How Many Lumens Per Square Foot Do You Really Need? A Practical Guide

Planning the right lighting for a room—or even a specific work area—starts with one key question: How bright should the space be? Whether you're setting up a cozy bedroom or installing task lighting over a kitchen counter, understanding lumens, lux, and foot-candles will help you get it right the first time.

Below is a simple, step-by-step guide that walks you through the entire process.

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1. Start With the Type of Space and Activity

Every space performs differently, and so should its lighting.

A bedroom needs soft, low-intensity light to help you wind down.
A kitchen counter used for food prep needs much stronger task lighting.
A workshop or craft table requires even higher brightness for precision work.

Lighting standards usually express brightness in lux or foot-candles—units that measure how much light reaches a surface. A lighting calculator can help you select the recommended brightness level for each type of room or task.

2. Determine the Area You’re Lighting

Next, figure out the size of the area you want to illuminate.

For a full room (like a bathroom or bedroom), this is just the room’s length × width.
For a specific zone—like a kitchen island, workspace, or tabletop—measure only that surface.

Example:
A counter that’s 4 meters long and 0.6 meters wide has an illuminated area of:
4 × 0.6 = 2.4 m²

3. Calculate How Many Lumens You Need

Once you know:

the recommended brightness (lux or foot-candles), and
the area (m² or ft²),

You can calculate the required lumens using the formula:

Lumens = Illumination Level × Area

If your lighting standard is in foot-candles, remember:
1 foot-candle = 10.764 lux

This formula tells you how much total light output is needed to properly illuminate the space.

4. Convert Lumens Into Number of Bulbs

After determining the lumens required, choose a bulb type and check how many lumens each bulb produces. LED bulbs typically have much higher efficiency than old incandescent bulbs, so wattage is no longer a reliable indicator of brightness.

Use:

Number of bulbs = Total lumens required ÷ Lumens per bulb

Round up to the nearest whole number.

5. Example: Lighting a Kitchen + Countertop

Let's walk through a real example.

Step 1: Recommended brightness

Kitchen ambient lighting: approx. 108 lux
Kitchen counter (task lighting): approx. 538 lux

Step 2: Calculate area

Full kitchen: 4 m × 2.5 m = 10 m²
Countertop: 4 m × 0.6 m = 2.4 m²

Step 3: Determine lumens

Kitchen: 108 × 10 = 1080 lumens
Countertop: 538 × 2.4 = 1291 lumens

Step 4: Choose your bulbs

Overhead bulbs: 800 lumens each → 1080 ÷ 800 ≈ 2 bulbs
Counter LED spots: 200 lumens each → 1291 ÷ 200 ≈ 7 bulbs

So you’d need:

2 overhead bulbs for the kitchen
7 small LED task lights for the counter

FAQs

How do I calculate lighting for any room?

Measure the space (length × width)
Find the recommended brightness in lux or foot-candles
Use lumens = lux × area
Divide by the bulb’s lumen output

How many lumens do I need for a 4 m × 5 m studio?

A 4×5 m studio = 20 m².
Recommended lighting: ~323 lux
Calculation: 323 × 20 ≈ 6460 lumens
With 1600-lumen bulbs, you’d need 5 bulbs.

What’s the best lighting level for a bedroom?

Different activities need different brightness:

Relaxing / preparing for sleep: ~50 lux
Reading: ~400+ lux
Detailed tasks: up to ~540 lux

You can combine multiple bulbs or fixtures to achieve layered lighting.

Lumen vs. Lux — What’s the difference?

Lumens: total light output from a source
Lux: how much of that light actually lands on a surface

They’re linked by:
Lumens = Lux × Area