How many lights
does this room need?
Fixture count, spacing and a to-scale ceiling plan for any room — computed with the lumen method rather than a rule of thumb. Free, no signup.
Common room sizes
Why "one light per 4 square feet" gets it wrong
Almost every lighting calculator online uses a fixed rule: so many watts or fixtures per square foot. It is quick, and it is fine for an ordinary 8-foot-ceiling bedroom. It falls apart everywhere else.
Two rooms with identical floor areas can need very different amounts of light. A tall room loses more of it before it reaches the floor. A long, narrow room bounces less light off its walls than a square one — that relationship is captured by the room index, and it moves the answer by 30% or more between a cramped hallway and a large open space. And a kitchen is lit to roughly double a living room regardless of size.
This site runs the actual lumen method for every combination and draws the resulting layout, because the useful answer was never the number on its own — it is where the fixtures go.