Lighting (Lumen) Calculator
Enter the room type and area to see the lumens you need and LED bulb options.
This calculation gives estimates from fixed lux ranges for each room type. Ceiling height, surface colour and fixture type can change the result; for important projects, consult a lighting designer.
How to Calculate Lighting Requirements by Square Metre
The basic formula: Area (m²) × Target lumen/m² = Required total lumens. Example: the calculator uses a 300–500 lux range for a kitchen, so a 15 m² kitchen needs 4,500–7,500 lm. Bulbs are sized from the middle of the range: 15 × 400 = 6,000 lm. You can get this from one large bulb or several medium-power LEDs. The tool does this calculation and lists bulb options.
What Is the Difference Between Watt and Lumen?
Watt is the amount of energy the bulb uses, and it drives your electricity bill. Lumen is the amount of light the bulb gives off, and it shows actual brightness. In the incandescent era, 60 W = 800 lm was a fixed reference. In the LED age, 8–10 W can produce 800 lm, so wattage is no longer an indicator of brightness. When choosing a bulb, look at the lumen value on the packaging, not the wattage.
Recommended Lumen Values by Room
The ranges below are the values the calculator uses (1 lux = 1 lm/m²). Bulb suggestions are based on the middle value in brackets. A standard ceiling height (2.5–2.7 m) and mid-tone surfaces are assumed.
| Room Type | Target Lumen/m² | Purpose |
|---|---|---|
| Living Room | 100–300 lm/m² (200) | Comfortable reading and social activity |
| Kitchen | 300–500 lm/m² (400) | High visibility for cutting and cooking |
| Bedroom | 100–200 lm/m² (150) | Calm, low light |
| Study / Office | 500–750 lm/m² (625) | Extended screen or paperwork sessions |
| Bathroom | 250–500 lm/m² (375) | Safe movement and personal care |
| Hallway / Corridor | 80–150 lm/m² (115) | Enough to find your way through a passage |
| Garage | 150–300 lm/m² (225) | Vehicle maintenance and safety |
How to Choose LED Bulbs
Once you know the total lumens you need, split them across several medium-power bulbs rather than one powerful bulb where you can. The light spreads more evenly, with fewer shadows.
Colour Temperature (Kelvin) Selection
2700–3000 K
Warm White
Living room, bedroom
4000 K
Neutral White
Kitchen, bathroom
5000–6500 K
Cool White
Study, garage
CRI (Colour Rendering Index)
CRI measures how accurately a bulb renders the true colours of objects (scale 0–100). CRI ≥ 80 is sufficient for everyday use. For colour-sensitive areas such as makeup mirrors, workshops or galleries, choose CRI ≥ 90.
Key Considerations in Lighting Design
- Ceiling height: Increase lumen requirements by 20–30% for ceilings above 3 metres; light weakens by spreading before reaching surfaces.
- Surface colour: Dark walls and floors absorb light; light-coloured surfaces allow the same comfort with fewer bulbs.
- Task lighting: Add task lighting to work desks and kitchen counters in addition to general lighting; it reduces eye strain.
- Dimmer: Dimming dimmer-compatible LED bulbs in the evening saves energy and supports your circadian rhythm.
- Light distribution: Several medium-power bulbs instead of one powerful bulb reduce shadowy spots. Spotlights, panels and pendant fixtures have different beam angles; plan placement accordingly.