Now Reading
Lumens Calculator: How to Determine Total Required Lumens for Your Space

Lumens Calculator: How to Determine Total Required Lumens for Your Space

How much light is enough to light a room? Most designers and architects use two foundational principles of lighting design when planning and specifying lighting for any space:

  • the qualitative (or aesthetic) aspect of light 
  • the quantitative (or engineering) aspect of light

Calculating for total lighting required is considered quantitative.

The lumen method is the most commonly used for calculating the total light output needed for your space. With this formula, you first establish the intended use of the space, then you measure its square footage.

This guide will help you understand what the lumen method is and how to calculate it. You can also use the lumens calculator below to determine how many lumens you need based on room size and other key variables.

Table of contents:

  1. Helpful Lighting Terms
  2. The Lumen Method – How to Calculate Lumens
  3. Footcandle Requirements for Various Applications
  4. Summary: Calculating Total Lumens Needed for a Room
  5. Factoring in Lumen Lighting Variables
  6. Lumens Calculator
  7. Accounting for Personal Taste

Helpful Lighting Terms

Lumen

Lumen output is a measurement of the total quantity of visible light emitted by a light source. It’s also commonly known as brightness or light output.

The reference point: A standard 100-watt incandescent light bulb produces about 1,500-1,700 lumens. Strictly speaking, 600 LED lumens provides the same amount of light as 600 incandescent lumens. 

LED lights provide higher Color Rendering Index (CRI), so, while they more accurately reveal the colors of the subject being lighted, they don’t provide more light.

Wattage

Wattage is a measure of how much electricity (or energy) a light bulb consumes to achieve its lumen output.

Each type of light source — LED, fluorescent, halogen or incandescent bulbs — has a different lumen-to-watt ratio. If a 100-watt incandescent light produces 1,500 lumens, and a 10-watt LED light does the same, the 10-watt LED bulb may claim 100-watt equivalency and energy efficiency. 

Here’s a lumen-to-watt chart. Please note that these ratios may vary slightly, even between different  LED products.

Lumen-to-watt chart showing the conversion ratio of 800 lumens for 4 bulb types. LED 8-10W; CFL 13-14W; Regular incandescent 60W; Halogen 43W

Foot-candle

Foot-candle is the original measurement system for light intensity on a one square-foot surface from a uniform source of light. In other words, a foot-candle is the light measured one foot away from a candle.

Considering the human-centric principles of lighting design, the IES (the largest society of professional lighting designers) provides a footcandle chart on how many foot-candles of light humans need to perform tasks comfortably in different spaces.

For example, for washing dishes, they recommend that your lighting provides 20 foot-candles of light at two feet, six inches off the floor. This is also referred to as the horizontal target.

The Lumen Method – How to Calculate Total Lumens Needed

  1. Determine room size by square footage. Multiply the length times the width of the room to get the room square footage. For example, if the room is 10 feet wide and 10 feet long, the room square footage will be 100 square feet.
  2. Establish the footcandle requirement for your application. Lighting requirements vary depending on the type of room being lit, also known as the application. For example, a bathroom or kitchen will require more foot candles than a living room or bedroom. Once you establish the intended use of your space, browse this footcandle chart for the IES-recommended footcandle requirement for your application.
  3. Multiply the room square footage by the footcandle requirement. For example, a 100 square-foot living room, which needs 20 foot-candles, will need 2,000 lumens. A 100 square-foot dining room, which needs 40 foot-candles, will require 4,000 lumens.
Graphic that compares total lumen output in a living room to a dining room with 3 lamps (220 lumens each) and a ceiling fan with a ceiling light in a dining room
Graphic showing the preferred LED lighting layout. LED lights placed towards the center of the room are more efficient than lights placed in the corners

We’ve created a helpful guide to How Many Lumens You Need that walks you through this calculation in more detail.

Footcandle Requirements for Various Applications

Commercial Lighting Footcandle Requirements

RoomFoot-candles Needed
Offices: Average Reading and Writing50-75
Offices: Hallways10-20
Offices: Rooms with Computers20-50
Auditoriums / Assembly15-30
Hospitals: General Areas10-15
Hospitals: Labs / Treatment Rooms75-100
Libraries50-100
Schools30-100

Residential Lighting Footcandle Requirements

RoomFoot-candles Needed
Living Room10-20
Kitchen: General30-40
Kitchen: Stove70-80
Kitchen: Sink70-80
Dining Room30-40
Bedroom10-20
Hallway5-10
Bathroom70-80

Summary: Calculating Total Lumens Needed for a Room

Let’s recap how to gauge how much light you need for a space. Multiply your room square footage by the footcandle requirement. For example, a 100-square foot living room, which needs 20 foot candles, will need 2,000 lumens. A 100-square foot dining room, which needs 40 foot-candles, will need 4,000 lumens.

