Magnification Calculator
This calculator gives the total magnification of a microscope or a telescope. For a microscope it multiplies the objective power by the eyepiece power, and for a telescope it divides the objective focal length by the eyepiece focal length. Switch instruments with one tap and read the combined magnification instantly.
How to find total magnification
- Choose your instrument by tapping the microscope or telescope button at the top.
- For a microscope, enter the Objective (x) power, such as 40, and the Eyepiece (x) power, such as 10.
- For a telescope, enter the Objective focal length and the Eyepiece focal length in the same unit, such as millimeters.
- Read the total magnification on the highlighted card, shown as a value followed by an x.
- Press Copy to save the result, for example Magnification = 400x.
Examples
Microscope objective times eyepiece
Objective = 40x, Eyepiece = 10x
Total magnification = 400x
Telescope focal length ratio
Objective focal = 1000 mm, Eyepiece focal = 25 mm
Magnification = 40x
High-power microscope
Objective = 100x, Eyepiece = 10x
Total magnification = 1000x
Frequently asked questions
How do you calculate microscope magnification?
Multiply the objective lens power by the eyepiece power. A 40x objective paired with a 10x eyepiece gives 400x total, and a 100x oil-immersion objective with the same eyepiece gives 1000x. The tool does this multiplication for you in the microscope mode.
How do you calculate telescope magnification?
Divide the focal length of the objective, meaning the main lens or mirror, by the focal length of the eyepiece. A 1000 mm objective with a 25 mm eyepiece yields 40x. Swapping in a shorter eyepiece raises the magnification.
Do the telescope focal lengths need the same units?
Yes. Magnification is a pure ratio, so both focal lengths must share a unit such as millimeters or inches. When the units match they cancel out and the result is a unitless number of times.
What does the x after the number mean?
The x is read as times and marks how many times larger the image appears in linear size. A 400x reading means details look 400 times bigger across than they would to the unaided eye at the same viewing distance.
Why must every value be greater than zero?
Lens powers and focal lengths are physical sizes that are always positive, so the calculator rejects zero or negative entries. If you leave a field blank or type an invalid value it shows a short prompt instead of a result.
Is more magnification always better?
No. Beyond a point extra magnification just enlarges a blurry image without revealing new detail, a limit set by the objective aperture and by diffraction. In telescopes a practical ceiling is roughly the aperture in millimeters times two, and pushing past it gives a dim, fuzzy view.
Does this account for a Barlow lens or tube length?
No. The tool uses the plain textbook formulas and does not include a Barlow multiplier, focal reducer, or nonstandard tube length. If you use a 2x Barlow, double the telescope result yourself.
What is the difference from angular or lens magnification?
This calculator gives the overall instrument magnification. A single lens or mirror uses image distance over object distance instead, and angular tools compare apparent sizes. See the related thin lens and lens magnification calculators for those cases.
Is anything I enter uploaded?
No. The math runs entirely in your browser and nothing is sent to a server, so the powers and focal lengths you try stay on your device.
Learn more
- Microscope vs telescope magnification
Why microscopes multiply powers while telescopes divide focal lengths, how to read the numbers on your gear, and when high magnification stops helping.
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