Abstract: A laser system computer in the preferred form of a hand-holdable, two-sided circular slide rule, for quickly and accurately solving a wide range of problems which are associated with laser radar, designation, communications and directed energy applications, the solution of which said problems could not be attained with prior art slide rules of any type. Calculations relating to the design, analysis and performance of lasers are performed on one side of the calculator. Atmospheric effects, such as attenuation and turbulence beam spreading, are computed on the other side of the calculator. Both continuous wave and pulsed lasers can be calculated with the use of this unique computer, which also may be used for ground, air and space laser applications. Structurally, the preferred embodiment is in the form of a circular slide rule having: a circular stator (i.e., base) with a front face and a rear face; a plurality of concentric discs (i.e.