Room lighting calculator
Updated
Enter your room’s size and wall color to see how many lumens and LED watts to use. Below the calculator you will find the recommended lux for every room in the house.
Calculate for your room
Lux and lumens by room
Recommended lux for each room and how many lumens a 12 m² (130 sq ft) room with light walls needs. Open a room for the full chart by size.
| Room | General room light | Color temperature | Lumens (12 m²) |
|---|---|---|---|
| Living room Reading on the sofa or armchair: 300–500 lx | 100–200 lx | 2700K to 3000K | 5,350 lm |
| Bedroom Reading in bed, mirror and wardrobe: 300–500 lx | 100–150 lx | 2700K to 3000K | 4,300 lm |
| Kitchen Countertop, sink and stove: 300–500 lx | 200–300 lx | 3000K to 4000K | 8,950 lm |
| Bathroom Mirror and vanity: 300–500 lx | 150–250 lx | 3000K to 4000K | 7,150 lm |
| Home office Desk (work or study): 500 lx | 300–500 lx | 4000K | 10,700 lm |
| Dining room Table top: 200–300 lx | 100–200 lx | 2700K to 3000K | 5,350 lm |
| Hallway Stairs and steps: 100–150 lx | 75–150 lx | 2700K to 3000K | 3,550 lm |
| Laundry room Sink and ironing: 300–500 lx | 200–300 lx | 4000K to 5000K | 8,950 lm |
How the math works
Average illuminance (lux) is the light that reaches the work plane (table height, 0.75 m / 30 in), per square meter. Not all the light a bulb emits gets there: walls and ceiling absorb part of it, and LEDs lose output over time. The math follows the lumen method, the standard lighting design calculation:
lumens = lux × area ÷ (CU × MF)
- Room index (K): describes the room's shape. K = L × W ÷ [h × (L + W)], where h = ceiling height − 0.75 m. Small rooms and tall ceilings have a low K: more light hits the walls before reaching the table.
- Coefficient of utilization (CU): how much of the light reaches the work plane. It comes from a table that crosses K with wall reflectance (light ≈ 50%, mid-tone ≈ 30%, dark ≈ 10%), for a diffuse ceiling fixture and a white ceiling.
- Maintenance factor (MF): 0.8, to account for LED depreciation and dust.
Example: in a 4 × 3.5 m room with a 2.7 m ceiling (h = 1.95 m), K ≈ 0.96 and, with light walls, CU ≈ 0.44. For 150 lux: 150 × 14 m² ÷ (0.44 × 0.8) ≈ 6,000 lumens. Divided by 95 lm/W, that is about 63 W of LED.
The 3D simulator uses the same math, with the size and wall color you pick.
Read this before you buy
These numbers are an estimate for planning and comparing, not a lighting design. The math accounts for wall color, light loss over time and an average LED efficacy (95 lm/W), but it does not know which fixture you will use, its beam angle or where the furniture is.
- In the store, compare lumens on the box, not watts. Efficacy ranges from 80 to over 110 lm/W.
- Closed fixtures, frosted diffusers and dark shades deliver less light than the bare bulb.
- When in doubt, aim for the middle of the range and add a dimmer: you can turn light down, not up.
- For construction, major renovations or commercial spaces, talk to a lighting designer, architect or electrician.
Where the values come from
The math follows the lumen method in the IES Lighting Handbook (Illuminating Engineering Society) and CIE 52 on utilization factors. The lux ranges are comfort references for homes, based on ANSI/IES RP-11 (residential lighting), ISO/CIE 8995-1 / EN 12464-1 and the residential values of the former Brazilian standard NBR 5413. Workplace lighting standards do not regulate homes; treat the values as a starting point.
- The Lighting Handbook, 10th ed. (2011)
Illuminating Engineering Society (IES) · Lumen (zonal cavity) method, room index and coefficient of utilization. - CIE 52:1982 — Calculations for interior lighting: applied method
Commission Internationale de l’Éclairage (CIE) · Utilization factor from the room index and surface reflectances. - ANSI/IES/ALA RP-11-26 — Lighting for Interior and Exterior Residential Environments
IES / American Lighting Association · Recommended practice for home lighting: lux levels per room and task. - ABNT NBR ISO/CIE 8995-1:2013 — Iluminação de ambientes de trabalho, Parte 1: Interior
ABNT (Brasil) · ISO/CIE 8995-1 · Current Brazilian/ISO standard for indoor illuminance; basis for home office and circulation areas. - EN 12464-1:2021 — Light and lighting: Lighting of work places, Part 1: Indoor
CEN (Europa) · European counterpart, same concept of maintained average illuminance. - ABNT NBR 5413:1992 — Iluminância de interiores (cancelada em 2013)
ABNT (Brasil) · Replaced by NBR ISO/CIE 8995-1; still the most quoted residential lux reference in Brazil.
Frequently asked questions
What is the difference between lux and lumens?
Lumens (lm) measure how much light a bulb emits. Lux (lx) measures how much light lands on each square meter: 1 lux = 1 lumen per m². The same 1,000-lumen bulb gives far more lux in a 4 m² bathroom than in a 20 m² living room.
How many lumens per square meter?
It depends on the room: from about 300 lm/m² in hallways and bedrooms to 900 lm/m² or more in a home office, losses included. Multiply the area by the target lux and divide by about 0.34 (a room of about 12 m² / 130 sq ft with light walls); smaller rooms and dark walls need a smaller divisor, so more lumens. Per square foot, divide those numbers by 10.8.
How do I convert watts to lumens?
For a regular LED bulb, multiply the watts by about 95: a 9 W bulb gives around 850 lumens. Efficacy varies between brands, so the reliable number is the one printed on the box.
See it before you drill the ceiling
Build the room in 3D, drag the fixtures around, change watts and Kelvin and see the result instantly.
Open in the 3D simulator