Telescope Magnification Calculator

Find a telescope's magnification from its focal lengths.

Objective focal length

Eyepiece focal length

Magnification (×) 40

Formula: M = f_objective ÷ f_eyepiece

Step-by-step with your numbers:

1. Values used:

2. Objective focal length = 1,000

3. Eyepiece focal length = 25

5. Magnification = Objective focal length / Eyepiece focal length = 1,000 / 25 = 40×

Did we solve your problem today?

Telescope magnification is set by the ratio of objective to eyepiece focal lengths.

The math behind it

M = f_objective ÷ f_eyepiece. A shorter eyepiece gives higher magnification.

1000 mm objective with a 25 mm eyepiece → 40×.

Is more magnification always better?

No — useful magnification is limited by aperture and seeing conditions.