Lux to Lumens Calculator

MiniWebtool’s Lux to Lumens Calculator estimates the light output needed for a target illuminance across a room. Enter area or dimensions to see lumens, a light-loss adjustment, and an approximate bulb count.

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Help me understand MiniWebtool's Lux to Lumens Calculator: https://miniwebtool.com/lux-to-lumens-calculator/. What can I use it for, what inputs or settings do I need, and how do I use it and understand the output? Walk me through one simple example. Use this page as your source and answer in English.

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300 lux over 20 m2 = 6,000 lm, about 10 bulbs of 800 lm

Choose a room type or enter the lux level, then the room size and the bulb output. The result gives the lumens needed and the number of bulbs.

Quick examples — click to fill the form, then press Calculate:

Room type (optional)

Pick a room to load a recommended lux level — you can still edit it.

Target illuminance (lux)

How bright you want the surface to be.

Room size — enter as

Length

Width

Unit

Total floor area

Lighting quality (utilisation)

Lumens per bulb

800 lm ≈ 60 W-equivalent LED. Used for the bulb count.

Embed Lux to Lumens Calculator Widget

About Lux to Lumens Calculator

The Lux to Lumens Calculator converts a target illuminance in lux into the total lumens a room needs, using the room's area or its length and width. Beyond the textbook conversion, it also shows a real-world lumen figure that allows for light loss, estimates how many bulbs you need, and places your brightness on a visual lux scale with a to-scale, glowing room diagram — turning "how much light do I need?" into a clear shopping answer.

At a Glance

Lux to Lumens Calculator converts a target illuminance in lux into the lumens a room needs, from its area or length and width. It also adjusts for light loss and estimates how many bulbs to buy.

Lux to Lumens Calculator: features at a glance
Feature	What you get	Good for
Room size input	Enter length and width, or total area, in metric or imperial units.	Rooms measured in either square meters or square feet
Core conversion	Lumens equal lux multiplied by area in square meters, so 500 lux over 12 m² gives 6,000 lumens.	Quick lighting estimates for a known target
Light-loss factor	Set a utilization factor, such as 100% for the pure conversion or about 80% for a typical room, to get the lumens to install.	Allowing for walls, ceiling height and fixture losses
Bulb count	Enter lumens per bulb to get an approximate number of bulbs for the room.	Shopping for a room's worth of bulbs
Room presets	Recommended levels from 100 lux for hallways to 1,000 lux for fine work, based on EN 12464-1 and IES guidance.	Not knowing what lux level a room needs
Foot-candles and scale	Converts to foot-candles and places your value on a lux scale with a to-scale room diagram.	Comparing imperial and metric lighting figures

Lux to Lumens Formula

Lux is illuminance (light landing on a surface) and lumens is luminous flux (total light emitted). One lux equals one lumen spread over one square metre, so the conversion is simply lux multiplied by the lit area:

Core Conversion

$$\text{Lumens} = \text{Lux} \times \text{Area (m}^2\text{)}$$

Because real fixtures never deliver every lumen to the work surface — light is lost to walls, ceiling height, fixture design, and lamp ageing — the lumens you should actually install are higher. Dividing by a utilisation (light-loss) factor gives a practical target:

Real-World Lumens to Install

$$\text{Lumens to install} = \frac{\text{Lux} \times \text{Area}}{\text{Utilisation factor}}$$

Lux vs Lumens vs Foot-candles

Lumens tell you how much light a bulb produces in total. Lux tells you how bright a surface is once that light spreads out — the same bulb gives high lux in a small room and low lux in a large one. Foot-candles are the imperial version of lux: one foot-candle is one lumen per square foot, which equals about 10.764 lux.

How to Use This Calculator

Set the target lux: Type the illuminance you want, or pick a room type to load a recommended lux level automatically.
Enter the room size: Give the length and width, or switch to total area, in metres or feet.
Tune the lighting quality: Choose a utilisation factor (100% for the pure conversion, ~80% for a typical room) and the lumens per bulb you plan to use.
Click Calculate: Read off the total lumens, the real-world lumens to install, the bulb count, and a to-scale room diagram that brightens with your lux level.

