Lumens Calculator: Room-by-Room Watts That Feel Right

Calculate lumens per room without glare: lux targets, panel counts and strip lengths for 9-ft flats with 4000K base.

Two 18W panels in 12x14 left corners dark — lumens right, placement wrong. In Ain Borja 900 sq ft we calculated per room + spaced 3.5 ft — same watts felt 2x brighter. Base layers in living room lighting, bedroom in bedroom lighting.

Formula: lux x sqm = lumens, then fix placement

Need: living 150 lux ambient + 300 task zones, bedroom 100 + 300 reading, kitchen 200 + 400 counter, bath 200 + 300 face, hall 150, desk 500. Lumens = lux x sqm (12x14=15.6 sqm x150=2,340lm ambient). Panels: 18W=1,700lm, spots 7W=650lm. Count = lumens/efficacy + 20% dust/age loss.

Example 12x14 living ambient: 2,340 +20%=2,800lm = 1x18W panel (1,700) + 2x7W spots (1,300) = 3,000lm perfect. Task extra: floor lamp 800lm + strip 1,200lm dining — switched separate, not always on or bill + glare.

Room table (9-ft ceiling, 4000K base, CRI80+)

Living 12x14: ambient 2,800lm (1 panel +2 spots), task 2,000lm (lamp + pendant dim). Bedroom 10x12: ambient 1,500lm (1x18W dim), reading 800lm (2x swing 5W), accent 600lm strip. Kitchen 8x10: ambient 1,500lm, task 2,400lm (2x1m 14W/m strips). Bath 4x7: ambient 600lm + face 800lm sides (not top). Hall 3x12: 1,200lm 3 spots 3.5 ft. Desk 42-inch: 800lm 8W asymmetric + bias 200lm.

Phone lux app verify night: hold counter/desk/face height — below target add task, not bigger ambient that glares.

Spacing beats watts

Spots every 3-4 ft center, 18 inch off walls; wash mirror/art 12 inch off. Single center tube 36W in 12x14 gives 300 lux center + 60 corners (tunnel). Split 18W + spots evens ±15%. Curtain wash spot doubles perceived width same watts. No downlight above TV (glare) — 18 inch off wall.

Dimmer MAD 70 on living + dining + bedroom accent — movie/guest/sleep modes same lumens installed. Smart tunable one bulb MAD 100 covers 80% circadian benefit without whole-house cost.

Shop calculator: lumens not watts

Ask lumens: 18W must be 1,600-1,800lm, 7W 600-700lm. Low-lumen cheap needs double count + still dull. Driver branded 12V DC + aluminium + diffuser, not bare 220V tape that flickers + shocks wiping oil. IP20 living/bed, IP65 kitchen-stove/bath Zone 2. Phone wave test — lines = reject.

Keep 1 panel +2 spots same batch spare — temperature shifts lots, single replacement mismatches. Bill + model photo for 2-yr driver warranty.

Cost and power

900 sq ft total installed ~180W LED = 6h/day x30 x MAD 1.2/kWh = MAD 39/month. Over-light 350W doubles bill + glare with zero benefit. Right lumens + placement saves MAD 400/year + headaches. Kit cost MAD 4,500-7,000 whole flat mid (panels, spots, strips, lamps, dimmers + 68 points labor).

Daylight harvest: sheer day curtain + light quartz + same-white ceiling reflects 20% more — fewer watts daytime. West blackout roller cuts 3pm glare so task works.

FAQ

Why bright room still feels dull? Single overhead + dark walls + no accent. Same 3,000lm split panel + spots + lamp + light rug + lit texture = 2x lively.

Calculator app or sheet? Sheet with lux table above + phone lux verify — apps hide assumptions + push products. Apps for plan visual, sheet for counts + bill.

Power bill and dimmer payback in numbers

Ain Borja 900 sq ft right-sized 180W LED versus neighbor 350W over-lit: 6h/day x30 days x MAD 1.2/kWh = MAD 39 versus MAD 76 monthly. Yearly save MAD 444 + fewer headaches + no hotel glare. Dimmers MAD 70 x3 (living + dining + bedroom accent) enable movie/guest/sleep same installed lumens — payback 5 months versus rewiring later MAD 260/point cut.

Voltage protection: branded drivers + surge DB MAD 600 one-time saves 6 spots yearly (MAD 240) + strips (MAD 300) from fluctuation deaths. Cheap bare tape dies 6 months, mid aluminium 4 years. Keep bill + models photo — driver warranty 2 years needs it. Daylight sheer + light quartz + white ceiling harvests 20% free daytime lumens.

How many spots for 12-ft dark hall? Three 7W 4000K spaced 3.5 ft + mirror wash = 1,950lm for 3.3 sqm x150 lux + loss. Single end tube 18W gives 1,700lm center only with tunnel corners dark. Spacing evens ±15% versus center ±60% with same watts.