A Bulb Has Three Numbers. Most Guides Explain One

The short answer: soft white is 2700K to 3000K and looks warm and yellowish. Daylight is 5000K and above and looks cool and bluish. That is the whole of the comparison every guide gives you, and it leaves out the two numbers that decide whether you like the result. Kelvins set the colour and nothing else, so a 5000K bulb is not brighter than a 2700K one, which is the single most common misunderstanding in this category. Brightness is lumens, and 800 lumens is what replaces an old 60 watt bulb. The third number is CRI, which decides how accurate colours look under that light, and almost nobody mentions it even though it is why food can look grey in a kitchen with perfectly good bulbs in it.

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The three numbers on the box

Almost every article on this subject treats bulb choice as one decision with two options. It is three decisions, they are independent of one another, and mixing them up is why people buy the right colour temperature and still dislike the room.

Kelvins are colour, and only colour

The Kelvin scale runs from around 1000 to 10000 and describes what colour the light is, from candle-orange at the bottom to the blue-white of a stadium floodlight at the top. Soft white sits at 2700K to 3000K. Daylight sits at 5000K and above.

Here is the correction that matters, because I have seen it stated backwards on sites that sell bulbs for a living: a higher Kelvin number does not mean brighter light. It means cooler light. A 2700K bulb at 1600 lumens is considerably brighter than a 5000K bulb at 450, and it will feel warmer while being brighter. If a guide tells you daylight bulbs are brighter, it has conflated two separate specifications, and you will end up with a room that is cold and dim at the same time.

Lumens are brightness

This is the number that replaced wattage and the transition confused everybody. Watts measure energy consumed, which used to correlate with brightness because incandescent bulbs were all similarly inefficient. LEDs broke that relationship: a 9 watt LED and a 60 watt incandescent produce the same light.

So shop by lumens. Eight hundred lumens is the standard replacement for an old 60 watt bulb and is what most ceiling and lamp fittings want. Sixteen hundred replaces a 100 watt. Five hundred is a spotlight or a small accent fitting. Once you know the lumens you need, the Kelvin choice becomes purely about mood rather than about whether you will be able to see.

CRI is the one nobody mentions

Colour Rendering Index scores from 0 to 100 and describes how accurately colours appear under the light compared with natural daylight. A bulb can have a perfect colour temperature and terrible colour rendering, and the result is a room where wood looks flat, skin looks tired and food looks unappetising.

Most cheap LEDs are CRI 80. Better ones are CRI 90 or above. The difference is not subtle in the places it matters, and it costs very little, which is why it is remarkable that a comparison article about bulb choice can run to two thousand words without naming it once.

So the order to decide in is: lumens first, because that is whether you can see. Then Kelvins, because that is the mood. Then CRI, because that is whether everything in the room looks like itself.

Get all three numbers in 3 taps

Room, fitting, and whether you can dim it. Those three give you a colour temperature, a lumen figure and a dimming answer together.

What to use in each room

All three numbers together, by room. The CRI column is the one to read if you have never thought about it before.

Two patterns are worth pulling out. Daylight bulbs appear once in that entire table, in the basement, and that is not an accident: 5000K in a living room reads as an office at nine in the evening, which is the most common lighting regret people have. And the CRI column says 90 or above almost everywhere, because the extra cost is small and the difference in a kitchen or a bathroom is immediately visible.

CRI, and why food looks grey

If you have ever stood in a kitchen with perfectly good bulbs and thought the tomatoes looked dull, you have met a low CRI bulb. It is the third number, it is printed on most boxes, and it is missing from almost every article that compares soft white with daylight.

What the number describes

Colour Rendering Index scores a light source from 0 to 100 on how accurately it shows colours compared with natural daylight. Sunlight contains every wavelength in roughly even proportions, so everything looks like itself. A cheap LED produces an uneven spectrum with gaps in it, and any colour that falls into a gap comes out muted.

Reds suffer most, which is why this shows up in kitchens first. Tomatoes, peppers, raw meat and terracotta all lose their depth under a low CRI bulb. Skin tones go with them, which is why a bathroom can make you look ill at seven in the morning.

Where the line sits

Below 80 is poor and mostly appears in the cheapest bulk packs and older fluorescent tubes. Eighty is the ordinary standard and the default for inexpensive LEDs, and it is acceptable in a hallway or a garage. Ninety and above is where colours look genuinely right, and it is what belongs in kitchens, bathrooms and anywhere you look at people.

