When shopping for LED downlights you need to consider what size lights are best for your situation. Recessed ceiling lights, or downlights, are the most popular form of residential lighting as they are minimalist in design and sit flush with your ceiling line. The two common sizes for residential lights are:
- For a 70mm diameter ceiling cutout, and
- For a 90mm diameter ceiling cutout.
Read on to find out whether 70mm or 90mm is best for you.
Size generally determines brightness
Generally, the larger a LED downlight the larger the LED chip or chips are, and that means the brighter the light. The following brightness ranges are typical for each LED light size:
| Light size (cutout diameter) |
Watts | Lumens | Halogen light equivalent brightness |
| 70mm | 9W to 12W | 500 to 900 | 35W to 50W |
| 90mm | 12W to 18W | 800 to 1100 | 45W to 60W |
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What brightness is required for my space?
There are some rules-of-thumb, as listed below, but adjustments should be made for higher ceilings, darker furnishings, light escaping the space, and room shapes.
For areas that do not need high brightness, such as dining rooms and hallways, a target about 150 to 200 lumens per square metre (at floor level) is normal. So a 8m x 1.1m hallway (about 9 square metres) will need up to 1800 lumens. Therefore 3 x 90mm lights would be excessively bright, but 3 x 70mm lights would be ideal.
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For areas that require higher brightness, such as kitchens and workspaces, about 200 to 600 lumens per square metre (at floor level) is normal. So a 5m x 3m kitchen (15 square metres) will need up to 9000 lumens. Therefore an array of 8 x 90mm lights (i.e. 4 x 2 layout) would be ideal, but if you were using 70mm lights you may need 10+ lights (ie 5 x 2 layout).
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Some workspaces and commercial food preparation spaces seek much higher brightness than the above – and I would always recommend you get specialist advice for specialist applications.
When would I use a 70mm downlight?
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Replacing 70mm lights - If you are replacing halogen downlights that had a 70mm cutout then it is simpler to use LED downlights for a 70mm cutout. Then you will not need to have all the ceiling holes resized!
Smaller spaces – Hallways, bathrooms, smaller rooms and alcoves do not require very bright downlights. Generally, 70mm lights are better for such narrow and smaller spaces so that glare and over-brightness is not experienced.
Spaces that do not need high brightness – dining rooms, hallways, media rooms and some relaxation living rooms generally do not need high brightness, and 70mm lights may be more appealing.
To achieve even brightness - Often you can get a more even light spread from using 70mm lights than 90mm lights in some spaces. If you opt for 70mm lights they can be closer together and therefore the light beams overlap more to provide a more uniform room brightness. For example, in a compact 4m x 4m bedroom here are the light array options:
- 4 x 90mm lights - would be too bright for the space and an LED dimmer would be essential to moderate the brightness.
- 2 x 90mm lights – overall brightness would be satisfactory, but wall shadowing and evenness of brightness may be a problem
- 4 x 70mm lights – my preference as the brightness would be perfect and the overlapping of the four light beams would create very even brightness for the space
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When would I use a 90mm downlight?
Replacing 90mm lights - If you are replacing halogen downlights that had a 90mm cutout then it is simpler to use LED downlights for a 90mm cutout. Then you will not need to have all the ceiling holes resized!
Spaces requiring high brightness – as 90mm lights provide higher brightness using these in such areas will be more efficient (as fewer lights will be required)
Larger spaces – Large living areas and kitchens and spaces with higher ceilings can benefit from larger brighter lights as you can use fewer lights. For example, a large 8m x 6m lounge room could use 3 x 2 array of larger brighter 90mm lights, whereas it might require a 4 x 2 array of 70mm lights to achieve the same result.
Photo from www.depositphotos.com
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