ParrotNotes

Lumens Calculator

Work out the lumens a room needs from its size and use, then the number of fixtures or bulbs, with foot-candles or lux and a watts-to-lumens check. Pick a room type or type your own target, add the lumens per fixture and the factors if you have them.

Your numbers

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Targets from UFC 3-530-01, the US Defense Department's lighting criteria written to the IES's recommendations.

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Foot-candles (lumens per sq ft) on the work surface. Type your own to override the room type.

Lumens needed

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Target
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Area
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In 800 lumen bulbs
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The calculation runs in your browser and ParrotNotes does not store your numbers. They sit in the page address so you can bookmark or share the result.

How the lumens are worked out

Illuminance is light per area: a foot-candle is one lumen per square foot. So the lumens a room needs on its work surface are the floor area × the foot-candles you want there. A 200 sq ft room at 30 foot-candles needs 6,000 lumens; at 5 foot-candles, 1,000.

That is the light that has to arrive, not what the bulbs put out. Some of a fixture's light lands on the walls and ceiling or is lost in the fixture, and output drops as lamps age and gather dirt. The fixtures mode lets you allow for both.

Where the foot-candle targets come from

The room types use UFC 3-530-01, Interior and Exterior Lighting Systems and Controls (February 2023, Change 1 of December 2023), the Defense Department's lighting criteria, written to meet the Illuminating Engineering Society's recommendations. It gives an average horizontal illuminance for each space: 30 foot-candles for offices and meeting rooms, 40 for classrooms, 5 for corridors, and 5 to 20 for warehouses depending on the size of the items.

Its housing values are general light for the room: 3 foot-candles for a living room, 5 for a bedroom, 30 at a bathroom vanity and a kitchen's cooking surface. Reading, cooking and close work need more on that surface, which is why task lights and under-cabinet lights exist. Type your own target if the job calls for one.

Light levels by room

UFC 3-530-01's average horizontal illuminance for each room type, and the lumens 100 sq ft of it needs before any losses. Scale by your area: 250 sq ft needs 2.5 times as many.

Target foot-candles, lux and lumens per 100 square feet by room type
RoomTargetLumens per 100 sq ft
Home: living room, general3 fc (32 lux)300 lm
Home: bedroom5 fc (54 lux)500 lm
Home: dining room5 fc (54 lux)500 lm
Home: hallway3 fc (32 lux)300 lm
Home: kitchen, cooking surface30 fc (323 lux)3,000 lm
Home: bathroom, vanity height30 fc (323 lux)3,000 lm
Home: laundry room20 fc (215 lux)2,000 lm
Home: rec room20 fc (215 lux)2,000 lm
Home: garage20 fc (215 lux)2,000 lm
Work: private office30 fc (323 lux)3,000 lm
Work: open office30 fc (323 lux)3,000 lm
Work: meeting room30 fc (323 lux)3,000 lm
Work: classroom or training room40 fc (431 lux)4,000 lm
Work: break room or lounge10 fc (108 lux)1,000 lm
Work: large lobby10 fc (108 lux)1,000 lm
Work: corridor5 fc (54 lux)500 lm
Work: restroom, general5 fc (54 lux)500 lm
Work: storage room10 fc (108 lux)1,000 lm
Work: mechanical room20 fc (215 lux)2,000 lm
Work: commercial kitchen, prep surface50 fc (538 lux)5,000 lm
Work: vehicle maintenance bay30 fc (323 lux)3,000 lm
Work: maintenance shop, general30 fc (323 lux)3,000 lm
Warehouse: small items20 fc (215 lux)2,000 lm
Warehouse: medium items10 fc (108 lux)1,000 lm
Warehouse: large items, infrequent use5 fc (54 lux)500 lm

From lumens to fixtures

The lumen method divides the lumens needed by the lumens each fixture delivers to the work plane. UFC 3-530-01 defines the two factors: the coefficient of utilization, the share of the lamp's light that reaches the work plane, and the light loss factor (formerly called maintenance factor), the drop from dirt and lamp depreciation. It gives 0.81 as a typical light loss factor for an office with LED fixtures rated L80 at 60,000 hours.

Both factors are optional here and left out when blank, which gives the fewest fixtures that could work. For a real layout, take the coefficient of utilization from the fixture's photometric report and check spacing so the light is even, not just the average.

Watts to lumens

Watts are power, lumens are light. Lumens = watts × efficacy (lumens per watt). The calculator uses typical efficacies you can change: LED 80, CFL 67, halogen 20 and incandescent 16, from the U.S. Energy Information Administration and the University of Maryland Extension. ENERGY STAR's table turns the result into the old incandescent bulb most people still think in.

For lighting reps and electricians on a site survey

On the walk-through, note each room's size and ceiling height, what it is used for, the fixtures there now and their lumens, what the customer wants better, where the switches and controls are, and any light level the spec or the tenant asks for. Read the room list back before you leave, so the fixture count in the quote matches the building.

Sources, each read on 2026-10-30. Results are estimates of the average light, not a lighting layout:

Working out what the new lights cost to run, or measuring an odd-shaped room? Try the electricity cost calculator or the square footage calculator.

More for electrical and home services sales: Electrical distributor sales, Home improvement sales.

The lighting job is won on the site survey

Room sizes, ceiling heights, the fixtures there now and what the customer wants lit better all come up on the walk-through. Record it in ParrotNotes and get a transcript, a summary and the action items, so the fixture count in the quote matches the rooms you walked.

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