Factoring in Lumen Lighting Variables

Ceiling Height Variable

Note: Only read this section if your ceiling height is taller than 10ft. If your ceiling height is below 10ft, the Lumen Method above and the lumens calculator below will be sufficient for determining the required light output for your application.

If you have high ceilings in a space, then you must account for that in your lumens calculation. You do that with a footcandle multiplier.

To calculate for your recommended footcandle multiplier, use the following formulas:

footcandles (fc) = cd ÷ h

cd = candlepower

h = distance between the lamp and the horizontal target

Once you determine your desired footcandle level, you multiply that by your room square footage.

See Also

Wall Color Variable

If you have especially dark colored walls and furniture or if you’re using light fixtures with shades, you’ll need roughly an additional 10 lumens per square-foot.

Lumens to Candlepower Conversion

Candlepower is a unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents. 

The historical candlepower is equal to 1.02 candelas. In modern usage, candlepower is sometimes used as a synonym for candela.

Lumen output = C/0.07958

For example, 200 candlepower would equal: L = 200 candlepower / 0.07958

Do the division using a calculator: 200 candlepower / 0.07958 = 2,513 lumens

Lumens Calculator

This free calculator can help you calculate  the lumens needed to light a room. You can then shop for lighting that adds up to the total lumens you need.

Please note that the calculator assumes a standard 8-foot ceiling. It then uses averages and recommended light levels to calculate for different ceiling heights. Also note that these are estimations.  For exact analysis, please consult a lighting design professional.

LUMEN/WATT CALCULATOR

Measurement Unit



Illumination Intensity
Wall Color
Light Placement

Accounting for Personal Taste

Personal preference will play a large role  in determining how much light you need in a space. If you like the room to be especially bright, you may want to add an additional 10-20% to our numbers and then install dimmers to adjust the light to desired levels.

When lighting is properly designed in a space, you notice the room and the objects in it. In other words, you notice what the lighting illuminates, not the lighting products themselves. Bad or deficient lighting design shows up as hot spots, dark spots and unintentional shadows.

Good or efficient lighting design accounts for total general and task lighting required for a space. Dynamic or superior lighting design factors the qualitative, human experience. It lights for vertical (not merely horizontal) visual impressions, such as walls — as well as ceilings with uplighting to minimize shadows and dark spots for smooth, streamlined and evenly distributed light.

0 0 votes
Article Rating

Comments

Subscribe
Notify of

52 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
kenandsue.mcintyre@gmail.com'
Sue
2 years ago

I saw some lights with 60 watt bulb capacity and want a well lit dining room. Would three pendant lights work or would 4 be better for a space with no outside light coming in?

kenandsue.mcintyre@gmail.com'
Sue
2 years ago
Reply to  David P Hakimi

It is basically 9×15 with a jut out on one end of the room. It is an interior room with NO windows. The ceiling is 9 ft high and no paint color has been decided on yet.

turkeysneck@hotmail.com'
Edward
2 years ago

I’m not sure if the manual calculation or the calculator is incorrect, but when I compare results, they differ. I checked and recheck so I don’t know which result to believe!

turkeysneck@hotmail.com'
Edward
2 years ago
Reply to  David P Hakimi

I have looked at my figures again and I realise where I was going wrong; I was converting from m sq to ft sq using an incorrect calculation.

Now that I’ve corrected, there’s not so much of a difference between the calculator and my workings out!

Thanks
Edward

arnoldjami07@gmail.com'
Jami
2 years ago

In a roughly 20×20 office space we have 6 2×2 flush led ceiling lights. They are 4,000 lumens. Is this too much?

otooles_pub@yahoo.com'
Jennifer
2 years ago

I am finding your answers to others thoughtful and beneficial so I decided to throw my questions out there. We were at a store today looking at lighting and I found myself getting quickly overwhelmed. We are building our house and are just beginning the wiring phase and no light… Read more »

drgassnermm@hotmail.com'
Doug
2 years ago

Hi there,I have a 13 x18 kitchen with 1 window,light colored walls and 8′ ceilings
Want to use led lighting,os 5200 lumens good?

jimmy_van@verizon.net'
JAMES F VAN DOVER
2 years ago

I have a shop that is 16 x 32 x 14 high I bought 8 2×2 4 tube led lights which are 5000 lumens each I believe 4000k. I plan on hanging them in 2 straight lines, in each line they will be @ 4 foot apart and @ 8… Read more »

john2beach@gmail.com'
How much LED lights would I need for a 25 foot fla
2 years ago

How much LED light would I need for a 25 foot flagpole

amylsutton@gmail.com'
Amy
2 years ago

Is 2300 lumens enough light to properly illuminate a 12 x 15 foyer with 16 foot ceiling?

amylsutton@gmail.com'
Amy
2 years ago
Reply to  David P Hakimi

Many thanks!

mearyaeldabaa@hotmail.com'
Mary
2 years ago

Wow! Thank you so so much I really needed to read this and know more. Also I have a question if you can help, so you know the deference between the led light and the grow light for plants? Can I use the normal led let ( with high Lumen)… Read more »

jonton@gmail.com'
John
2 years ago

Great.

author@scottmcgaugh.com'
Scott
2 years ago

Perhaps I missed it, but if a measured kitchen space needs 4000 lumens and has 6 recessed ceiling lights, do you divide 4000 by 6 to get a per-fixture lumen level ? Or buy 6, 4000 lumen recessed (retrofit) fixtures (with dimmer?)? Thank you in advance.

