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Many people want to convert their eyeglass prescription to reading glasses. You can skip the calculation process mentioned in this article and contact your eye care professional directly; there is no problem with this. But, of course, if you want to understand the whole conversion process clearly, you can continue reading below. This is the primary purpose of our popularization of this process.

Before choosing your eyeglasses, we go through an optometric examination, at the end of which the eye care specialist will handwrite or print out a copy of your eyeglass prescription form. This contains all the data and information you need for your eyeglasses prescription. Of course, if you want to know what each piece of data means, you can refer to our How to Read Your Prescription.

The primary prescription (shown above) data that need to be used for the conversion process are sphere (SPH) and ADD, and you only need to know the addition of numbers. It's that simple! You don't even need to know what they mean. So how to convert eyeglass prescriptions to reading glasses? See the formula below.

The calculation for conversion of progressive eyeglass prescription to reading glasses:

Sphere (SPH) + ADD = New Sphere (Reading)

Is it straightforward? Of course, there are some notes.

  • The addition in the formula above must be summed with the sign.
  • The left and right eyes are calculated separately.
  • If astigmatism (CYL) and Axis data are available for left and right eyes, please keep them the same.

We provide some helpful examples here to illustrate this conversion process more clearly. For example, suppose your eyeglass prescription has a sphere (SPH) -1.75 and ADD 2.25. The new Sphere (SPH) based on the formula above is the original SPH (-1.75) plus the ADD (2.25), resulting in 0.50 (usually, the prescription is kept to two decimal places). This is the Sphere (SPH) data for reading glasses. If there is astigmatism (CYL) and Axis remains the same.

Another example is if you have a Sphere (SPH) that is 3.00 and ADD is 1.75, the same formula as above, using the original Sphere (SPH) (3.00) plus the ADD (1.75), results in 4.75. It is the Sphere (SPH) of your reading glasses. Again, if there is astigmatism (CYL) and Axis should be kept the same. Isn't it simple?

Finally, two sets of prescriptions are listed. One is the prescription for glasses before the conversion, and the other is the prescription for reading glasses after the conversion. You can try the calculation yourself.

Eyeglasses Prescription

Reading glasses after the conversion