Guide →
Do I Need a Different Number for Computer Work?
Possibly.
A computer screen generally sits further from your eyes than a book or phone.
Because working distance matters, the strength you find comfortable for close reading may not necessarily be the strength you prefer at your computer.
If you spend much of your day working at a screen, read our:
Reading Glasses for Computer Work →
Reading Strength Is Only Half the Story
Once you've worked out the number you need, you get to choose the fun part.
The frames.
Reading glasses don't need to look like a medical necessity.
Choose a frame that fits well and works with your personal style — whether that's understated, colourful, classic, oversized or somewhere in between.
At Ministry of Sight, our readers are available in a range of strengths and frame styles, from classic round and square shapes to bold acetate and geometric designs.
Frequently Asked Questions
What does +1.50 mean on reading glasses?
+1.50 indicates the magnifying power of the lenses. It is stronger than +1.00 but weaker than +2.00.
Is +2.00 stronger than +1.50?
Yes. The higher the positive number, the stronger the magnification.
Is +3.00 a strong reading-glasses strength?
+3.00 provides considerably more magnification than lower strengths such as +1.00 or +1.50. The right strength depends on what feels clear and comfortable at your normal reading distance.
What does 50-20-145 mean on glasses?
Those numbers generally refer to frame measurements rather than magnification — commonly lens width, bridge width and temple length.
Do both lenses in reading glasses have the same strength?
Standard ready-made reading glasses generally use the same magnification in both lenses.
Should I choose stronger reading glasses if I'm unsure?
Not necessarily. Stronger isn't better. Aim for the lowest strength that provides comfortable, clear vision at your normal reading distance.
Know Your Number. Then Find Your Frame.
Understanding reading-glasses numbers is actually quite simple:
+1.00, +1.50, +2.00 etc = lens strength.
Higher number = stronger magnification.
Numbers such as 50-20-145 = frame measurements, not strength.
Once you've found the magnification that works for you, all that's left is finding a pair you actually want to wear.
