Until about ten years ago, choosing a bulb was simple. You picked a wattage — 40, 60, 100 — and the higher the number, the brighter the bulb. Wattage was brightness, more or less, and everyone understood it.
Then LEDs arrived. A 9-watt LED bulb produces roughly the same light as a 60-watt incandescent. The old equation broke. And rather than help, most bulb packaging now leads with both numbers, then a third (lumens), then a fourth (equivalent watts), and people end up more confused than before.
Here's the plain explanation. What lumens and watts actually mean, how they relate, and which one you should care about.
The short version
If you don't want to read the rest of this article:
- Lumens tell you how bright a bulb is.
- Watts tell you how much electricity it uses.
- Always pick on lumens. Treat watts as a separate concern about your energy bill.
For a rough starting point: a traditional 60W bulb produced about 800 lumens. An LED giving you that same 800 lumens will use around 8 watts. That's the trade — same brightness, an eighth of the electricity. The Energy Saving Trust estimates that replacing every incandescent bulb in an average UK home with LEDs saves around £55 a year on electricity bills.
Divide old incandescent wattage by 7 or 8 to get the equivalent LED wattage. So a "60W equivalent" LED uses about 8 watts. A "100W equivalent" uses about 14 watts.
What is a lumen, really?
A lumen is the formal SI unit for luminous flux — the total amount of visible light a source emits in all directions, weighted by the human eye's sensitivity to different wavelengths. The standard is defined and maintained internationally by the International Commission on Illumination (CIE), the body that governs how light is measured worldwide.
In simpler terms: one lumen is roughly the light produced by a single candle, measured one metre away. It's a unit of light output, full stop — independent of how much energy was used to produce it.
This is the number that matters when you're choosing a bulb. It tells you what you'll actually see. Everything else — wattage, technology, brand, price — is secondary.
Lumens by room: how much do you actually need?
Brightness recommendations are usually given in lumens per square metre. Multiply by the area of your room (length × width in metres) to get your total target.
| Room type | Lumens per m² | 3m × 4m room (12m²) |
|---|---|---|
| Living room | 200–300 | 2,400–3,600 |
| Kitchen (general) | 300–400 | 3,600–4,800 |
| Kitchen (task areas) | 500–800 | worktop targeted |
| Bedroom | 100–200 | 1,200–2,400 |
| Bathroom | 300–500 | varies by zone |
| Dining room | 200–300 | 2,400–3,600 |
| Hallway | 200–300 | spread evenly |
| Home office | 400–500 | 3,000+ for desk task |
| Utility / workshop | 500–700 | generously over-lit |
These ranges are broadly consistent with guidance published by the Lighting Industry Association, the UK trade body for lighting manufacturers, though commercial standards (BS EN 12464 for workplaces) typically demand higher levels than domestic comfort needs.
Two important caveats before you take these numbers as gospel.
First — these are total targets, not single-bulb targets. A living room needing 3,000 lumens doesn't mean one 3,000-lumen ceiling fitting. It means 3,000 lumens distributed across three or four sources — a ceiling fitting, a table lamp, a floor lamp, perhaps a wall light. The three-layer principle we wrote about elsewhere applies here. For living-space examples, browse our living room lighting, where most pieces sit comfortably in the 400–800 lumen range — the right scale for ambient or accent use rather than overhead floods.
Second — these numbers assume mid-range ceiling height (around 2.4m), mid-tone walls, and average reflectivity. A room with dark walls, a high ceiling, or matte surfaces will swallow light; you may need 20–30% more than the table suggests. A bright white minimalist room with reflective surfaces gets away with less.
Room-by-room in more depth
The numbers in the table aren't arbitrary — they reflect how the room is used.
Kitchens need the brightest general lighting in the house because they're working spaces. The 300–400 lm/m² figure is for ambient fill, but worktops, hobs and prep areas need much more — typically 500–800 lumens directly over the surface. This is why kitchen lighting tends to combine ceiling-mounted ambient pieces with targeted pendants or under-cabinet task strips.
Bedrooms work the opposite way. Bright ambient light in a bedroom is jarring at the end of the day; the eye doesn't want to be working hard when it's preparing to sleep. The 100–200 lm/m² range is deliberately low, and most of that comes from bedside lamps and softer wall-mounted pieces rather than a powerful overhead. Our bedroom lighting collection leans towards lower-output, warmer-toned pieces for exactly this reason.
