Room Lighting Calculator

Written byOleh Soloninupdated 25 September 2026

Room area, m²

Purpose

Output per lamp, lm

Lamp type

Advanced options

Share of the light reaching the floor or desk

1 if you assume every lumen reaches the working plane. The real utilisation factor depends on the fitting and on how light the walls are; the maker's tables give it.

Result

Lamps needed7
Flux required, lm4,829
Target illuminance, lx200
Total wattage, W74.7
Watts per m²4.15
Maintenance factor
0.7455 = 0.71 × 1.05 — SP 52.13330, table 4.3 with note 4 for LEDs; the norm is 200 lx on the floor
Working
Φ = 200 × 18 ÷ (0.7455 × 1) = 4,829 lm; 4,829 ÷ 800 = 6.04 → 7

From what the room is for to how many fittings

Works out the flux and the number of lamps a room needs under Russia's SP 52.13330.2016 as amended in 2022 — 200 lx for living rooms and kitchens, 100 lx for corridors and bathrooms, 500 lx for a study — with a maintenance factor of 0.71, or 0.7455 for LEDs.

The calculator uses the Russian lighting code, SP 52.13330.2016. Its table L.1, as amended by Amendment No. 2 in force since 29 January 2022, gives living rooms and kitchens 200 lx and corridors, bathrooms and toilets 100 lx, measured on the floor. For a study it takes the office figure — 500 lx of general lighting on the desk, 0.8 m up. Other countries publish their own norms, so treat these as the Russian ones.

The norm has to hold years later, when the lamps have dimmed and gathered dust. So a new installation is sized with a margin: the illuminance is divided by the maintenance factor: 0.71 for living rooms under table 4.3 of the same code, and 0.71 × 1.05 = 0.7455 for LED fittings under note 4 to that table. For an 18 m² living room lit by LED lamps that is 200 × 18 ÷ 0.7455 = 4,829 lm.

How to use

Enter the room's area and choose its purpose — the norm fills in by itself.
Enter one lamp's output from the box and the lamp type.
Read the flux needed, the number of lamps and their total wattage; the advanced fields let you set the share of light that reaches the floor.

How many 800 lm lamps a room needs

Each row is a separate run: 800 lm LED lamps at 75 lm/W, with all the light reaching the working plane.

All rows come from the calculator on this page.
Room	Area	Norm	Flux needed	Lamps	Wattage
Living room	18 m²	200 lx	4,829 lm	7	74.7 W
Bedroom	12 m²	200 lx	3,219 lm	5	53.3 W
Kitchen	10 m²	200 lx	2,683 lm	4	42.7 W
Bathroom	5 m²	100 lx	671 lm	1	10.7 W
Corridor	8 m²	100 lx	1,073 lm	2	21.3 W
Study	12 m²	500 lx	8,048 lm	11	117.3 W

How much of the light reaches the floor

By default the calculator assumes every lumen reaches the floor or desk. In practice the fitting, walls and ceiling absorb part of it; lighting designers call the remaining share the utilisation factor and take it from the maker's tables. Set it to 0.5 and an 18 m² living room needs 9,658 lm — 13 lamps of 800 lm.

What this calculator shows

The illuminance norm for the chosen room
The flux needed, maintenance factor included
The number of lamps and their total wattage
Watts per square metre

What to keep in mind

Norms: table L.1 of SP 52.13330.2016 as amended by Amendment No. 2; the maintenance factor of 0.71 is from table 4.3 for living rooms, offices and classrooms, multiplied by 1.05 for LED fittings under note 4 to that table.
Lamp efficacy is the low figure from Wikipedia's "Luminous efficacy": 75 lm/W for LED, 46 for fluorescent, 16.7 for halogen and 13.8 for incandescent.

FAQs

What illuminance does a living room need?

200 lx on the floor under table L.1 of Russia's SP 52.13330.2016, as amended by Amendment No. 2 in force since 29 January 2022. Kitchens get the same; corridors, bathrooms and toilets 100 lx. Before the amendment the figures were 150 and 50 lx.

How many lamps does a 10 m² kitchen need?

At the 200 lx norm and the LED maintenance factor of 0.7455, 2,683 lm — four 800 lm lamps.

What is a maintenance factor?

The ratio of illuminance at the end of the installation's service period to that at the start: it covers the lamps' falling output and dirt on fittings and room surfaces. SP 52.13330 gives 0.71 for living rooms, offices and classrooms, and 0.71 × 1.05 = 0.7455 for LED fittings (note 4 to table 4.3).

Why does the study get 500 lx?

Table L.1 has no line for a study at home. The calculator uses the figure for offices and workrooms in administrative buildings — 500 lx of general lighting at 0.8 m.

Does ceiling height matter?

Not to the norm, which is set on the floor or desk. Height changes how much light reaches that plane — set that share under the advanced fields.

How many watts per square metre does lighting take?

For an 18 m² living room with 800 lm LED lamps, 4.15 W/m²; with 1,340 lm incandescent lamps, 21.58 W/m². The figure depends on the lamps as much as on the norm.

Worked example

An 18 m² living room

Input: 18 m², 800 lm lamps

Output: 4,829 lm — 7 lamps

Note: At 75 lm/W the LED lamps draw 74.7 W together — 4.15 W per square metre.

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