The step from 80 to 90 costs remarkably little. Comparable A19 bulbs from the same shelf differ by a small amount per bulb, and the difference in a kitchen is visible the moment you switch them on. It is the best value upgrade in this whole subject and it is the one nobody talks about.

One more thing worth knowing: CRI and colour temperature are completely independent. A 2700K bulb can be CRI 95 or CRI 75, and so can a 5000K one. Choosing daylight does not get you accurate colour, which is a reasonable assumption to make and a wrong one.

The one worth buying: a dimmable CRI 90 bulb at 2700K

This is the specification to look for in a living room or bedroom, and this bulb prints all three numbers rather than leaving you to guess. CRI 90 for colour accuracy, 2700K for warmth, and 800 lumens, which is the standard replacement for an old 60 watt bulb.

It is dimmable, which matters more than people expect. A warm bulb at full output still reads as bright, and the ability to take it down in the evening is what separates a room that feels restful from one that merely has the right colour temperature in it. Rated for 25,000 hours and ENERGY STAR qualified, with no lead or mercury.

One caution the manufacturer states plainly and worth repeating: it is not recommended for fully enclosed fixtures, because heat builds up and shortens the life considerably. If your ceiling light has a sealed glass shade, look for a bulb specifically rated as enclosed-fixture safe instead.

Worth it or skip: Worth it in any room where you look at people, food or wood, which is most of the house. Skip it for a hallway, a garage or a cupboard, where CRI 80 is genuinely fine and the saving across a whole house adds up.

Check the dimmable CRI 90 bulb on Amazon

Three more, by fitting

A CRI 90 six pack, if you are doing a whole room at once. Same 2700K and 800 lumens, same colour accuracy, in a multipack that works out cheaper per bulb. It is non-dimmable, so check your switches first. Worth remembering the rule from earlier: change every bulb in one sightline together, because mixed colour temperatures are more noticeable than a slightly wrong one. See the CRI 90 six pack →

CRI 90+ spotlights, for recessed and track fittings. PAR20 at 500 lumens and 2700K, dimmable, which is the right output for a living room spot where you want a layer of light rather than the whole scheme. Spots are where low CRI shows up badly, because a narrow beam on a single object makes any colour distortion obvious. See the PAR20 spotlights →

A dimmable eight pack, when quantity matters more than CRI. Standard 2700K at 800 lumens, dimmable, in a pack size that covers a whole floor of a house. This is the sensible choice for hallways, landings, cupboards and utility rooms, where CRI 80 is perfectly adequate and the saving is real. See the dimmable eight pack →

Want to see how this fits a whole scheme rather than one bulb? The Scandinavian lighting guide covers layering, and minimalist lighting ideas goes through fittings room by room.

Diagnose a room that feels wrong in 2 taps

The quiz above is for buying. This one is for a room you already live in that is not right.

People also ask about soft white and daylight bulbs

Is daylight or soft white better for a living room?

Soft white, at 2700K, and it is not a close call. Daylight bulbs at 5000K and above read as an office or a shop floor in the evening, which is when you are actually using a living room. The warm end of the scale is what makes a space feel like somewhere to sit down. Keep daylight for a basement, a garage or a utility room, where there is no natural light for it to clash with and the crispness genuinely helps.

Are daylight bulbs brighter than soft white?

No, and this is the most common misunderstanding in the whole subject. Kelvins measure colour, not brightness, and the two are entirely independent. A 2700K bulb at 1600 lumens is twice as bright as a 5000K bulb at 800, while looking considerably warmer. Daylight bulbs can feel brighter because cool light appears more alerting, but the actual output is on the box in lumens. If a guide tells you otherwise, it has conflated two separate specifications.

What colour temperature is best for a kitchen?

Three thousand Kelvin for the general lighting, and 3000 to 4000K for under cabinet task lighting, which can run slightly cooler without clashing. But the number that matters more in a kitchen is CRI: at 80 the food looks grey and the tomatoes look dull, and at 90 or above everything looks like itself. If you only upgrade one room to high CRI bulbs, make it this one.

Can I mix soft white and daylight bulbs in the same room?

