Room Lux Calculator: Lumens by Room, Sq Ft & Sq M

How to use the lux calculator

Enter the length and width of the room (or of the area you want to light) in metres or feet.
Pick the closest room or task to fill in a reference illuminance, or type your own target in lux.
Leave the utilisation and maintenance factors at 1 for a quick minimum, or enter values from the light fitting’s datasheet or a lighting designer.
Optionally enter the lumens of one light fitting to see how many fittings that takes.

Formula

The calculator uses the lumen method:

Φ = E × A ÷ (UF × MF)

Φ: total luminous flux needed from all fittings, in lumens (lm)
E: target average illuminance on the working plane, in lux (lx = lm/m²)
A: area, in m² (feet are converted with 1 ft = 0.3048 m)
UF: utilisation factor, the share of the lamps’ light that reaches the working plane
MF: maintenance factor, the share of light left after lamps age and fittings get dirty

Number of fittings = Φ ÷ lumens per fitting, rounded up. The illuminance reached with that whole number of fittings is (fittings × lumens per fitting × UF × MF) ÷ A.

Units

Illuminance in lux (lx); 1 footcandle (fc) = 1 lm/ft² ≈ 10.764 lx. Light output in lumens (lm). Area in square metres (m²) or square feet (ft²).

Recommended lux by home room (sq m and sq ft)

These are commonly cited guideline ranges for homes, attributed to the IES (Illuminating Engineering Society, formerly IESNA). We have not reproduced the IES Lighting Handbook itself, and published tables differ, especially for bedrooms and kitchens, so treat them as typical guidance rather than a standard. Penn State’s course notes, for example, give about 10–20 footcandles (roughly 108–215 lux) for living rooms and 50–100 footcandles for kitchen task areas (source). Lumens per area are simply lux × area (UF = MF = 1), so they are a minimum.

Room	Guideline (lux)	Lumens per m²	Lumens per ft²	Example: 20 m² (215 ft²)
Living room	100–200	100–200	9.3–18.6	2,000–4,000 lm
Kitchen	300–500	300–500	27.9–46.5	6,000–10,000 lm
Bedroom	100–150	100–150	9.3–13.9	2,000–3,000 lm
Office / work area	400–500	400–500	37.2–46.5	8,000–10,000 lm

1 footcandle = 1 lm/ft² ≈ 10.764 lx. Choosing a home room in the calculator loads the middle of its range and shows the lumen range for your room size.

Reference illuminance values

EN 12464-1 sets maintained illuminance values (Ēm) for workplaces. The “modified” value is the higher level the standard suggests when, for example, the task is visually demanding or the people doing it have reduced vision. These are the values offered in the calculator:

Room or task	Required Ēm (lx)	Modified Ēm (lx)	Reproduced by
Circulation areas, corridors	100	150	Glamox
Washrooms, bathrooms, toilet areas	200	300	Glamox
Archiving	200	300	Signify code finder
Filing, copying	300	500	Signify code finder
Reception desk	300	750	Signify code finder
Writing, typing, reading, data processing	500	1000	Signify code finder
Conference and meeting rooms	500	1000	Signify code finder
Technical drawing	750	1500	Signify code finder

The standard does not cover homes. For a room at home you can use a similar task as a reference (a desk for reading, for example, is close to “writing, typing, reading”) or set your own target.

Two-way workflow: calculate bulb wattages from total lumens

Sources

Limits of this calculator

The result is an average over the whole area. The lumen method says nothing about how evenly the light is spread, glare or colour rendering, which the standard also sets requirements for.
With UF and MF left at 1 the result is a lower bound: in a real room some light is absorbed by walls and ceiling, and output drops over time.
The standard values are reproduced from the manufacturer pages listed above, not from the standard text. If you must comply with EN 12464-1, check the edition that applies to you and its full tables.
It cannot measure the light in your room; only a calibrated lux meter can.

Frequently asked questions

How do I calculate the lumens a room needs?

Multiply the target illuminance in lux by the floor area in square metres (lumens = lux × m²). In square feet, lumens = footcandles × ft², where 1 footcandle ≈ 10.764 lux. Divide by the utilisation and maintenance factors if you know them. For example, a 4 m × 3 m living room at 150 lux needs at least 150 × 12 = 1,800 lm.

How many lux does a living room, kitchen or bedroom need?

Commonly cited guideline ranges attributed to the IES are 100–200 lux for a living room, 300–500 lux for a kitchen, 100–150 lux for a bedroom and 400–500 lux for an office or work area. Published tables differ, especially for bedrooms and kitchens, so these are typical guidance, not a legal requirement.

How do I convert lumens to watts for an LED bulb?

Divide the lumens you need by the bulb’s luminous efficacy in lumens per watt (watts = lumens ÷ lm/W). Use the lumens and watts printed on the bulb’s packaging for the true figure. The Lumens to Watts Calculator does this for LED, CFL, halogen and incandescent bulbs.

How many LED bulbs do I need for a room?

Divide the total lumens by the lumens of one bulb and round up. Enter the lumens of one fitting in the calculator and it does this for you and shows the average lux you would actually reach.

What are the limits of this calculator?

It gives an average over the floor area, assumes the factors you enter, and cannot measure real light. Only a calibrated lux meter can show the light in your room.

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This tool runs entirely in your browser and does not send or save what you enter. It calculates from your numbers only; it cannot measure a real lamp, battery or room. Affiliate disclosure: some articles on this site may contain affiliate links; this tool contains none. Learn more.

Last updated: 2026-10-15