Free Telescope Magnification Calculator
Calculate the magnification of a telescope from the focal lengths of the objective and eyepiece: M = f_obj / f_eye.
mm
mm
Magnification
48.0 ×
Magnification vs Objective Focal Length
Telescope Magnification
M = f_objective / f_eyepiece
Swapping eyepieces changes magnification. The maximum useful magnification is roughly 2× per mm of aperture (e.g., 300× for a 150 mm telescope).
Example Calculation
1200 mm scope with a 25 mm eyepiece.
- 01M = 1200 / 25 = 48×
- 02Objects appear 48 times larger (linearly).