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Lux to lumens calculator

Convert a target illuminance in lux into the total light output in lumens a space needs. Lux measures brightness on a surface (lumens per square metre); this tool multiplies your target lux by the floor area and divides by a utilisation factor for real-world losses, then estimates the bulb count.

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The Lux to lumens calculator turns Target illuminance (lux), Area / dimension unit, Length, Width, Utilisation factor, Lumens per bulb into Total lumens needed, Floor area (m²), Bulbs needed, instantly and for free. For instance, with Target illuminance (lux) = 300, Area / dimension unit = Meters (length × width), Length = 5, Width = 4, Utilisation factor = Ideal — 100% and Lumens per bulb = 800 it returns Total lumens needed = 6,000, Floor area (m²) = 20 and Bulbs needed = 8.

How to use it

  1. Enter your values: Target illuminance (lux), Area / dimension unit, Length, Width, Utilisation factor, Lumens per bulb.
  2. Read the result instantly: Total lumens needed, Floor area (m²), Bulbs needed.

Frequently asked questions

What does the Lux to lumens calculator actually compute?

It takes Target illuminance (lux), Area / dimension unit, Length, Width, Utilisation factor and Lumens per bulb and derives Total lumens needed, Floor area (m²) and Bulbs needed from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

6 values: Target illuminance (lux), Area / dimension unit, Length, Width, Utilisation factor and Lumens per bulb. Nothing else is required — no account, no file upload.

Can you show a worked example?

With Target illuminance (lux) = 300, Area / dimension unit = Meters (length × width), Length = 5, Width = 4, Utilisation factor = Ideal — 100% and Lumens per bulb = 800, the calculator returns Total lumens needed = 6,000, Floor area (m²) = 20 and Bulbs needed = 8. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Target illuminance (lux) = 600, Area / dimension unit = Feet (length × width), Length = 10, Width = 8, Utilisation factor = Typical room — 80% and Lumens per bulb = 1,600 instead, Total lumens needed goes from 6,000 to 5,574 — which is why it is worth testing a few scenarios rather than trusting a single figure.

Which “Area / dimension unit” option should I choose?

You can pick between « Meters (length × width) » and « Feet (length × width) ». Each one changes what the calculator works out, so switch and compare — the default is « Meters (length × width) ».

What does it give for smaller values?

Scaled down to Target illuminance (lux) = 150, Area / dimension unit = Meters (length × width), Length = 3, Width = 2, Utilisation factor = Ideal — 100% and Lumens per bulb = 400, Total lumens needed comes out at 900. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Sizing what a room has to hold or produce: how many boxes a move needs and what size storage unit holds them, whether a piece of furniture clears the space, and how much light the room needs for what happens in it.

What is the most common mistake?

Sizing storage by floor area alone. Units are stacked to the ceiling in practice, so height changes the answer as much as footprint does — and access space has to be left in front.

What is the difference between the Lux to lumens calculator and the Room lighting calculator?

This one returns Bulbs needed; the Room lighting calculator returns Bulbs / fixtures needed. That is the whole difference — open the one whose figure you need.

Where do the figures come from, and how current are they?

The geometry is exact for the dimensions you enter. Standard box and unit sizes differ between the US and Europe, and the tool shows both rather than converting one into the other.

Further reading

All guides →
ExplainerLux and Lumens: The Difference, and How to Convert Between ThemLumens are what a lamp emits; lux is what lands on a surface. You cannot convert one to the other without an area, or without a distance and a beam angle. Anything that offers you a bare conversion factor is selling you a fiction.ExplainerOne Lux Figure for a Whole Room Is a Starting Point, Not a PlanA 20 m² living room at 200 lux needs 4,000 lumens, or five 800-lumen bulbs. Apply a kitchen worktop's 500 lux to the same floor and it asks for thirteen — which is the moment to stop lighting rooms and start lighting tasks.ExplainerThe Bulb Worth Changing Is the One That Is OnTen 60 W bulbs on five hours a day cost 219 a year; the same ten in 9 W LED cost 32.85, a saving of 186.15. Cut the hours to one and the saving falls to 37.23 — the hours matter more than the wattage.ExplainerA Conversion Factor Has to Be CubedA patch 12 ft by 10 ft at 4 in deep is 40 cubic feet, which is 1.48 cubic yards — dividing by 27, not by 3. The same trap in metric is dividing by 100 where a million belongs.How-toHow to Calculate Pool Volume: A Formula per Shape, and the Depth TrapLength × width × average depth gives 21,065 gallons for a 32 by 16 ft pool. But average depth only means (shallow + deep) ÷ 2 when the floor slopes evenly, and most pools do not. Here is every shape formula and the correction.How-toHow Many Moving Boxes You Need — and Why the Mix Beats the TotalA two-bedroom home comes out at 56 boxes: 14 small, 21 medium, 12 large, 4 wardrobe, 5 dish. The total is the least useful number on the page — here is why the split matters, and what the count leaves out.