How the Light Plan calculates

An estimate, not a specification

This is an estimate based on a standard 2.4–2.6 m ceiling and light-coloured matt walls. A room with dark walls, a high ceiling, or a lot of dark furniture will need more light than the figure below; a small pale room will need less. Treat it as a starting point, not a specification.

The arithmetic

The plan works out a total lumen figure in one step:

total lumens = ( floor area in m² × target lux ) ÷ utilisation factor

Floor area comes from the length and width you enter. Target lux comes from the table below. The result is rounded to the nearest 50 lm, because a lighting estimate accurate to the single lumen would be a false precision.

Utilisation factor

Not all the light a fitting emits arrives where you want it. Some is absorbed by the shade, some by the walls, some by dark furniture. We divide by a utilisation factor to account for that:

0.65 indoors — a conventional domestic figure for a room with light-coloured matt walls and a normal ceiling.
0.8 outdoors — nothing reflects light back to you, but outdoor fittings are direct rather than shaded, so less is lost inside the fitting itself.

A room with dark walls has a materially lower utilisation than 0.65. If your walls are dark, add roughly a third to whatever the plan tells you.

Target illuminance by room and purpose

Figures in lux. These are working targets for domestic rooms, set at the lower end of what an office standard would ask for — a living room lit to an office specification is unpleasant to be in.

Room	Ambient	Reading	Close work	Mixed	Colour temp	IP requirement
Living room	100 lx	300 lx	500 lx	200 lx	2700 K	No IP requirement
Bedroom	75 lx	250 lx	400 lx	150 lx	2700 K	No IP requirement
Kitchen	150 lx	250 lx	500 lx	300 lx	3000–4000 K	No IP requirement
Desk & study	150 lx	400 lx	600 lx	400 lx	3000–4000 K	No IP requirement
Hallway	100 lx	150 lx	200 lx	150 lx	2700 K	No IP requirement
Bathroom	150 lx	200 lx	400 lx	250 lx	3000 K	IP44 or better only
Outdoor	30 lx	100 lx	150 lx	50 lx	2700 K	IP44 or better only

How many separate fittings

One bright fitting and several smaller ones producing the same total are not the same room. The plan divides the total across separate sources:

Ambient, reading and mixed — one source per 7 m², capped at five. A 25 m² living room therefore gets four.
Close work — one or two, because the target is a work surface rather than a room.

The three safety filters

These run before any scoring or ranking. They do not push articles down a list; they remove them from consideration entirely.

Filter 1 — wiring

Answer “no” to the wiring question and every hard-wired article is excluded by name. There is no ranking involved and no way for one to slip through. These are the 13 articles that the plug-in branch excludes:

Filter 2 — IP rating

Choose bathroom or outdoor and only articles rated IP44 or better remain. An article with no IP rating on file is removed, not shown with a warning — for a wet room the warning is not enough.

Filter 3 — colour rendering

Choose close work and only articles where we hold a colour rendering test report at Ra 90 or above remain. Articles with no test report are removed rather than assumed adequate. That leaves 8 articles available for close work:

How articles are chosen once the filters have run

What is left is scored, and the highest-scoring article becomes the main source. The score rewards:

Output close to the per-fitting share of the total, so the room ends up even.
A narrow beam (60° or less) when the purpose is reading or close work; a wide beam (100° or more) when it is ambient.
Colour rendering on file, for reading and close work.
A category that suits the room — pendants over kitchen islands, table lamps beside beds, wall lights in hallways.

A second, different article is then added to fill the remainder, so the plan is layered rather than four copies of one lamp. If any chosen fitting ships without a bulb, a matching bulb is added and labelled as such.

What the plan will tell you when it cannot help

If the filters leave nothing at all, it says so, and says that this is a real answer rather than an error.
If the articles available reach less than 70% of the target, it prints the gap in lumens rather than hiding it behind a confident-looking result.
Every filter that ran is listed on the result, in plain words.

What it does not do

It does not account for ceiling height, wall colour, floor colour or furniture. Those matter, and the disclaimer at the top says so.
It does not model glare, uniformity, or how light falls on a face.
It is not a lighting design, and it is not a substitute for one on a large room.
It makes no claims about what light does to a body — see electrical safety for what we do not claim and why.

If your room is unusual, send it to us. We will tell you what would work, including when the answer is not something we sell.

Questions about this page

Email support@mazodesign.shop or call +45 31685249. Monday–Friday, 09:00–16:00 CET. Email is answered within 1 business day.