A flush mount light is sized from the room, not the ceiling: add the room's length and width in feet and read the total as inches of diameter, so a 10 by 12 foot bedroom takes a 22 inch fixture. Keep the lowest point 7 feet above the floor. What size ceiling light does each room need? Add the room's length and width in feet and read the total as inches. A 12 by 10 foot room sums to 22, so a fixture around 22 inches across suits it. Room (length × width) Area Diameter Rooms this fits 8 × 10 ft 80 sq ft 16–18 in Powder room 10 × 12 ft 120 sq ft 20–24 in Bedroom 12 × 14 ft 168 sq ft 24–28 in Primary bedroom 14 × 18 ft 252 sq ft 28–34 in Living room 16 × 20 ft 320 sq ft 32–38 in Open plan Lumens' sizing guide publishes that ladder as a quick-reference table, and under 100 square feet the answer is 12 to 16 inches. The Alabaster Square Flushmount Ceiling Light covers four rungs of it — 12, 16, 20 and 24 inch squares, $395 to $1,095. How wide should a flush mount light be in a hallway? One third to one half of the corridor's width, and no more. Hallway width One third One half Diameter to buy 3 ft (36 in) 12 in 18 in 12–18 in 3 ft 6 in (42 in) 14 in 21 in 14–18 in 4 ft (48 in) 16 in 24 in 16–24 in 5 ft (60 in) 20 in 30 in 20–24 in A hallway breaks the rule: a 20 foot run 3 feet wide sums to 23 inches, two thirds of the corridor. mirodemi's hallway guide sets the band at 16 to 24 inches for a 4 foot hallway, and City Lights SF puts hallways at 12 to 18. Three feet is the narrowest hall the code allows, which is why the Chiara Smoke Glass Flushmount starts at 17 inches, from $948. How far should a semi flush mount ceiling light drop below the ceiling? Ceiling height in inches minus the fixture's total drop — canopy, body and finial — has to land at 84 inches or more wherever people walk underneath. Ceiling height Longest drop Supplier guidance Body to look for 7 ft 6 in (90 in) 6 in 2–4 in Flush, no stem 8 ft (96 in) 12 in 8–10 in Flush to short semi-flush 9 ft (108 in) 24 in 12–18 in Semi-flush with a stem 10 ft (120 in) 36 in 18–24 in Semi-flush, or short pendant Read it as arithmetic, not advice: 96 minus 84 leaves 12, 108 leaves 24, 120 leaves 36. The code fixes the ceiling, not the fixture — 7 feet in a habitable room or hallway, 6 feet 8 inches in a bathroom, laundry room or above the treads of a stairway — so a 6 foot 8 inch laundry ceiling with a 4 inch flush mount puts the glass at 6 feet 4 inches: fine where nobody walks, wrong over a stair. The same logic sets a chandelier ceiling fan 's blades. The drop comes off the spec sheet: flush bodies here run 2 inches deep, semi-flush bodies 10 to 11¼ inches, so on an 8 foot ceiling the 12 inch allowance is the whole budget. On 9 feet the 10.25 inch Amor 2-Tier Glass Ghiaccio Round Flushmount 18" at $859 leaves 7 feet 9 inches or better, while the Ricci Flush Mount 18.5" at $469 hangs 15 inches and belongs over a table or bed. How do you check the size and clearance before you buy? Measure the room's length and width in feet, add them, and read the sum as inches. In a corridor, cap the diameter at one third to one half of the hallway width. Write the ceiling height down in inches — 8 ft is 96, 9 ft is 108, 10 ft is 120. Total the fixture's drop from the spec sheet, canopy and lowest point included. Subtract the drop from the ceiling height; in any walkway the answer must stay at 84 inches or more. Multiply the square footage by the level the room needs — 5 to 10 lumens per square foot for a hall, 20 to 30 for a laundry. In a closet, measure the storage volume: 24 inches out from the side and back walls, plus the 12 inch band under the ceiling. What size ceiling light for a closet, laundry room or storage room? Closets are the one interior where the gap between fixture and contents is written into the electrical code. NFPA 