Thinking About Downlights, Take a Look at Our Guide

Recessed Downlight


Recessed downlights are a versatile light source for homes and offices. They can fulfil any of the three main lighting roles: general lighting, task lighting, and accent lighting.

This information enables you to calculate how many lights you need and what type.

How Many Downlights Do I Need?

A simple method for estimating the number of downlights required is as follows:

Step 1: Multiply the room’s width by its depth to ascertain the size in SQM.  So if a living room is 3m x 3m it is 9sqm.

Step 2: As a guide I use 1 light per 1.5m in living rooms, I normally increase this to 1 light per SQM in kitchens and bathrooms. .  So in our living room example I would divide the 9sqm by 1.5 giving 6 downlights.

Step 3: A suggested light output for a 9Sqm living room is 1000-2000 lumens(see the lighting calculations section below) so 6 downlights each with an LED 5w 300 lumen output lamp would give 1800 lumens in total.  A dimmer switch could be incorporated so lighting level can be changed with the mood.  A higher wattage lamp would give more lumens in an area that needs to be brighter.

This is a guide only and you should contact your local registered electrican for more specific advice.

Ceiling Height

The coverage area of a downlight depends on the beam angle of the light source and the height of the ceiling. A flood beam spotlight naturally lights a greater surface area than a narrow beam, but with less intensity (assuming the two emit an identical amount of light in lumens).


Recessed downlights are generally positioned 40-50cm away from walls with a space of around 1-1.3m between each light. Dividing the ceiling height by two is a way of gauging how much space to leave between each downlight. Thus, if your ceiling is 2m high, place your lights 1m apart.

Beam Angles and Fire Ratings

A narrow spot beam gives an intense light for task applications and is useful for highlighting small display items. Choose a recessed downlight with a flood beam for general lighting. Those with an adjustable head can be aimed at pale-coloured walls or cupboards to spread light.

Any fire-rated ceiling, which is usually one beneath an occupied floor, needs a fire-rated downlight to be installed. This prevents an early ceiling collapse in the event of a fire, allowing crucial evacuation time for anyone above.


IP Ratings

When installing downlights in a bathroom you’ll generally need a product with a minimum IP44 rating.   Ask your electrician for further information on IP ratings.


Choose dimmable downlights to create mood and save energy. Contrasting areas of light and dark invariably add atmosphere to a room. You might use dimmable downlights for general lighting, turning them down for intimate effect while giving greater emphasis to floor lamps, table lamps, picture lights or wall lights.  LED lamps need specific dimmers.

How to Calculate How Much Light A Room needs

A foot-candle is how bright the light is one foot away from the source. Lighting requirements/needs vary depending on the type of room being lit. For example, a bathroom or kitchen will require more foot-candles than a living room or bedroom.

Room                    Foot Candles Needed

Living Room       10-20

Kitchen                 30-40

Kitchen Stove    70-80

Kitchen Sink        70-80

Dining Room      30-40

Bedroom             10-20

Hallway                5-10

Bathroom            70-80


Determine the Needed Lumens

lumen is a unit of measurement of light. A lumen is a way of measuring how much light gets to what you want to light. To determine the needed lumens, you will need to multiply your room Square footage(it will need to be in square foot not metres) by your room foot-candle requirement.

For example, a 100 square foot living room, which needs 10-20 foot-candles, will need 1,000-2,000 lumens. A 100 square foot dining room, which needs 30-40 foot-candles, will need 3,000-4,000 lumens.

Practical Advice

Downlights look great and give levels of lighting a central light cannot achieve.  However, Installing downlights is an invasive process that will cause dust and there may be areas around the downlight that need making good.  If your house is older that 1940’s it probably has a plaster and lathe ceiling that may crack when the downlights are installed.  None of this is the end of the world as all can be made good.

If there is no access above the downlights i.e in the loft or taking the first floor floorboards up it still may be possible to install the downlights.  Ask your local registered electrician for advice on this.
For advice on downlight installations or a free quote call Anthony on 020 8914 8297.

Wandle Electrical Services are based in Wallington and cover Sutton, Carshalton, Croydon, Purley, Wimbeldon and surrounding areas.

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Your Local Electrician

Anthony Jones

I'm an electrician based in Surrey. I run two small family business called Wandle Electrical Services  and The London Electric Radiator Company. I'm also a MCS certified solar panel installer.