How many lumens do I need per square foot?

A general rule of thumb is 20 lumens per square foot for ambient lighting, but task areas like kitchens or desks may require 50 lumens or more per square foot depending on the activity.

Can I use this calculator to pick LED bulbs?

Yes — if you know the total lumens needed for your room, you can compare that to the lumen output listed on LED bulb packaging to find a matching replacement.

What is the difference between foot-candles and lux?

Foot-candles and lux both measure illuminance; one foot-candle equals approximately 10.764 lux, so lux is the metric version of the same measurement.

Do I need to account for ceiling height in the calculator?

Higher ceilings spread light over a larger area, so you may need more bulbs or higher-output bulbs to maintain the same brightness on the floor or work surface.

Is the bulb count from Omni Calculator exact?

It provides an estimate based on the inputs you give; actual needs can vary with wall color, furniture, and how light reflects around the room.

Home & Household2 options compared

Lighting Calculator

Calculates the number of light bulbs needed for optimal illumination in a space based on factors such as room size, height, and desired brightness level. Users input measurements and preferences, and the calculator provides an estimated bulb count to ensure adequate lighting without waste. Ideal for homeowners, decorators, and anyone planning interior spaces looking to enhance visibility and...

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Editors’ Top PickBased on community votes

Number Convert

numberconvert.com

Convert light and illumination units with this free lighting calculator. Essential for photography and lighting design.

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Omni Calculator
omnicalculator.com
This lighting calculator determines how many light bulbs you need to illuminate a particular space.
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Side by side

Lighting Calculator options compared

Tool	Best for	Strengths	Limitations
Number Convert numberconvert.com	Converting lumen/watt units	Converts between lumens, lux, candela Professional lighting design use	Does not calculate bulb count for a room No input for ceiling height or square footage
Omni Calculator omnicalculator.com	Estimating bulb count for a room	Takes room dimensions and ceiling height Selectable lighting types (kitchen, bedroom, etc.)	Fewer unit conversion options than Number Convert

Buyer's guide

How to choose a lighting calculator

When you need to light a room from scratch, start with the dimensions and the kind of space you are illuminating — a kitchen needs more light than a bedroom. If you already know the total lumens your bulbs produce, use that number to compare wattage or check compatibility with your fixtures. The difference that matters is whether you are designing a new layout (Omni) or converting existing specs (Number Convert).

Questions

Lighting Calculator FAQ

How many lumens do I need per square foot?: A general rule of thumb is 20 lumens per square foot for ambient lighting, but task areas like kitchens or desks may require 50 lumens or more per square foot depending on the activity.
Can I use this calculator to pick LED bulbs?: Yes — if you know the total lumens needed for your room, you can compare that to the lumen output listed on LED bulb packaging to find a matching replacement.
What is the difference between foot-candles and lux?: Foot-candles and lux both measure illuminance; one foot-candle equals approximately 10.764 lux, so lux is the metric version of the same measurement.
Do I need to account for ceiling height in the calculator?: Higher ceilings spread light over a larger area, so you may need more bulbs or higher-output bulbs to maintain the same brightness on the floor or work surface.
Is the bulb count from Omni Calculator exact?: It provides an estimate based on the inputs you give; actual needs can vary with wall color, furniture, and how light reflects around the room.

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