70 (NEC) 410.16 permits only surface-mounted or recessed LED and fluorescent fixtures with fully enclosed light sources, bans open-lamp fixtures and pendants, and asks for 12 inches between a surface-mounted enclosed LED fixture and the nearest point of the closet storage space — 6 inches for recessed or fluorescent types. That storage space runs 24 inches out from the side and back walls plus a 12 inch band under the ceiling, so a fixture above the door sits 12 inches clear of the top shelf. Size inside is small: 12 to 16 inches under 100 square feet. A laundry wants 20 to 30 lumens per square foot; a reach-in closet 100 to 200 lumens in total, a 6 by 8 foot walk-in 500 to 1,000. What bulb and light output does the fixture need? Shop in lumens. Multiply the room's area by the level for the room type — 5 to 10 lumens per square foot for a hallway or bedroom, 20 to 30 for a laundry, 20 to 50 for a bathroom. Those are the residential illuminance targets in IES RP-8-22 as published by LightingCalculate : a 120 square foot bedroom at 5 to 10 wants 600 to 1,200 lumens. ENERGY STAR's brightness guide translates that into hardware: a 60 watt replacement delivers at least 800 lumens, a 40 watt replacement 450. For colour, 2700K to 3000K is the residential default; the 1920s Odeon K9 Crystal Round Flushmount Chandelier ships 27 W at 19 inches and 63 W at 31 inches, $1,375 and $2,369, both at 2700K. Two labels do the rest of the work. ENERGY STAR requires every certified fixture to be evaluated with its light source installed, and UL's summary of the V2.0 programme puts minimum output between 250 lumens for decorative fixtures and 800 by type. Dimming is a property of the pair, not the fixture: ENERGY STAR's Luminaires V2.0 specification groups dimming under its control requirements, so a dimmable fixture still needs a matching dimmer from its data sheet. In a bathroom, the tub and shower zone wants a fixture marked for damp locations, or wet where it takes spray. Sources NFPA 70 (NEC), 410.16 and 210.70 — closet luminaire clearance — nfpa.org . ENERGY STAR, Learn About Brightness — energystar.gov . ENERGY STAR, Luminaires V2.0 Final — energystar.gov . UL, Luminaires V2.0 update — code-authorities.ul.com . 2021 IRC R305.1 — ceiling heights — codes.iccsafe.org . Damp and wet locations — Article 410 and UL 1598 — menifee.ca.gov . IES RP-8-22 levels — hallway 5 to 10, laundry 20 to 30 — lightingcalculate.com . Lumens, ceiling light sizing — the-edit.lumens.com . City Lights SF, size guide — citylightssf.com . mirodemi, hallway size — mirodemi.com . closetworld.com, closet lighting — closetworld.com . FAQ What size ceiling light does a 12 by 12 foot room need? 24 inches. Add 12 and 12 and read the sum as inches; 20 to 24 inches suits 144 square feet. How wide should a flush mount light be in a hallway? One third to one half of its width: 12 to 18 inches in a 3 foot corridor, 16 to 24 inches in a 4 foot one. How far can a semi flush mount ceiling light drop? Far enough to leave 7 feet to the floor — 12 inches on an 8 foot ceiling, 24 inches on a 9 foot ceiling, 36 inches on a 10 foot ceiling. What size flush mount for a closet or laundry room? 12 to 16 inches under 100 square feet, and at least 12 inches clear of the closet storage space. How many lumens does a flush mount ceiling light need? Area times the level for the room: 5 to 10 lumens per square foot for a hallway or bedroom, 20 to 30 for a laundry, 20 to 50 for a bathroom. Diameters, drops and clearances follow published sizing guidance and the arithmetic of ceiling height minus fixture drop, except where a code section is named — NFPA 70 on closets and lighting outlets, the IRC on ceiling heights. Check the fixture's spec sheet for its installed drop, and have ceiling mounting and wiring done by a licensed electrician.