Method. Required lumens per room = (FC target × Area) ÷ (CU × LLF). CU (coefficient of utilization) is derived from the Room Cavity Ratio — a function of ceiling height and room size — with the ceiling and wall reflectances (white surfaces bounce more light, so fewer lumens are needed). Baseline shows the simpler Area × FC figure that reconciles with the studio schedule. The daylight credit is a nominal daytime offset (glazing × credit × orientation), capped at 50% so night lighting stays adequate. Foot-candle targets follow the IES / Energy Trust residential & commercial guides and are editable per room. A design aid — verify against a photometric layout for critical spaces.