Lighting Calculator
Size a room’s ambient light with the lumen method — total lumens from area and purpose, then the number of fixtures at your chosen output per light.
Lighting needed
Total lumens is the 150 lux target × 20m². Fixtures round up so you don’t fall short. Treat this as ambient (general) lighting — add task lights over counters and desks and accent lights for the mood a loft usually wants.
Getting the light level right
A room that’s under-lit feels gloomy and cramped; one that’s over-lit feels like an office. The lumen method takes the guesswork out of the middle ground: pick the illuminance a space is meant to have, multiply by its area, and you know the total light output to aim for before you buy a single fitting.
Because modern LEDs are rated in lumens rather than watts, this maps straight onto what’s printed on the box. Divide the total by one fixture’s output to see how many you need — then layer in task and accent lighting, which is where a loft’s character really comes from.
Frequently Asked Questions
How many lumens does a room need?
Multiply the floor area by the recommended illuminance for the room's purpose. A 20 m² living room at 150 lux needs about 3,000 lumens; the same room as a home office at 400 lux needs 8,000. The calculator applies the right lux target for each room type.
What is the lumen method?
It's the standard first-pass approach to lighting a space: total lumens equals target illuminance (in lux) times floor area (in m²). It sizes the overall ambient light in a room. Task and accent lighting are layered on top of that baseline.
What lux level should each room be?
This calculator uses common guidance: about 100 lux for a bedroom, 150 for a living room, 200 for dining and bathrooms, 300 for a kitchen, and 400 for a home office or study. Brighter, more detailed tasks want more light.
How do I turn lumens into a number of fixtures?
Divide the total lumens by the output of one fixture. If a room needs 3,000 lumens and each light gives 800, that's four fixtures (rounded up). Check the lumen rating on the bulb or fitting — watts no longer tell you brightness with LEDs.
Why do open-plan lofts need extra thought?
An open loft blends zones with different needs — a bright kitchen next to a softer living area — so lighting the whole footprint to one level rarely feels right. Calculate each zone separately and layer dimmable and task lighting so one space can be bright while another stays relaxed.
Estimates for planning — not professional real-estate, architecture, or financial advice. For wiring and fixed installations, consult a qualified electrician.