How to Calculate LED Power for Each Room in Your Home

Introduction

Choosing the right LED lighting for each room can seem complicated, but with a simple formula, you can calculate the exact wattage needed – and avoid rooms that are too dark or excessively lit.

In this guide, we explain the step-by-step method, both for individuals renovating their homes and for electricians and designers who need to precisely size installations.

The Basic Concept: Lumens, Not Watts

The most common mistake is choosing LED bulbs by their wattage. With LED, what matters is the lumens (lm) — the amount of light emitted.

• A 60W incandescent bulb emits about 800lm
• An 8-9W LED bulb emits the same 800lm

Therefore, the starting point is always to calculate how many lumens you need – and only then choose the product.

The Formula: Lumens per Square Metre

The general rule is simple:

Required lumens = Room area (m²) × Recommended illuminance level (lux)

The illuminance level (in lux) varies depending on the room's use:

Practical Example

Imagine a kitchen with 12 m² and a recommended level of 400 lux:

• Required lumens = 12 × 400 = 4,800 lm
• If you use 1,200lm LED downlights, you need 4 downlights

It's that simple!

Utilisation Factor and Losses

In practice, not all light reaches the work plane. We recommend applying a correction factor of 1.25 to compensate for losses due to reflection, wall colour, and ceiling height:

Real required lumens = Area × Lux × 1.25

For the same kitchen: 12 × 400 × 1.25 = 6,000 lm → 5 downlights of 1,200lm.

Ceiling Height Matters

For ceilings above 3 metres (warehouses, industrial spaces), light disperses more. In these cases, use high-power LED high bay lights (100W–200W) with narrow beam angles (60°–90°) to concentrate light on the work area.

Final Tips

• Dark walls absorb more light — increase lumens by 20%
• Dimmable lights allow you to adapt the intensity to the time of day
• Colour temperature: use 3000K (warm) for resting areas and 4000K–6000K (cool/neutral) for work and kitchen
• Combine general lighting with accent lighting for a more professional result

Conclusion

Calculating the right LED wattage is not difficult – just know the area, the room's use, and apply the formula. With the right products and correct sizing, you save energy and ensure visual comfort throughout your home or commercial space.

Explore our range of downlights, LED tubes, and industrial high bays and find the ideal solution for your project.