EDHarden@juno.com'
Elizabeth
2 years ago

Thank you for this helpful article. There is a diagram at the end entitled “Preferred LED Lighting Layout” that suggests LED lights should not be placed in corners. Does this apply to any type of LED lights or only to downlights?

Petersundstrom@outlook.com'
Peter
2 years ago

Wow. Consise factual and easy to understand. Plus imbedded calculator.
Good job

tfbjr25@hotmail.com'
Timothy Brady
2 years ago

This is great information. My wife and I are struggling right now trying to get the right lighting in a home we bought. We just recently had installed 4x LED can lights but we are unsure of the Lumens but are pretty certain it is not enough. Our estimation is… Read more »

kathidancer@aol.com'
Kathi
2 years ago

I have a 3200 sq ft large party room (an almost square space) with 10-12 ft ceilings (slight vault). I’d like to do recessed downlights as the main source of light. The walls are a light color. If my fixtures each provide 1200 lumens, how many fixtures will I need?… Read more »

kathidancer@aol.com'
Kathi
2 years ago
Reply to  David P Hakimi

thanks- that helps 🙂

alice.sims.gunzenhauser@gmail.com'
Alice
2 years ago

Thanks very much for this resource! I am trying to light a basement art studio that has no natural light. It’s about 14′ x 20′; the ceiling is between 6′ and 7′, depending whether one measures from the top or bottom of the beams across it. Your calculator says I… Read more »

alice.sims.gunzenhauser@gmail.com'
Alice
2 years ago
Reply to  David P Hakimi

Thanks again. I really appreciate it.

annmcrisp@gmail.com'
Ann
2 years ago

What kind of lighting is best for overhead tube light in kitchen….Cool, Warm, Bright? is 4000K too bright?

dkerr6@gmail.com'
Duane Kerr
2 years ago

Hello,
If I want to install in-ground well lights (2) to shine up at a 5′ x 8′ flag on a 35 foot pole, how many lumens should each light fixture be?

rixhardjohncarolino@gmail.com'
Richard
2 years ago

Hi,

I understand this is rough estimate as there are other factors. My question is, if I determined my needed lumens on the entire room, should I divide it to number of fixtures/downlights?

gannonguckert@yahoo.com'
J. Guckert
2 years ago

What a wonderfully well-written, informative piece. I’m a picky, writer-type, from the technical and non-fiction arenas, and I love finding such good writing scattered around the web, in non-obvious places.

nepalibabu2000@gmail.com'
Shiva Shrestha
1 year ago

Nice explanation

s.diamond@hotmail.co.uk'
Susan
1 year ago

So enjoyed your article on ‘How to Determine how many Lumens you’ll need to properly light your space’. So clear, so brilliantly explained…..at least 100,000 lumens worth!

virgilio.vilela@gmail.com'
Virgílio
1 year ago

Thank you for such crystal clear text and the usefull tool available that allow us to do quick calculations.

paul71k@yahoo.com'
Paul
1 year ago

I found this article while researching about IES profiles for a game developer. We have the ability to use IES profiles for each light source in our development tools, but I needed to find a good source on how much lighting to use in each “room” to help narrow down… Read more »

terry108@sbcglobal.net'
Terry B
1 year ago

Hi David, This is such a helpful and well-written blog entry. Perhaps you can offer me a suggestion. I am looking for a lamp for a bedside table, specifically to have enough light to be able to do light reading or paperwork (eg, paying bills) before going to sleep. I… Read more »

pub934@yahoo.com'
Paul
1 year ago

I just wanted to say what an absolute gem of a website you have here. I live abroad and am not able to purchase from yourselves, but just wanted to say thank you for such as awesome blog and help.

no@email.com'
Sam
1 year ago

Hi, you should check the calculator on this page – the output for meters compared to feet is way off.

johnmchardy@rogers.com'
John McHardy
1 year ago

First let me say how grateful I a that I found this blog – your explanation of how to determine the total amount of light required for a rec room I am building was easy to understand and has moved me significantly closer to understanding how many led pot light… Read more »

johnmchardy@rogers.com'
John McHardy
1 year ago
Reply to  David P Hakimi

David Thank you for the prompt replies as I expect you are a rather busy person ! I think I understand what you are saying about beam spread….. if a 600 lumen down facing ceiling led light fixture has a 45 degree beam spread then the light circle diameter would… Read more »