Enter the refractive index of the lens material, as well as the radii of curvature of both surfaces, into the calculator to determine the lens thickness; this calculator can also evaluate any of the variables given the others are known.

## Lens Thickness Formula

The following formula is used to calculate the lens thickness:

T = (n - 1) * (R1 - R2) / 2

Variables:

- T is the lens thickness
- n is the refractive index of the lens material
- R1 is the radius of curvature of the first surface of the lens
- R2 is the radius of curvature of the second surface of the lens

To calculate the lens thickness, subtract the radius of curvature of the second surface from the radius of curvature of the first surface. Multiply the result by the refractive index of the lens material and divide by 2.

## What is a Lens Thickness?

Lens thickness refers to the measurement of a lens from its front surface to its back surface at the thickest point. This measurement is typically given in millimeters and can vary greatly depending on the type of lens and its prescription strength. For example, a high prescription lens will typically be thicker than a low prescription lens. The thickness of a lens can also be influenced by the type of material used to make the lens, with some materials allowing for thinner lenses than others.

## How to Calculate Lens Thickness?

The following steps outline how to calculate the Lens Thickness:

- First, determine the refractive index of the lens material.
- Next, determine the desired lens power.
- Next, gather the formula from above = Lens Thickness = (Lens Power * 1000) / (Refractive Index – 1).
- Finally, calculate the Lens Thickness.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

Refractive index of the lens material = 1.5

Desired lens power = -3.75