Nova Light Shop — Home LED Bulb Selection | novalightshop.com
Four steps: measure the floor area, pick a target lux, multiply to get lumens, divide by one bulb's output to get the bulb count.
Start by measuring the floor area in square metres — length times width. This is the only measurement you take; everything else comes from published lux targets.
Pick the target lux that matches how the surface is used: 50 lx for family living-room ambient lighting (Australia, 1998), 100 lx for corridor-level light, 320–500 lx for office and work surfaces, and 500 lx for a kitchen worktop. A single fixture of 12000 lumens is published as lighting a home kitchen to 500 lx.
On narrow screens, swipe or scroll the plate sideways.
Multiply area by lux to get the lumens the room needs. A 12 m² room at 500 lx needs 6000 lumens; the same room at 50 lx needs 600 lumens. One lux is one lumen per square metre, so 1000 lumens over 1 m² give 1000 lx and over 10 m² give 100 lx.
Divide the total by the lumens of one bulb to get the bulb count. If the package states 1500 lumens, a 6000-lumen room needs four bulbs.
Three failure modes cause a room that still reads dim after the bulb change. Sizing by watts instead of lumens: an incandescent lamp runs at 10–17 lm/W (about 16 lm/W at 120 V, 13 lm/W at 230 V) while a typical white LED runs near 100 lm/W, so swapping watt for watt underlights the room. Forgetting the cosine loss: illuminance falls with the cosine of the angle between the light direction and the surface normal, so light aimed at a wall or a sloping ceiling delivers less lux to the working surface than the package suggests. And one central fixture spreading the same flux over too large an area: the lumens are unchanged, but the lux on each square metre drops.
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