Not in the same sightline. The eye adapts to one colour temperature at a time and cannot adapt to two at once, so a mixed room looks wrong in a way that is hard to place but immediately noticeable. It is genuinely more jarring than having every bulb at slightly the wrong temperature. Different rooms can differ, and a kitchen at 3000K next to a living room at 2700K is fine, but keep each space internally consistent.

Light bulb FAQ

How many lumens do I need to replace a 60 watt bulb?

Eight hundred. The full set: a 40 watt incandescent is roughly 450 lumens, a 60 watt is 800, a 75 watt is 1100 and a 100 watt is 1600. In LED terms those are about 5, 9, 12 and 14 watts. Buy by the lumen figure rather than the watt equivalent printed on the front of the box, since those equivalence claims vary between manufacturers and the lumens do not.

What is the difference between soft white, warm white and bright white?

Soft white and warm white are usually the same thing, 2700K to 3000K. Bright white is the confusing one: it sits around 3500 to 4100K, which is neutral rather than either warm or cool, and the name implies brightness it has nothing to do with. Amazon sorts bulbs into four bands rather than the usual two, at Warm 2000 to 3499K, Neutral 3500 to 4099K, Cool 4100 to 4999K and Daylight 5000K and above, which is a more useful way to think about it than the soft white versus daylight framing.

Why does my LED bulb keep failing early?

Usually heat, and usually an enclosed fitting. LEDs run cool at the surface but the driver inside generates heat that needs somewhere to go, and a sealed glass shade traps it. Manufacturers state this plainly: many bulbs are explicitly not recommended for fully enclosed fixtures because heat buildup shortens life. If your fitting is sealed, buy a bulb specifically rated as enclosed-fixture safe.

Is high CRI worth paying for?

In kitchens, bathrooms and any room where you look at people, yes, and the price difference is small. Elsewhere, CRI 80 is genuinely fine. A hallway, a garage or a cupboard does not need accurate colour rendering, and buying 90 for the whole house is spending money where it will not be noticed. Put the good bulbs where you cook and where you look in a mirror.

Do dimmable bulbs cost more to run?

No, and dimming reduces consumption rather than increasing it. What dimmable bulbs need is a compatible dimmer: older switches were designed for incandescent loads and expect far more wattage than an LED draws, which is why they stutter or buzz at the low end. If you are fitting LEDs to an old dimmer, replacing the dimmer usually solves more than replacing the bulbs.

What about smart bulbs that change colour temperature?

They solve the choice by removing it, which is genuinely useful in a room used for different things at different times, such as a kitchen that is also a homework table. Two things to check before buying: the CRI, which is often lower on colour-changing bulbs because the same LEDs have to cover a wide range, and whether they dim at the bulb, which means you can leave an existing plain switch in place with no rewiring.

Do the same numbers work for Christmas lights?

For colour, yes: a warm white string sits at the warm end of the scale, like a soft white bulb, so check the box for a kelvin figure if you want the tree to match your lamps. Brightness works differently, because a tree is lit by hundreds of tiny bulbs rather than one. How many it needs depends on its width as well as its height, which I worked out in How Many Lights for a Christmas Tree?

The light bulb cheat sheet

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The Weekly Home Reset Checklist

Good light shows a room as it actually is, which is an argument for keeping it in reasonable order. This printable is a short weekly loop that keeps a minimal home actually minimal, without turning tidying into a project.

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Three numbers, and most guides mention one

Soft white against daylight is presented as a choice between two products, and it is really one of three numbers on a box that nobody reads together. Colour temperature in kelvin decides whether the light reads warm or cold. Lumens decide how much of it there is. And the colour rendering index decides whether the things it falls on look like themselves.

Choosing on kelvin alone is why people end up with a room that is the right colour and somehow still wrong. A warm bulb at too few lumens is gloomy rather than cosy. A high lumen daylight bulb with poor rendering makes a warm room look grey and makes skin look ill.

So read all three, and match them to the job rather than to the room name. Kitchens and bathrooms want higher kelvin and high rendering because you are looking closely at things. Living rooms and bedrooms want lower kelvin, and rendering still matters there because it is where your textiles and wood live.

Buy one bulb before you buy eight. A box is cheap and a whole house of the wrong light is not. And remember the shade around it: a linen drum softens even a slightly cool bulb, while a bare or oversized shade exposes every flaw. If you’re replacing one, here is how to measure a lamp shade so it actually fits.