Lighting · room brightness
Lumens needed per room calculator.
Pick the room type and enter its length and width. The calculator multiplies the floor area by the recommended footcandle range (footcandles are lumens per square foot) to give the total lumens you need from all fixtures, plus the lux equivalent. Feet or metres. Runs in your browser; nothing is sent or stored.
Room
Lumens needed
Worked example
A 14 x 12 ft bedroom is 168 sq ft. The bedroom range is 20 to 50 footcandles, so 168 x 20 = 3,360 to 168 x 50 = 8,400 lumens, which is 215 to 538 lux (1 footcandle = 10.76391 lux). With a 10 ft ceiling and the adjustment on, multiply by 10 / 8 = 1.25 for 4,200 to 10,500 lumens. A 120 sq ft kitchen sized for preparing and cooking (50 to 100 fc) needs 6,000 to 12,000 lumens.
Method
Plain arithmetic. Total lumens = floor area in square feet x recommended footcandles. A footcandle is one lumen per square foot, so the product is the lumens that need to land on the floor area. Lux = footcandles x 10.76391 (NIST), and metric area is converted with 1 ft = 0.3048 m. The optional adjustment multiplies by ceiling height / 8 ft when the ceiling is higher than 8 ft, which is our reading of the LEDYi note that levels are for 8 ft ceilings and should rise proportionally.
Limits. The footcandle ranges are as listed by Super Bright LEDs and LEDYi from Illuminating Engineering Society guidance; check the IES for design work. This is a simple room-average method: it ignores fixture losses, wall colour, furniture and task lighting placement. Use the lumens printed on each bulb or fixture and add them up; do not use watts.
Rule of thumb, not a standard. These are design rules of thumb from published decorating guides, not building codes or standards. Treat the result as a starting point and tape it out in the room before you buy or drill. Results are shown in both imperial and metric. Conversions use 1 in = 2.54 cm and 1 ft = 0.3048 m.
Sources, each opened 2026-10-08:
- Home Lighting Guide: IES Residential Recommended Lighting Levels (Super Bright LEDs, citing the IES): footcandle ranges by room and lumens = area x footcandles.
- Residential Recommended Lighting Levels (LEDYi Lighting, updated 16 Mar 2026): same formula and a note that levels assume 8 ft ceilings.
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically (NIST): lists 1 inch = 2.54 cm, 1 foot = 0.3048 m and 1 footcandle = 10.76391 lux.
Frequently asked questions
How many lumens do I need for a room?
Multiply the floor area in square feet by the recommended footcandles for the room. Super Bright LEDs lists 10 to 20 for a living room, 20 to 50 for bedrooms and bathrooms, 20 to 50 for general kitchen light and 50 to 100 for preparing and cooking. A 168 sq ft bedroom therefore needs about 3,360 to 8,400 lumens.
What is a footcandle?
Super Bright LEDs describes a footcandle as one lumen per square foot and lux as one lumen per square metre. NIST lists 1 footcandle as 10.76391 lux, which the calculator uses for the lux range.
Why is the range so wide?
The recommended level depends on the task and on preference. A hallway is 5 to 10 footcandles while a kitchen counter or a reading room is 50 to 100. Start near the low end for relaxed rooms and the high end for detailed tasks, and use dimmers.
Does ceiling height matter?
LEDYi says the listed levels are for 8 ft ceilings and that higher ceilings need more lumens in proportion. The adjustment is optional and multiplies the result by ceiling height / 8 ft.
Is this per bulb or for the whole room?
It is the total across all fixtures in the room. Add up the lumens printed on the packaging of the bulbs or fixtures you plan to use and compare the total with the range.