Laser Focusability (Gaussian Beam)

For a collimated beam, the diffraction-limited focal spot size of a laser beam depends on its wavelength, the size of the beam at the lens and its M2 value. Use this simple calculator to determine your laser's diffraction-limited focal spot size, assuming an ideal lens without aberrations and a collimated laser beam. If the beam is not collimated, then the full Focal Spot Size Calculator should be used (set p to 0.01 and fill in λ, fl, θ, d).


Check our other laser measurement tools:

Sensor Finder  • Laser Peak Power Calculator  • Laser Focal Spot Size Calculator  • Laser Power Through Aperture Calculator  • Laser Focusability Calculator


Laser Focusability (Gaussian Beam)


(nm) *

Lens focal length

(mm) *

Beam diameter (at lens)

This is the 1/e2 diameter of the Gaussian beam. It's the point at which the power is about 13.5% of the peak power.

(mm) *



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