Recommended Lux Levels by Room

These maintained illuminance targets follow common EN 12464-1 and IES lighting guidance. They are sensible starting points — adjust for personal preference, age, and task detail.

Lux to Lumens Calculator: Recommended Lux Levels by Room
Room / Task	Recommended Lux	Typical Use
Hallway / Stairs	100 lux	Safe movement, orientation
Bedroom	150 lux	Relaxed ambient light
Living Room	200 lux	General living, TV, chatting
Dining Room	200 lux	Meals and gatherings
Bathroom	300 lux	Grooming, mirror tasks
Garage / Workshop	300 lux	General DIY work
Classroom	400 lux	Reading and writing
Kitchen / Office	500 lux	Cooking, computer, task work
Retail / Supermarket	750 lux	Product display
Fine / Detailed Work	1,000 lux	Sewing, electronics, drafting

Worked Example

Suppose you want 500 lux in a 4 m × 3 m kitchen (12 m²). The core conversion is 500 × 12 = 6,000 lumens. Applying a typical 80% utilisation factor gives 6,000 ÷ 0.8 = 7,500 lumens to install. With 800-lumen LED bulbs, that is ⌈7,500 ÷ 800⌉ = 10 bulbs (or fewer, brighter fixtures).

What Affects How Many Lumens You Need?

📐 Room Size

Larger floor areas spread light thinner, so more lumens are needed to hold the same lux.

🎨 Surface Colours

Dark walls and floors absorb light; pale, matte surfaces reflect it and raise usable lux.

📏 Ceiling Height

Higher ceilings place fixtures further from the work plane, lowering the utilisation factor.

💡 Fixture Type

Diffusers, shades, and beam angle decide how much of each lumen reaches the surface.

⏳ Lamp Ageing

Bulbs dim over time and collect dust, so design with headroom via a maintenance factor.

🎯 Task Detail

Fine, close, or coloured tasks need more lux than casual ambient lighting.

Frequently Asked Questions

How do you convert lux to lumens?

Multiply the illuminance in lux by the lit area in square metres: Lumens = Lux × Area (m²). For example, 300 lux over a 20 m² room needs 300 × 20 = 6,000 lumens. If your area is in square feet, convert it to square metres first by multiplying by 0.0929.

What is the difference between lux and lumens?

Lumens measure the total amount of visible light a source emits, while lux measures how much of that light lands on a surface. One lux equals one lumen spread over one square metre. Spreading the same lumens over a larger area lowers the lux, so a bright bulb can still give dim lux in a big room.

How many lumens do I need for a room?

Multiply the recommended lux for the room by its area in square metres. Typical targets are about 150 lux for a bedroom, 200 lux for a living room, 300 lux for a bathroom, and 500 lux for a kitchen or office. A 12 m² kitchen at 500 lux needs roughly 6,000 lumens before allowing for light loss.

Why does this calculator show more lumens than lux times area?

Real rooms lose light to walls, ceiling height, fixture design, and lamp ageing. The utilisation factor divides the ideal lumens by this efficiency (typically about 80%) so you buy enough lumens to actually reach your target lux. Set the factor to 100% for the pure lux × area conversion.

How do I convert lux to foot-candles?

Divide the lux value by 10.764. One foot-candle equals one lumen per square foot, which is about 10.764 lux. For example, 500 lux is roughly 46 foot-candles.

Does bulb wattage matter for this calculation?

No. Only lumens matter for brightness. Wattage tells you energy use, not light output. A modern LED can produce 800 lumens from about 9 watts, while an old incandescent needs around 60 watts for the same 800 lumens. Enter lumens per bulb, not watts, to estimate how many bulbs you need.

Additional Resources

Reference this content, page, or tool as:

"Lux to Lumens Calculator" at https://MiniWebtool.com/lux-to-lumens-calculator/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: July 5, 2026

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