SpecFitMinimum lens height for progressive lenses
Progressive lenses need a minimum amount of vertical space to work. Go below it and the lens has nowhere to put your reading zone. This is the number to check before you choose a small frame.
Two numbers, not one
As covered in our guide to frames for progressive lenses, two measurements decide whether a frame works, and it pays to know which one you are looking at.
Lens height, sometimes called the B measurement, is the full vertical size of the lens: top edge to bottom edge. It is a property of the frame alone.
Fitting height is measured from the centre of your pupil down to the bottom edge of the lens, with the frame sitting on your face. It depends on the frame and on where your eyes land in it, which is why the same frame suits one person and not another.
Working minimums
Treat the table below as a starting point, not a guarantee. Every progressive design has its own published minimum fitting height, and your optician knows exactly which lens they are ordering for you. Ask for the number before you buy a frame.
| Design | Minimum lens height | Minimum fitting height | Trade-off |
|---|---|---|---|
| Standard corridor | 28 - 30 mm | 17 - 18 mm | Wider intermediate zone, needs a deeper frame |
| Short corridor | 22 mm or more | 13 - 14 mm | Fits smaller frames, narrower intermediate zone and more peripheral blur |
A short-corridor design suits people who mostly need distance and reading, and use the intermediate range less. If you spend long hours at a screen, ask your optician whether a short corridor still serves you before you choose one for the sake of a smaller frame.
Why the minimum exists
A progressive lens stacks three zones into one piece of glass: distance at the top, intermediate in the middle, and reading at the bottom. The corridor between distance and reading has a fixed length by design, set by the lens maker, not by the frame you choose. Cut the lens too short and the reading zone is trimmed off the bottom or squeezed into a sliver too small to use comfortably.
Checking a frame before you buy
- Look for "lens height" or "B" in the product listing. If a size stamp carries a fourth number, that is usually it, as in 54□17 140 32. See our guide to the size stamp for the other three.
- If lens height is not listed, ask the retailer directly. Estimating it from a photo is a last resort, and an unreliable one.
- Compare the number against the minimum your optician gave you for the specific lens you are ordering.
- Remember that fitting height, not just lens height, is what finally decides whether the reading zone fits, so confirm both.
Shapes that give you height
Rounds, squares with deep lenses, aviators, and browlines with a deep lower rim all give a progressive lens the room it needs. Slim rectangles, narrow ovals, and shallow browlines fight you, since their lens height often sits below even a short-corridor minimum. Our guide to frames for progressive lenses covers the full set of shapes and the ones to avoid.
Bigger is not always better
A tall lens is not automatically a better one. A very tall lens adds weight and thickness, which matters more with a strong prescription, and it leaves a large area at the bottom that sits below your reading zone and stays blurred. For most people, 30 to 36 mm of lens height is a comfortable band: enough for the corridor and both usable zones, without carrying glass you never look through.
Fit matters more than usual
The zones in a progressive lens are positioned relative to your pupil, so the frame has to sit at the height it was fitted at. A frame that slides down your nose carries the reading zone down with it, and your eyes end up looking through the wrong part of the lens. Check the fit with the 10-point checklist, and pay particular attention to how high the frame sits on your nose.
SpecFit reads a frame's size stamp and checks the fit against your measured face. Paste a link to any glasses to check it, free. Rendering the frame on your own photo costs one credit.
Questions
What is the minimum lens height for progressive lenses?
About 28 to 30 mm for a standard progressive design, and about 22 mm or more for a short-corridor design, as a working rule. Confirm the exact figure with your optician for the specific lens you are ordering.
What is the minimum frame size for progressive lenses?
There is no single minimum frame size. Lens height is what decides it, not the frame's overall width or shape, so a narrow frame with a deep lens can still work.
What is the smallest frame I can use for progressives?
The smallest one that still clears your lens's minimum fitting height, usually 13 to 14 mm for a short-corridor design. Nothing smaller will hold the reading zone, whatever the frame looks like.
Is a taller lens always better for progressives?
No. A very tall lens adds weight and thickness, especially with a strong prescription, and leaves a large blurred area at the bottom that you never look through. About 30 to 36 mm is a comfortable band for most people.