Downlight Cut-Out Size Chart, Family by Family
Most cut-out charts are a column of hole sizes. This one tells you which part of each downlight family decides the cut-out size, how to measure the hole you’ve got, and which fields to confirm. The hole size belongs to the model, and we’d rather send you the right figure than print a rounded one.
What decides the cut-out in each family
Rows are the five downlight families. Read across to see how the body is built, how it mounts and which part of it sets the hole. The final column holds no numbers on purpose.
| Family | Body / housing construction | Mounting | What decides the cut-out | Confirm before ordering | Per-model values |
|---|---|---|---|---|---|
| GU10 / MR16 frames & housingsFittings | Frame or housing that holds a separate GU10 or MR16 lamp. Housing lines in aluminium, iron and plastic. | Frame fixes into the ceiling opening; fixing method per model (F11). | The housing’s outer body, not the lamp. | F1 · F2 · F3 · F10 · F11 · F12 | per-model — confirm on spec sheet |
| COB downlightsComplete light | COB source behind a reflector. Twin-head recessed, adjustable-angle and anti-glare versions. | Recessed or surface, per model (F11). | The body and reflector of the specific model; twin-head fittings take a rectangular opening. | F1–F12 | per-model — confirm on spec sheet |
| SMD integrated & panel downlightsComplete light | SMD LEDs on a board behind a diffuser, in integrated and panel bodies. | Recessed or surface, per model (F11). | The panel or body outline of the specific model. | F1–F12 | per-model — confirm on spec sheet |
| E27 downlights & bodiesBody + separate lamp | Downlight body built around an E27 lamp holder; the lamp is its own order line. | Recessed or surface, per model (F11). | The body diameter; lamp choice changes the depth needed (F3). | F1 · F2 · F3 · F10 · F11 · F12 | per-model — confirm on spec sheet |
| Smart WiFi downlightsComplete light · networked | Networked complete light with app control, dimming and CCT adjustment on selected models. | Same as non-smart: recessed or surface, per model (F11). | The body of the specific model, by the same rule as a non-smart downlight. | F1–F12 + app / gateway / voice-platform check | per-model — confirm on spec sheet |
Measure, match, confirm
Measure the hole, not the old fitting
On a retrofit, take the old fitting out and measure the opening itself, in more than one direction: ceiling holes are rarely perfectly round, and the smallest reading is the one that limits you. Note the board thickness while you’re there, because spring clips need something to grip. On a new build there’s no hole yet, so F1 from the chosen model’s sheet becomes the cutting instruction.
Match the family boundary
Find your fitting’s row in the boundary table. In a GU10 or MR16 frame, the housing decides the hole; in a COB or SMD downlight it’s the body of the complete light; in an E27 body it’s the body diameter, with lamp choice changing the depth. Knowing which part sets the hole stops you comparing the wrong figures.
Confirm the F-fields
Send the measured hole, the ceiling type and the F-codes that matter on your job. For a straight swap that’s usually F1, F2, F3 and F11; for a complete light add F4 to F9. We answer from the spec sheet of the exact model, never from a family average.
Confirm these fields before you cut or order
F1 to F3 decide whether the fitting goes in. The rest decide whether it’s the light you meant to buy.
| Code | Field | Why it matters | Value for your model |
|---|---|---|---|
| F1 | Cut-out size | The hole in the ceiling. On a retrofit it has to match the hole that’s already there; on a new build the hole is cut to this figure. Check shape as well as size. | per-model — confirm on spec sheet |
| F2 | Face diameter | The visible trim. It has to overlap the cut edge, so it’s always a different figure from F1. Never read one as the other. | per-model — confirm on spec sheet |
| F3 | Body height | Depth above the ceiling line, including anything attached to the body. It has to clear joists, ducts, pipes and insulation in the void. | per-model — confirm on spec sheet |
| F4 | Power | Sets driver choice and circuit loading. Quote it per model; a family name alone doesn’t fix it. | per-model — confirm on spec sheet |
| F5 | Light source: COB or SMD | COB gives one concentrated source behind a reflector; SMD spreads LEDs across a board. It changes the lit face and the glare control. | per-model — confirm on spec sheet |
| F6 | CCT range | Colour temperature on offer for the model, fixed or selectable. Match it across every fitting in one space. | per-model — confirm on spec sheet |
| F7 | CRI | Colour rendering. It matters most where people judge colour: shops, restaurants, galleries, hotel rooms. | per-model — confirm on spec sheet |
| F8 | Dimmable or not | Whether the model dims, and by which method. It has to suit the dimmer or control system on site. | per-model — confirm on spec sheet |
| F9 | CCT-adjustable or not | Whether colour temperature can be changed after installation, and how it’s switched. | per-model — confirm on spec sheet |
| F10 | Housing material | Aluminium, iron or plastic. Affects weight, finish and how heat leaves the body. | per-model — confirm on spec sheet |
| F11 | Mounting | Recessed or surface, plus the fixing method. Surface models need no cut-out, so F1 drops out of the check. | per-model — confirm on spec sheet |
| F12 | Warranty | Varies by model. Take the term from the spec sheet of each model on the order, never from a family. | per-model — confirm on spec sheet |
Four ways a cut-out goes wrong
- Reading face diameter (F2) as the hole size, so the hole ends up too big for the trim to cover.
- Measuring the old fitting instead of the hole. The old trim hides the real opening.
- Forgetting body height (F3). The fitting fits the hole but not the void above it.
- Assuming one family shares one hole size. Models within a family differ, which is why every value cell here reads per-model — confirm on spec sheet.
For the longer version, with worked measuring practice, read the LED downlight cut-out size guide. For mounting and fixing questions see recessed downlights.
Send the hole size and the F-codes you need confirmed
We reply with values from the spec sheet of the model that fits your ceiling: cut-out, body height, optics, dimming and warranty, field by field.