How many downlights?

If you’re looking for the short answer to this, you can install 1 downlight per square metre, leaving 1 metre spacing’s between each downlight and a distance of 1/2 a metre from the walls. This would generally get you the correct, bright and even lighting results. As a general rule, this formula serves as a starting point for calculating the number of downlights needed in a room. For a more detailed approach, you can refer to a handy guide that helps you calculate the appropriate number of downlights for your specific space. But this is more of a question of how many downlights per square metre? And does not account for other variables.

The one downlight per square metre formula usually provides sufficient lux levels for the majority of installations. Many contractors and installers have used this method successfully for many years and adapted it to different room shapes and applications. However, the number and placement of downlights should be adjusted based on room characteristics, usage, and desired ambiance—meaning you should determine the quantity of downlights based on the specific needs of each room.

But LED downlighting technology has surpassed halogen, you can get LED downlighters that are much brighter than 50W GU10 mains voltage halogens and 50W MR16 low voltage halogens. You can use brighter downlights with wider beam angles and spread them out further. Rather than cramming lots of downlights together, you can install fewer. This looks better and saves you money on not only having to buy more downlights but also on the installation costs.

For example if you have a brighter LED downlight such as the Bell Lighting Firestay, it has a light output of up to 820 lumens and a wide 60 degree beam angle. You could easily space these 1.5 metres apart and 0.75 metres from the walls; or what about 2 metres apart and 1 metre from the walls? You can certainly get away with the 2 metre spacings in living rooms and bedrooms especially if you’ve got a wider beam angle. In larger rooms or those with higher ceilings, you may need additional downlights to ensure adequate brightness throughout the space. This particular downlight has a wattage switch that goes from 5W at 570 lumens to 7W at 820 lumens as well as a colour temperature switch with 2700K, 3000K, 4000K and 6000K in 1.

However, rooms are used for different purposes and require different levels of brightness (lux). For example; in a kitchen it would be better to have a higher lux level to allow you to see what you’re doing better. For kitchens we recommend an average of 300 lux. Whereas in a lounge where you’re only watching TV, you may only require an average of 150 lux. When planning your lighting, make sure you have enough light distributed evenly throughout the room to avoid dark spots or harsh shadows.

For some unknown reason there are no industry set recommendations for lux levels in homes, probably becausew the lighting industry couldn't agree on them. Specific lux levels are only used for commercial buildings, for example an office should be set at a minimum of 500 lux. When choosing your lighting, always consider how much light is needed for each room type and its intended use. Anything else you read on the internet etc. is a matter of opinion not fact.

Many Variables to Consider

As there are many variables to consider with lighting design, ranging from obvious ones such as the brightness (lumen output) of the downlight you want to install; to more complicated ones like uniformity, maintenance and reflectance factors, we offer a lighting design service to take away the guessing and make it more accurate.

When planning for wet areas, it's important to choose bathroom downlights with the appropriate IP ratings to ensure safety and functionality. We charge a fee of £20+VAT per room, our lighting design service is available here, or send an email with the details of your project including your room dimensions, plans, drawings and any other information you’ve got. We can then send a link for payment. Our £20+VAT charge is per room, not per building. If you have a large property with lots of rooms or a commercial project please contact us. Some room types are quick and easy to do, but some rooms with lots of cupboards and furniture to add, or rooms with apex ceilings or awkward shapes take considerably longer for us to do.

We can then provide you with your own personal lighting plan, using our lighting design software and done by our dedicated Relux and Dialux lighting designer. He’s hungry for work, so please do get in touch, no matter if you’ve got a small bathroom or an entire house. If you have a commercial property we can also arrange for site visits, energy saving advice and cost of ownership analysis. We usually do this in partnership with one of our commercial lighting manufacturers such as Ansell Lighting, Aurora Lighting, Bell Lighting and Collingwood Lighting who specialise in site visits. Our designer can also recommend adjustable downlights, which are ideal for highlighting artwork or architectural features by allowing you to direct light precisely where it's needed.

We’re happy to make recommendations for the best downlights to use, and advise you on the advantages of using energy saving downlights which will also help you to comply with the latest Building Regulations

If you don’t want a lighting design and just need a bit more guidance, we have 5 golden rules to consider:

1. What type of room are you illuminating? Not all rooms need to be illuminated to the same lux levels. Lux is measured in lumens per square metre. Kitchens require a minimum of 300 average lux. Living rooms and bathrooms require 150 average lux and bedrooms only need to have an average of 100 lux. Be sure to determine how many downlights you need in a room to achieve the correct lighting levels.

