Lighting Calculator
Calculate the perfect lighting for any room. Get required lumens, recommended lux levels, and bulb count based on room size and type. Free lighting calculator.
About This Calculator
What Is the Lighting Calculator?
The Lighting Calculator helps you determine the optimal illumination for any room in your home or office. Whether you are designing lighting for a new kitchen, upgrading your living room, or setting up a home office, this tool calculates the exact lumens required based on room dimensions and internationally recognized IESNA (Illuminating Engineering Society of North America) recommended illuminance standards.
Simply select your room type, enter the length and width in meters or feet, and choose a bulb type to instantly see how many fixtures you need. The calculator supports both metric (lux per square meter) and imperial (foot-candles) units, making it useful for users worldwide.
How the Calculation Works
The formula is straightforward: Required Lumens = Recommended Lux × Room Area (m²). For imperial units, we convert square feet to square meters first. The recommended lux values come from IESNA lighting guidelines, which specify different illuminance levels for different activities — kitchen counters need high task lighting (538 lux), while bedrooms work well with softer ambient light (108 lux).
Once we know the total lumens needed, the calculator divides by your chosen bulb's lumen output to determine the number of bulbs required. A breakdown table shows alternative bulb options so you can compare costs and fixture counts.
Regional Notes
United States: Lighting is typically measured in foot-candles (fc). One foot-candle equals 10.764 lux. Common residential recommendations: living rooms 10-20 fc, kitchens 30-50 fc, bedrooms 10-20 fc, bathrooms 20-50 fc. Use the imperial unit toggle to work in feet.
United Kingdom: UK building regulations (Part L and BS 8206) recommend 150-300 lux for general living areas and 300-500 lux for kitchens and work surfaces. Use the metric unit toggle for meters. Energy-efficient LED lighting is encouraged through building regulations.
India: The National Building Code (NBC 2016) recommends 150-200 lux for living rooms, 200-300 lux for kitchens, and 300-500 lux for study areas. With India's tropical climate, consider LED lighting to minimize heat generation and reduce air conditioning load.
Frequently Asked Questions
How many lumens per square foot do I need?
The recommended lumens vary by room type: living rooms need about 15 foot-candles (161 lux), kitchens need 30-50 foot-candles (323-538 lux), and bedrooms need 10-40 foot-candles (108-430 lux) depending on the activity. Multiply the recommended foot-candle value by your room area in square feet to get total lumens needed.
What is the difference between lumens and lux?
Lumens measure the total amount of visible light emitted by a source. Lux measures how much of that light illuminates a surface. One lux equals one lumen per square meter. A 800-lumen bulb emits 800 lumens total, but the lux value at a surface depends on distance and spread. Our calculator uses lux to determine how much light your room needs based on its size.
How do I calculate lighting for a room?
To calculate room lighting: 1) Measure your room length and width, 2) Multiply to get area, 3) Look up the recommended lux for your room type (e.g., kitchen counter needs 538 lux), 4) Multiply lux by area in square meters to get required lumens, 5) Divide by your bulb lumen rating to get number of bulbs needed.
What is the best lighting for a bedroom?
Bedrooms need layered lighting: ambient lighting at 108 lux (10 fc) for general use, reading lighting at 430 lux (40 fc) near the bed or chair, and dressing table lighting at 430 lux (40 fc). Use dimmable fixtures, separate switches for overhead and task lighting, and consider warm color temperatures (2700-3000K) for a relaxing atmosphere.
How many LED bulbs do I need for a kitchen?
A 10 square meter (108 sq ft) kitchen needs approximately 3,230 lumens for ambient lighting and 5,380 lumens for task areas. With standard 800-lumen LED bulbs, you would need 4 bulbs for ambient lighting and 7 bulbs for task lighting over the counter. Consider using 1100-lumen or 1600-lumen bulbs to reduce fixture count.
What is the recommended illuminance for an office?
Home offices and desk areas need 430 lux (40 foot-candles) for comfortable computer work and reading. In the US, OSHA recommends 30-50 foot-candles for general office work. In the UK, HSE guidelines suggest 300-500 lux for general office tasks. Position task lighting to avoid screen glare and use adjustable desk lamps for focused work.
Can I use too many lumens in a room?
Yes, over-illuminating a room causes glare, eye strain, and wasted energy. Stick to recommended lux ranges: 108-215 lux for relaxed areas like bedrooms and hallways, 323-538 lux for task-oriented spaces like kitchens and offices. Use dimmers and multiple light zones to adjust brightness for different activities and times of day.
How does room color affect lighting needs?
Room color significantly impacts how light reflects: white walls reflect up to 80% of light, while dark walls absorb 80-90%. Dark-colored rooms may need 2-3 times more lumens than light-colored rooms of the same size. Our calculator uses standard IESNA recommendations for neutral-colored rooms; adjust by adding 30-50% for dark rooms.