2700K or 4000K ? Choosing Colour Temperature, Room by Room

Amber glass mushroom table lamp glowing warm white in a dark room

You choose a light you love, wait a fortnight for it to arrive, fit it, switch it on, and the room feels wrong. Not the fitting. The bulb.

Colour temperature is the number on the box nobody reads, and it undoes more good lighting in British homes than any other single decision. It is measured in kelvin, written as a number followed by K, and it is the difference between a room that feels like an evening and a room that feels like a waiting area.

On this page

What the numbers actually mean

The kelvin scale runs backwards from how most people expect. Low numbers are warm and orange. High numbers are cold and blue.

  • 2200K — candlelight, and the amber glow of a vintage filament bulb.
  • 2700K — warm white. The colour of a traditional incandescent bulb, and the one we recommend for almost everything at home.
  • 3000K — soft white. Very slightly crisper. Common in downlights and integrated LED fittings.
  • 4000K — neutral or cool white. Office light. Useful over a worktop, wrong in a sitting room.
  • 5000K to 6500K — daylight and cool daylight. Garages, utility rooms, a workshop. Almost nowhere else in a home.

Here is the part that is easy to miss: kelvin has nothing to do with brightness. A 2700K bulb is not dimmer than a 6500K one. They can put out exactly the same light. Brightness is lumens, and it is a separate decision entirely. Which cap the bulb needs is a third, separate question: bulb fittings explained. How much light each room needs is in how many lumens do I need.

The short answer

2700K everywhere you relax. 3000K where stone, marble or a cool grey scheme needs crisping up. 4000K only where you genuinely work. 6500K essentially nowhere.

If you read no further than this paragraph, you will get more than nine rooms out of ten right.

Amber glass mushroom table lamp giving a warm glow on a bedside table

The Amber Glass Mushroom Table Lamp is 2700K behind tortoiseshell glass, which is about as warm as a room gets before it turns orange. It is one of our bestsellers, and the warmth is the reason.

Room by room

Living room: 2700K

There is no argument to be had here. A sitting room is used in the evening, and warm light is what the eye expects after dark. Put 2700K in the living room ceiling fitting, in the floor lamps, in everything.

Better still, do not light a sitting room from the ceiling alone. Three warm sources at different heights — a pendant, a floor lamp in the corner, a table lamp on the side table — will beat one bright ceiling light at any temperature. The full five-source method is in how to light a living room, and if the room has no ceiling rose at all, how to light a room with no ceiling light.

Bedroom: 2700K, and dimmable if you can

Warmer still if anything. Blue-weighted light in the hour before bed is the one piece of lighting folklore that has real evidence behind it, and a 4000K bulb beside a bed is working against you.

Our bedroom lighting is chosen around that. The Rattan Table Lamp is 3000K behind a woven shade, which lands warm; the Rechargeable Wall Light dims by remote, which is the easiest upgrade there is for a room with a single switched ceiling light. Bedside heights are in how to light a bedroom.

Kitchen: 2700K over the island, 4000K under the cupboards

This is the one room where two temperatures are defensible, because a kitchen does two jobs.

Decorative light — the pendants over the island, the ceiling fitting over the table — should be 2700K, because that is the light you eat and talk under. Task light, meaning the strip under the wall units where you actually chop, can be 4000K without anyone minding, because it is hidden and it is only on while you cook.

The rule that keeps this from becoming a mess is in never mix two temperatures in one sightline, below. Where each layer goes is in how to light a kitchen, and our kitchen lighting collection is chosen on the decorative side of that line.

Bathroom: 2700K to 3000K

Most British bathrooms are over-lit with cold white, and the result is unflattering in a mirror at seven in the morning. 2700K around a mirror is kinder and perfectly usable; 3000K is the coolest we would go.

The Wabi-Sabi Wall Light is a warm 9W LED made for mirror height, and the Travertine Stone Ceiling Light is 3000K. Both sit in bathroom lighting. Where a fitting may go in a bathroom matters as much as its temperature: bathroom lighting zones explained.

