Laser Beam Spot Size Calculator

Your details

Laser wavelength. Common values: 532 nm (green), 1064 nm (Nd:YAG near-IR), 10600 nm (CO2 in nm = 10.6 um).
The 1/e² full beam diameter where it enters the focusing lens. Larger beams produce tighter focus.
Effective focal length of the focusing lens or objective. Shorter focal length gives a smaller spot but reduced depth of field.
M-squared (M2) is the beam quality factor: 1.0 is a perfect Gaussian (TEM00) beam. Real-world beams are typically 1.0 to 3.0 for single-mode fiber lasers, up to 10 or more for multimode or pulsed lasers.
Axial distance from the focal plane. Set to 0 to skip. Enter a value to find the beam radius at that position along the propagation axis.
Focused spot diameter (2w₀)Tight focus (5-50 um)
13.547

Full 1/e² beam diameter at the focal plane

Focused spot radius (w₀)6.774
Rayleigh range (zᴿ)135.473
Depth of field (2zᴿ)270.945
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Spot radius (w0)6.774
Rayleigh range (zR)135.473
Depth of field270.945

Focused spot diameter: 13.547 um

  • The focused spot diameter is 13.547 um, giving a spot radius (w0) of 6.774 um.
  • The depth of field is 270.945 um, meaning the beam stays within twice its minimum cross-sectional area across that axial range.
  • The Rayleigh range is 135.473 um: beyond this distance from the focus, the beam radius grows by a factor of sqrt(2) (about 41%).

Next stepYour beam is near-perfect Gaussian (M² = 1.00). To further reduce the spot size, increase the beam diameter at the lens or decrease the focal length.

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