Billiards players are reflection physicists — angle in equals angle out, on every bank shot. But geometry is only half the story; the other half is how much light actually bounces. The reflected intensity equals the incoming intensity times the surface's reflectance, I_reflected = I₀ × R, where R runs from 0 (a black hole of a surface) to 1 (a perfect mirror). Fresh snow reflects about 0.9 of sunlight, which is why skiers sunburn under their chins; asphalt manages only about 0.1, which is why parking lots bake.

This calculator runs the intensity multiplication. Type the incoming light intensity into Variable A — lux, watts per square meter, or any consistent unit — and the surface's reflectance as a decimal into Variable B; the Result box gives the reflected intensity. An architect in Phoenix comparing window glass, for instance, enters the desert sun's 100,000 lux in Variable A and 0.08 for low-E glass in Variable B, reading 8,000 lux of glare off the facade. Photographers balancing bounce cards, highway engineers rating road paint, and greenhouse designers all multiply through this same equation.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Reflection Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.