Home office: 4000K, but only on the desk

This is the one room where cool white earns its place. Neutral white light genuinely helps concentration during the working day, and a desk lamp is the right place for it because you can switch it off at six o'clock and let the room go warm again.

The LED Desk Lamp dims and shifts temperature, which is exactly what a desk wants. The Gold Desk Lamp is the same idea with more presence. What should not be 4000K is the ceiling fitting: light the room warm and the desk cool, not the other way round. Which side the lamp goes, how high, and why the window belongs beside the desk rather than in front of it, are in home office lighting.

Hallway and stairs: 2700K

A hall is the first thing you see coming in from a cold street. It should feel warm before you have taken your coat off. Our hallway lighting favours flush and semi-flush fittings for the low ceilings most halls have; the Nordic Wall Light is the quiet version for a narrow corridor. Spacing is in hallway lighting for low ceilings.

Outdoors: 2700K

Warm white outside reads as somebody being home. Cool white reads as a car park. It is the single most visible lighting mistake on a British street, and it is covered in full in our guide to where to put an outdoor wall light, along with the heights and the IP ratings. Beyond the front door — paths, patios and planting — the same warm rule applies: garden lighting ideas. Everything is in outdoor lighting.

Utility, garage, loft: 4000K and up

Finally, somewhere cool white belongs. You are looking for things in boxes, not settling in for the evening. The 36W Minimalist Gold Flush is 6500K and honest about it, and the LED Ceiling Spotlight is 6000K.

Gold ringed LED flush ceiling light giving a cool white output

Why the same bulb looks different in two shades

Buy two identical 2700K bulbs, put one in a clear glass pendant and one behind a linen shade, and they will not look the same.

  • Clear glass shows you the filament. It looks warmer and more sparkling, and it glares if the bulb is too bright. Our Industrial Glass Pendant is a clear shade, and it wants a low-output warm bulb, not a bright one.
  • Opal or frosted glass diffuses everything and reads slightly cooler and calmer. The Glass Pendant Light is the example.
  • Fabric, paper and rattan warm the light on the way through. A rice paper lamp or a woven bamboo shade will make a 3000K bulb behave like 2700K — and a weave does more than warm it, as set out in rattan and bamboo lights.

Which is why, if you are unsure, a warm bulb behind a natural shade is the safest combination in the house.

The number that matters more: CRI

Colour temperature tells you what colour the light is. CRI, the colour rendering index, tells you how honestly that light shows the colours of everything it lands on. It runs to 100, and it is the number that separates a cheap LED from a good one.

  • CRI 80 — the usual minimum. Acceptable in a hallway.
  • CRI 90 and above — what you want anywhere you look at people, food, fabric or paint. Skin looks alive rather than grey.

If you have ever repainted a room because the colour looked wrong in the evening, low CRI was probably the culprit rather than the paint. Buy CRI 90+ bulbs for the living room, the dining table and the bathroom mirror. They cost a pound or two more and it is the best-value decision in this entire guide.

How bright, in lumens

Watts measure consumption, not light. Lumens measure light. As a rough guide for total light in a room, with a 2.4 metre ceiling:

  • Living room — 1,500 to 3,000 lumens, split across three or four fittings.
  • Bedroom — 1,000 to 2,000 lumens total.
  • Kitchen — 3,000 to 4,000 lumens, because it is a workroom.
  • Bathroom — 2,000 to 3,000 lumens.
  • Beside a bed or a chair, for reading — 400 to 600 lumens is plenty from a single lamp.

Split the total across several fittings rather than loading it into one. A single 3,000 lumen ceiling light and three 1,000 lumen lamps use the same electricity and produce completely different rooms.

Never mix two temperatures in one sightline

This is the rule that does the most work, and almost nobody is told it.

The eye cannot judge colour temperature in isolation. It can judge it instantly by comparison. One 4000K bulb among four 2700K ones does not look neutral, it looks broken, and it will draw your eye every time you walk into the room.

So: everything you can see at once should be the same temperature. In an open-plan kitchen-diner, that means the pendants over the island and the fitting over the table match, even though the two ends of the room do different jobs. Task lighting can differ only when it is concealed, such as under a wall unit or inside a cupboard.

