How Much Light is Needed in a Room?

Here’s an interior design question that I commonly get asked; “How much light is needed in a room?” The answer typically surprises people so I thought I’d give a little overview to help understand what needs to be considered when lighting a space.  Ever notice the light in a perfectly lit room? Probably not. Nobody ever complains when they can see everything perfectly.  On the other hand, when a space is poorly lit, we're frustrated by the lack of light and our inability to perform tasks effectively.

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Before we dive in let’s talk about the three types of lighting; general (or ambient if you want to be fancy), task and decorative/accent lighting.  As you might guess, each type of lighting has its own function.  Here’s a brief guide to help you out.

GENERAL LIGHTING
General lighting is the base lighting that is needed in a space to be able to see in the dark hours of each day.  Its sole purpose is to generally illuminate a space.

TASK LIGHTING
Task lighting states its function right in the name; its purpose is to light areas where tasks will be performed.  Typically this type of lighting is in close range of task areas, for example under cabinet lighting in the kitchen to assist with food preparation or table or floor lamps placed closely to seating to help with reading.

DECORATIVE/ACCENT  LIGHTING
This type of lighting is my favourite.  It can have an enormous impact on a space in terms of interior design.  Decorative and/or accent lighting is lighting that creates a mood, highlights specific areas such as artwork or serves as a focal point to add drama to a space.

In good interior design, the three lighting types work together to ensure a room is as functional as it is beautiful.

SO HOW MUCH LIGHTING IS NEEDED TO LIGHT A ROOM?
Before I answer that question, let me educate you on a few lighting terms. Forgive me if I am oversimplifying things, I’m just trying to be as clear as possible for anyone out there who doesn’t know this stuff.

WATT
In terms of lighting, a Watt refers to the amount of energy it takes to produce a certain amount of light. Thus, the higher the wattage value, the more energy it takes to light a space. 

LUMEN
Lumens refer to the amount of brightness a light emits.  Therefore, the greater the lumen count, the brighter a room will be. 

KELVIN
A Kelvin is a measurement of the colour temperature of a light in degrees. Stay with me here because Kelvin measurements are a little counterintuitive. The higher the temperature of a light source, the cooler the light will appear. Consequently, high Kelvin values represent cool (bluish) light temperatures and low Kelvin values represent warm (yellowish) light temperatures.  

Generally speaking in a residential space, I like to choose lights within the 3000-4000 Kelvin range. Use the chart below to determine which light temperature you'd like best.

Pro Tip:  In a room or open concept space, it’s best to choose lighting that shares the same temperature rating (Kelvin rating) to ensure a complimentary and cohesive design.

INCANDESCENT LIGHT
An incandescent light bulb is one where a wire filament is heated until it glows with light. The process of generating light in this way requires a lot of energy and that’s why we now refer to this type of light bulb as inefficient.

HALOGEN LIGHT
Halogen light bulbs are very similar to incandescent light bulbs. They work relatively the same, except that halogen light bulbs have tungsten filaments that are surrounded by a quartz casing and filled with iodine and bromine gases. Halogen bulbs are slightly more efficient than incandescent, but not notably.

CFL LIGHT
Compact fluorescent light (CFL) bulbs provide energy-saving light in a compact fluorescent tube. These were originally designed to replace incandescent light bulbs because of their efficiency.

LED LIGHT
LED lights produce light via Light Emitting Diodes, hence the name LED. The explanation of how light is produced via LED is quite technical so let’s just say that this is a type of light that requires very little energy to produce a considerable amount of light.

You still with me?  Now that you know what these terms mean, it’s easier to determine how much light is needed in a room because now you can compare apples to apples. Here’s what I mean….

Often times people get confused because they don’t understand what each of these terms mean and what they measure.  Now you know that if you want to know how bright a light is, you need to look at its Lumen level.   If you want to know how much energy it will take to light a bulb, you need to review the wattage. Lastly, if you want to know how the light will appear in terms of colour (cool or warm) you need to evaluate Kelvins. Therefore, it doesn’t matter if you are comparing incandescent or LED or other lighting types such as CFL or halogen.  Each light bulb type should include a measurement of Watts, Lumens and Kelvins so that you can compare each unit effectively.  Make sense?

Okay, okay so you understand all the technical stuff, but I still haven’t told you how much light you need to light a room.  Don’t worry; I’m a woman of my word so here it goes:

GENERAL RULES FOR LIGHTING
Please note that these are GENERAL rules to determine how much light is needed in a room. I've included a range to account for small and large spaces.

1. First, identify the room you are going to light
2. Next, pinpoint the number Lumens that are generally used to light that particular room type (refer to LIGHTING REQUIRED chart below)
   
   
   
   
   
3. Then, calculate the number of Lumens required per TASK area and add them to the number of Lumens required to light the GENERAL space
4. Now, use the WHAT IS A LUMEN chart below to select your bulb type (incandescent, LED, etc.)
   
   
   

CHOOSING YOUR LIGHT
Once you have determined how many Lumens are required to adequately light your room, it is then time to select your light fixtures and bulbs. Make sure that the sum of the Lumens in all the fixtures/bulbs is equal to or greater than your calculation so that your space is bright enough. If your calculation doesn’t exactly match your light fixtures' Lumen count, then err on the side of over-lighting rather than under-lighting; you can always add a dimmer - in fact, I encourage you to do so. Dimmable lighting helps to save on energy costs and helps you to control the mood you want to create in your space.

CALCULATION EXAMPLE
In this example, I will calculate the lumens required to effectively light an average sized kitchen.

NOTE: Calculations may vary depending on the number of bulbs required per fixture. I hope this provides you with enough guidance to determine how to calculate what is needed for the light fixtures you choose.  If not, please contact us to design your lighting plan.

Hopefully, you found this helpful. If you liked this article, please share it with your friends. If you have any questions or you'd like help with your interior design project check out our services or feel free to contact me; I'd love to help you.

Lastly, if you’d like a FREE copy of our Lighting General Rules Cheat Sheet, as well as other interior design checklists & guidelines, join our Design Tribe. 

Thanks for reading and until next time, I hope your days stay bright. :)

Val Malnar
Principal Designer | Orangetree Interiors

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