Enter the least distance of distinct vision and the focal length into the Calculator. The calculator will evaluate the Magnifying Power. 

Magnifying Power Formula

MP = 1 + D/F


  • MP is the Magnifying Power (())
  • D (mm) is the least distance of distinct vision
  • F (mm) is the focal length

To calculate Magnifying Power, divide the least distance of distance vision by the focal length, then add 1 to the result.

How to Calculate Magnifying Power?

The following steps outline how to calculate the Magnifying Power.

  1. First, determine the least distance of distinct vision. 
  2. Next, determine the focal length. 
  3. Next, gather the formula from above = MP = 1 + D/F.
  4. Finally, calculate the Magnifying Power.
  5. 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.

least distance of distinct vision = 85

focal length = 734

Frequently Asked Questions

What is the least distance of distinct vision?

The least distance of distinct vision, often referred to as the near point, is the closest distance at which the eye can focus on an object. It is typically about 25 cm for a healthy adult eye.

How does focal length affect magnifying power?

The focal length of a lens influences the magnifying power, with shorter focal lengths providing greater magnification. This is because magnifying power increases as the focal length decreases, according to the formula MP = 1 + D/F.

Can magnifying power be negative?

No, magnifying power cannot be negative because it represents the ratio of the size of the image to the size of the object, which is always a positive value. Negative values in optics typically indicate inverted images, not magnification.

Why is adding 1 necessary in the magnifying power formula?

Adding 1 in the magnifying power formula (MP = 1 + D/F) accounts for the distance the image is projected beyond the focal point. This adjustment is essential for accurately calculating the overall magnification effect of the lens on the viewed object.