It follows that if you are replacing one blown bulb in a cluster like the 4-Bulb Dining Cluster, replace them all, or keep a spare of the identical bulb. Two bulbs a year apart rarely match.

A word on dimming

An incandescent bulb warmed up as it dimmed, which is why candlelit dimming felt so good. Most LEDs do not: dim them and you get less of the same colour.

Two ways round it. Look for bulbs described as warm dim or dim to warm, which drop from 2700K towards 2200K as they go down. Or buy a fitting with switchable temperatures built in, like the LED Floor Lamp, which offers 3000K, 4000K and 6000K from one lamp, or the Rechargeable Table Lamp, which does the same at bedside scale and needs no cable.

Minimalist dimmable LED floor lamp with a scalloped fabric shade

Two practical warnings. Not every LED is dimmable, and a non-dimmable LED on a dimmer will flicker or buzz. And old dimmer switches designed for filament bulbs often misbehave with LEDs: if yours flickers at the bottom of its range, the switch is usually the problem, not the bulb — the full diagnosis is in why do LED lights flicker.

Five mistakes worth avoiding

  1. Buying on watts. Watts tell you the running cost. Lumens tell you the light.
  2. Cool white in a sitting room. The commonest mistake in British homes, and the most easily fixed: it costs the price of a bulb.
  3. Mixing temperatures in one room. One odd bulb spoils four good ones.
  4. Ignoring CRI. 2700K at CRI 80 still makes a room look flat. Pay for 90+.
  5. Lighting a whole room from the ceiling. No colour temperature rescues a single central pendant doing all the work. See how high should a pendant light hang and what size table lamp do I need for the two fittings that fix it.

In short

  • Living room, bedroom, hallway, outdoors: 2700K.
  • Bathroom: 2700K to 3000K.
  • Kitchen: 2700K decorative, 4000K concealed task light only.
  • Desk: 4000K, on the lamp, not on the ceiling.
  • Garage and utility: 5000K to 6500K.
  • CRI: 90+ anywhere you look at people or food.
  • Rule above all others: one temperature per sightline.

Common questions

Is 2700K or 4000K better for a living room ?

2700K, without hesitation. A living room is used in the evening, when the eye expects warm light, and 4000K reads as an office. Keep 4000K for a desk lamp or a concealed worktop strip.

What does K mean on a light bulb ?

K stands for kelvin and describes the colour of the light, not its brightness. Low numbers such as 2700K are warm and orange; high numbers such as 6500K are cold and blue. Brightness is measured separately, in lumens.

What colour temperature is best for a bathroom ?

2700K to 3000K. Cool white around a mirror is unflattering first thing in the morning, and it makes a small bathroom feel clinical. Pair a warm temperature with a CRI of 90 or above so skin tones look right.

Can I mix warm white and cool white in the same room ?

Only where the cool source is concealed, such as a strip under a kitchen wall unit. Anything you can see at once should share one temperature: the eye judges colour by comparison, so a single odd bulb stands out immediately.

How many lumens do I need in a room ?

Roughly 1,500 to 3,000 lumens for a living room, 1,000 to 2,000 for a bedroom, 3,000 to 4,000 for a kitchen and 2,000 to 3,000 for a bathroom, with a standard 2.4 metre ceiling. Split the total across three or four fittings rather than one.

What is CRI and does it matter ?

CRI is the colour rendering index, a score out of 100 for how truthfully a light shows colours. Below 80, paint, food and skin look flat and grey. Choose 90 or above anywhere you look at people or eat.

Why do my LED bulbs flicker when dimmed ?

Either the bulb is not dimmable, or the dimmer switch is an older type designed for filament bulbs and cannot handle the low load of an LED. Check the bulb first, then the switch.

One bulb, one evening

If you take one action from this guide, buy a single 2700K, CRI 90 bulb, put it in the lamp you use most in the evening, and look at the room. That is the whole argument, for about four pounds.

If you would like a hand choosing temperatures for a particular room, write to us at contact@thelightheritage.com. We answer every message ourselves.

Browse table lamps, ceiling lights and wall lights, or start with what other people are choosing in our bestsellers.