Lens Thickness Calculator

The calculator below will estimate the lens thickness of your glasses, in millimeters. "Lens thickness" means the thickest part of the lens, which for people who are nearsighted (negative sphere power) is the edge, and for people who are farsighted (positive sphere power) is the center. It will also tell you what the thinnest part of the lens will measure - for nearsighted people, this is the center of the lens, and for farsighted people, this is the edge.

All you need is your prescription, your PD, the lens material and the size of the frame. Make sure when entering the numbers to include a minus sign (-) if it's a minus number. Note, the measurements are an estimate only and are generally within 0.3mm of the actual measurement. The calculator is less accurate for high power, high cylinder, large eye sizes and non-traditionally shaped frames, but is still generally within 1.0mm.

We've also put together some tips on reducing lens thickness you can check out after the calculator.

Tips on Reducing Lens Thickness

1. Choose a Higher Index Lens Material
   This is the best way to reduce lens thickness. The higher the index of a lens material, the thinner the lens will be. The lowest index material is CR-39, or plastic, with an index of 1.5. Crown Glass is slightly higher at 1.52, but is thick and much heavier than CR-39. Trivex is next, with an index of 1.53. It is slightly thinner and lighter. The next lowest is mid-index, with an index of 1.56. The next one up is polycarbonate, with an index of 1.59. This is a good choice because it is both thin and light, but not much more expensive than plastic. After polycarbonate come the "high index" materials. These are all plastic lenses with indexes of 1.6, 1.67, 1.7 and up to 1.74. 1.74 is the thinnest plastic lens available. To get higher than that you need to switch to glass, where lenses with indexes of 1.8 and 1.9 are available. There are only a few labs that are able to offer high-index glass lenses. Typically, the higher the index of the lens material, the more expensive it is.


2. Choose a Full Rim Plastic Frame
   This is a tip for those who are near sighted seeking to reduce edge thickness. While not actually reducing lens thickness, by choosing a plastic frame much of the thickness can be hidden. Compared to a thin metal frame or rimless style, a plastic frame can provide quite a bit of camouflage at the edges.


3. Opt for Polished Edges
   Applying a glossy polish the edges of the lens make it less noticeable as it will appear clear when viewed from the side. If you have a particularly strong prescription though, you'll likely want to go for satin polish over glossy, because the latter can increase internal reflections (reflections in the lens that occur from light entering the side). Although satin polish is a little more noticeable than glossy, it is worth it for high prescriptions.


4. Edge Tinting
   Another option is to tint the edges of the lens in a color that matches the frame. This is a good option for lenses placed into plastic frames, where a dark color can be applied to the edges that stick out so they appear to be part of the frame. A tint matching the color of your skin can also be applied.


5. Rolling the Edges
   This tactic used to be favored more in the past before polycarbonate was widely available. Rolling the edges involves rounding the edges of the lens to create a curved edge that makes the lenses appear slightly smaller. This is typically the last option to try when trying to reduce edge thickness, as it's not the most cosmetically appealing.

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