Bathrooms are zone-specific. General fill might be 300 lumens per square metre, but the mirror area needs much brighter task lighting (typically 500+ lumens directed at the face) for shaving, makeup, and any close work. UK regulations require specific IP ratings depending on bathroom zone — we cover this in our forthcoming bathroom IP zones article.
What does wattage tell you, then?
Watts measure energy consumption — how much electricity the bulb draws from the wall while it's on. Lower watts means lower running cost. A 60W incandescent left on for 4 hours a day costs roughly four times as much to run as an 8W LED giving the same brightness.
So watts matter for your bill, not your room. Once you've picked a bulb on lumens, glance at the wattage to make sure it's an efficient bulb — but don't choose the bulb on wattage.
What counts as "efficient" for an LED?
The number worth knowing: lumens per watt, or lm/W. It's the conversion rate — how much light a bulb squeezes out of each watt of electricity.
- Old incandescent: 10–15 lm/W. Most energy turned to heat, not light.
- Halogen: 15–25 lm/W. Slightly better than incandescent, still mostly heat.
- CFL (compact fluorescent): 50–70 lm/W. A big leap, but with the slow warm-up and harsh colour quality people remember.
- Modern LED: 80–120 lm/W. Excellent efficiency, near-instant on, good colour quality.
- Premium LED: 120+ lm/W. Best-in-class energy performance.
If you're choosing between two LED bulbs at the same lumen output, the one with lower wattage (and therefore higher lm/W) is the more efficient choice. Over the bulb's lifetime, the savings on the more efficient one can amount to £10–£30 per bulb in electricity costs.
The "watt equivalent" claim, decoded
Most LED packaging says something like "60W equivalent" alongside the actual wattage of 8W or 9W. This is the manufacturer telling you "this will be as bright as the 60W incandescent you grew up with".
The conversion is roughly:
| Old incandescent | Equivalent lumens | Typical LED wattage |
|---|---|---|
| 25W | ~220 lm | 2–3W |
| 40W | ~450 lm | 4–6W |
| 60W | ~800 lm | 7–9W |
| 75W | ~1,100 lm | 11–13W |
| 100W | ~1,600 lm | 14–17W |
| 150W | ~2,600 lm | 22–25W |
If you grew up choosing incandescent bulbs and you're trying to replicate the brightness of the bulb you've always used, the "equivalent watts" claim is the shortcut — just match the old number.
One caveat: equivalent claims must be supported by lumen data, but how manufacturers calculate "equivalent" varies. Since 2021, all lighting products sold in the UK have carried the revised energy label under the UK Energy Labelling Regulations, which rescaled the rating system and made lumen output a mandatory disclosure on packaging. Always cross-reference the equivalent claim with the lumen figure, which is independently measured to a standard.
How to think about it in practice
Walk through a typical bulb-buying decision:
- How bright do you need it? Calculate your room's lumen target from the table above, then divide across the fittings in that room.
- Pick on lumens. Find a bulb that delivers the lumens you've worked out, in the right fitting type, with the right colour temperature (2700–3000K for living spaces, see the linked article for details).
- Glance at wattage. Is it 80+ lumens per watt? Good. Below that, look for a more efficient alternative — the better LED will pay for itself.
- Check it's dimmable if you're using a dimmer (almost always worth it in living spaces).
- Buy two. Keep one as a spare. LED packaging changes constantly and the bulb you love now may not be available in 12 months.
Why this confusion exists at all
For about a century, incandescent bulbs were the only domestic option, and they were so inefficient that wattage was a near-perfect proxy for brightness. A 60W incandescent always produced about 800 lumens. The two numbers were locked together, and "watts" became shorthand for "how bright a light is".
LEDs broke the link. A 9W LED produces 800 lumens. A 9W CFL produces about 500. A 9W halogen produces around 150. The wattage now tells you almost nothing about the light output — only about the energy consumed.
The industry has gradually pushed lumens as the new standard — EU and UK regulations have mandated lumen disclosure on packaging for over a decade — but consumer habit dies hard. Most people still ask "what wattage?" when they should be asking "how many lumens?". This article is our attempt to nudge that needle a little.
The Enso take
Stop thinking about wattage as a measure of brightness. It's a measure of how much you'll pay to run the bulb — useful, but secondary. Lumens tell you what you'll see. Pick on those, every time, and trust that an efficient modern LED will keep your electricity bill modest as a side effect.
If you'd like a sanity check on the bulbs for a specific room, write to us. We've spent a lot of time thinking about this stuff and we're happy to help you avoid the common mistakes.
