Calculate the lumens your room needs
Enter the room in feet. Lux targets follow the standard Indian residential recommendations.
How this calculator works
This is the lumen method, the standard approach used in lighting design, with the two factors that people usually leave out:
- Area in square metres = length × width × 0.092903. Lux is defined per square metre, so the conversion has to happen first.
- Utilisation factor (UF) accounts for light absorbed by walls, ceiling and floor before it reaches the working plane. Light finishes 0.65, mid-tone 0.60, dark 0.50.
- Maintenance factor (MF) accounts for dust on the fitting and lumen depreciation over life. 0.80 in a normal flat, 0.70 in a dusty roadside location.
- Lumens = lux × m² ÷ (UF × MF).
- Wattage = lumens ÷ efficacy. Budget LED 80 lm/W, standard 100, premium 120.
- Fitting count is then lumens divided by the output of a single fitting, rounded up — 900 lm for a 9 W downlight, 1,200 lm for a 12 W.
| Room | Target lux | Lumens for a 120 sq ft room | Layer it needs |
|---|---|---|---|
| Bedroom, general | 100 lux | 2,320 lm | Ambient plus bedside task |
| Living room, general | 150 lux | 3,480 lm | Ambient, accent on art, a floor lamp |
| Dining | 200 lux | 4,640 lm | Pendant over the table plus ambient |
| Bathroom | 200 lux | 4,640 lm | Ambient plus shadow-free mirror light |
| Kitchen, general | 300 lux | 6,960 lm | Ceiling grid plus under-cabinet strips |
| Study / home office | 400 lux | 9,280 lm | Ambient plus a dedicated desk task light |
| Kitchen counter, task | 500 lux | 11,600 lm | Under-cabinet LED strip, always |
Task figures apply to the work surface only, not to the whole room — light the counter, not the ceiling above it.
Design and build under one accountable roof
Worked example: a 12 × 12 ft living room
- Area = 144 sq ft = 144 × 0.092903 = 13.38 m²
- Target for a living room = 150 lux
- UF 0.60 (mid-tone walls) × MF 0.80 (clean flat) = 0.48
- Lumens = 150 × 13.38 ÷ 0.48 = 4,181 lumens
- At 100 lm/W that is 42 W of LED in total
- Delivered as 9 W downlights at 900 lm each: 5 fittings; as 12 W at 1,200 lm: 4 fittings.
Why one number is not a lighting design
A room that hits 150 lux from a single ceiling grid is correctly lit and looks terrible. The lumens figure tells you the budget; how you spend it decides whether the room is pleasant. Our working split for a living room is roughly 50% ambient — cove or downlights on a dimmer — 30% task, which is reading and side lamps, and 20% accent on art, texture and plants.
Two practical notes for Indian homes. First, colour temperature: 2700–3000K in bedrooms and living rooms, 4000K in kitchens and utility, and never mix the two within one sightline. Second, dimming: specify a trailing-edge dimmer and confirm the driver is dimmable before the ceiling closes, because retro-fitting a dimmable driver above a finished gypsum ceiling means cutting it open.
What this calculator does not do
- It does not position fittings — use the downlights calculator for count, grid and spacing
- It assumes a general ambient layer, not a task-lit work plane at a specific height
- It does not model daylight contribution, which can be large in a west-facing Mumbai flat
- It does not cover glare, beam angle or colour rendering index, all of which matter at specification stage
- It does not price the fittings, wiring or drivers
This calculator uses the same rate bands and site rules our estimators apply, taken from Greenbox project records and cross-checked against 2026 supplier and contractor quotations in Mumbai. It is an indicative estimate, not a quotation — the real figure depends on your drawings, site condition and the brands you finally specify.
Three layers, and what each one is for
- Ambient. The base level that lets you move through the room safely and see faces clearly. Cove lighting, ceiling downlights on a dimmer, or a central fitting in a bedroom. This is where most of the lumens on this page go.
- Task. Light delivered to a surface where something is being done — a kitchen counter, a desk, a bedside book, a mirror. Task light is measured at the surface, not at the ceiling, and it is why a 500 lux counter target does not mean the whole kitchen needs 500 lux.
- Accent. Three times the surrounding level on the thing you want noticed: a picture, a stone panel, a plant, a texture. Accent lighting is what makes a room look designed rather than merely lit, and it costs almost nothing in watts.
A practical split for a living room is 50% ambient, 30% task and 20% accent. Wire each layer to its own switch. A room with one switch has one mood; a room with three has six, and no extra fittings were needed to get there.
Lux targets against real Indian rooms
Two corrections to the standard tables are worth making for Indian homes. First, kitchens: the 300 lux general figure assumes you are also getting 500 lux at the counter from under-cabinet strips. Without those strips you are standing in your own shadow whatever the ceiling does, and no amount of downlight count fixes it. Second, pooja rooms and dressing areas both need higher levels than their size suggests — 200 to 300 lux — with high colour rendering, because both are places where you are judging colour rather than navigating a space.
Selected work by Greenbox Design Studio. Tap any image to enlarge.
Frequently asked questions
How many lumens do I need for a living room?+
About 30 lumens per square foot of delivered light, so a 144 sq ft living room needs roughly 4,200 lumens — around 42 W of LED. That assumes a 150 lux target with mid-tone walls. Dark walls or wood panelling push it closer to 5,000 lumens.
What is the difference between lux and lumens?+
Lumens measure the total light a fitting emits. Lux measures how much of that light lands on a surface — one lux is one lumen per square metre. You set a lux target for the room and then buy enough lumens to reach it after losses.
Why divide by a utilisation and maintenance factor?+
Because not all the light a fitting emits reaches the working plane. Some is absorbed by walls, ceiling and floor, which is the utilisation factor. More is lost to dust and to LED output declining over life, which is the maintenance factor. Together they typically cost you about half the raw lumens.
How many watts of LED does a 2BHK need?+
Usually 250–350 W of connected LED across the whole flat, delivered across ambient, task and accent circuits. That is a fraction of what the same flat drew on CFL and tube lights, which is why lighting is one of the few places in a fit-out where the better specification is also the cheaper one to run.
What colour temperature should I use?+
2700K to 3000K in bedrooms and living rooms, 4000K in kitchens, utility and bathrooms where you want the light to read as clean. Keep a single temperature within one sightline — an open-plan living and kitchen with 3000K on one side and 4000K on the other looks like a fault, not a design.