Lighting Calculator
Calculate the total lumens, number of fixtures, wattage, and annual energy cost for any room. Enter your room dimensions, room type, and lighting preferences for accurate results.
How the lighting calculator works
This calculator determines the total lumens required to adequately light a room based on its area and the recommended illuminance (lux) for the room type. It then calculates the number of fixtures needed, the total wattage, and the annual energy cost based on your electricity rate and daily usage.
Enter your room length, width, room type, and lighting preferences below. The calculator instantly shows your recommended lighting setup, including a comparison of different bulb types and a breakdown of the calculations.
Step 1: Room Information
Recommended Illuminance (Lux)
Kitchens typically require 300–500 lux for task lighting. The calculator uses the mid-range value for your selected room type.
Step 2: Lighting Preferences
Energy Efficiency Tips
LED bulbs use up to 90% less energy than incandescent bulbs and last 15–25 times longer. Switching to LED can save you £100+ per year on energy bills.
Lighting Results
Total Lumens Required
Bulb Type Comparison
| Bulb Type | Efficacy (lm/W) | Total Wattage | Fixtures Needed | Annual Cost | CO₂ (kg/year) |
|---|
Lighting Breakdown
Calculation Formula
Total Lumens = Area × Illuminance (Lux)
Fixtures Required = Total Lumens ÷ Lumens per Fixture · Total Power = Fixtures × Wattage per Fixture · Annual Cost = (Total Power × Hours/Day × 365 × Cost/kWh) ÷ 1000
Frequently Asked Questions
How many lumens do I need per square metre?
The required lumens per square metre (lux) depends on the room type. Living rooms typically need 150–300 lux, kitchens 300–500 lux, and offices 300–500 lux. Use our calculator to get precise recommendations for your space.
What is the difference between lumens and lux?
Lumens measure the total light output from a source. Lux measures how much light reaches a surface (lumens per square metre). Lux = Lumens ÷ Area (m²).
How many LED lights do I need for a room?
Divide the total lumens required for the room by the lumens per fixture. For example, if a room needs 3,000 lumens and each LED bulb provides 800 lumens, you’ll need 4 bulbs.
What is the recommended illuminance for different rooms?
Living rooms: 150–300 lux, Bedrooms: 100–200 lux, Kitchens: 300–500 lux, Bathrooms: 200–300 lux, Offices: 300–500 lux, Garages: 100–200 lux, Hallways: 100–150 lux, Dining rooms: 150–300 lux.
How do I calculate the annual energy cost of my lighting?
Multiply total wattage by hours used per day, then by 365 days, divide by 1,000 to get kWh, and multiply by your electricity cost per kWh. The calculator does this for you automatically.
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