2. Choose a downlight - It’s best to choose the type of downlight you prefer first then figure out how many you’ll need for each room, as each room is different. Make sure to select the right downlights for each space, considering factors like brightness and energy efficiency.

3. Which beam angle? Some downlights are available in different beam angles. Downlights with wider beam angles can be spread further apart but the beam is less intense as it’s not as focused.

4. Uniformity, there’s no point having overly bright patches in certain areas of a room and dark patches in other areas. You want to make sure that you have a nice even light across the room. Downlights can also be used to focus on a specific area or specific areas within a room, such as reading nooks or art displays, for targeted illumination.

5. Grid layout, a square room looks better with a square grid layout of downlights. If your room is 3x3 metres (9M²) having 9 downlights in 3x3 grid will look neat but your ceiling will be cluttered with downlights. A 2x2 grid, might leave a dull patch in the middle, but adding 1 downlight in the middle won’t look right. This is why having a lighting design can be really useful as you can compare different grid layouts with different downlights before committing to the purchase or cutting holes. Downlight placement is crucial for achieving even illumination and avoiding unwanted shadows or glare.

Here are some useful tables from Aurora Lighting that shows you what lux levels you will achieve with some of their best selling downlights with various room sizes.

When considering reflectance and room features, always take into account the amount of natural light available, as it can influence your overall lighting design and the number of downlights required.

Lighting Design Criteria

1. Dimensions are in metres

2. Based on 2.5M ceiling height

3. Average surface reflectance’s are floor 20%, ceiling 70% and walls 50%. Wall surfaces and the use of wall lights can significantly impact the overall lighting design by enhancing ambiance and providing additional ways to illuminate the space.

4. Working plane measured at 750mm (based on a kitchen worktop).

5. Maintenance factor of 0.85

6. No allowance made for UGR compliance for office use

If you’re interested in our lighting design service to discover how many downlights you need, either order online or email the details of your project and we’ll be in touch. Or follow this link to view our latest range of kitchen lighting products. Different types of lights, such as downlights, plinth lighting, and bulkhead lights, can be used to illuminate specific areas in kitchens and bathrooms for both functional and aesthetic purposes.

Calculating Downlight Quantity

Determining how many downlights you need for a room involves more than just a simple formula - it’s about creating the right balance of light output, energy efficiency, and visual comfort. While a general guideline is to use one downlight for every 1.5 to 2 square metres of ceiling space, this can vary depending on your room’s dimensions, ceiling height, and the specific activities that take place there.

For example, in kitchens and bathrooms where task lighting is essential, you may need more downlights to ensure work spaces like countertops and vanities are well illuminated. In these areas, higher light levels help with food preparation or grooming, so opting for energy efficient LED downlights with higher lumen output is a smart choice. LED downlights not only provide more lumens per watt compared to traditional halogen downlights, but they also offer a longer lifespan and use less energy, making them ideal for both general lighting and accent lighting.

Beam angle is another key factor in your lighting plan. Downlights with wider beam angles can cover a larger area, meaning you may need fewer fixtures to achieve even illumination across the entire ceiling. Conversely, if you choose downlights with a narrower beam angle, you’ll need more downlights to avoid dark spots and ensure the room is evenly lit. This is especially important in living rooms and bedrooms, where you might want to create a welcoming atmosphere with softer, more diffuse light.

Colour temperature also plays a significant role in setting the mood of a room. Warmer tones are perfect for bedrooms and living rooms to create a cozy, relaxing environment, while cooler tones are better suited for kitchens and bathrooms where clarity and brightness are important. Adjusting the number of downlights and their placement can help you achieve the perfect balance between functionality and ambiance.

When planning your lighting, consider the layout of your room and the location of key areas, such as reading nooks, kitchen islands, or bathroom mirrors. Downlights should be spaced evenly to avoid harsh shadows and ensure every part of the room is properly illuminated. For rooms with higher ceilings, you may need more downlights or higher lumen output to maintain the desired light level.

Ultimately, the best way to work out how many downlights you need is to seek professional advice. A lighting expert can help you develop a tailored lighting plan that takes into account your room’s unique requirements, from the number of downlights and their placement to the ideal colour temperature and beam angle. This ensures your space is not only beautifully illuminated but also energy efficient and cost-effective.

Whether you’re illuminating a living room, bedroom, kitchen, or bathroom, taking the time to calculate the right number of downlights will help you create a well lit, inviting space that meets your needs - now and in the future.