Lighting Calculator

How Much Light Does a Room Need?

Good lighting depends on room type, activity, and area size. Our Lighting Calculator estimates required lumens from room dimensions and recommended illumination levels, then tells you how many bulbs you need.

The Lighting Formula

Required lumens equal illumination level times area:

$$Lumens = Lux \times Area$$

Lux measures light falling on a surface. A kitchen counter for detailed tasks needs more lux than a bedroom used for relaxing. Once you know total lumens, divide by each bulb's lumen output and round up.

$$Bulbs\ Needed = \lceil \frac{Lumens}{Bulb\ Lumens} \rceil$$

Room Illumination Guidelines

• Bedroom ambient: around 54 lux for soft evening light
• Living room: around 108 lux for general use
• Kitchen task areas: around 538 lux for food prep
• Desk or sewing: around 538 lux for detailed work

Pair this tool with our Electricity Cost Calculator to estimate how much your lighting setup will cost to run.