Lumens vs Watts: How to Compare LED Bulbs Before You Buy

The short version: When you replace an old bulb, don’t just match the wattage. LED bulbs give useful light with far less power, so “more watts, more light” no longer works. Compare lumens first, then check that the bulb fits your fitting, suits the look you want, and can be dimmed if you need that.

Three things to remember

• Start with lumens. They tell you how much light you’ll actually get. Watts only tell you how much power the bulb uses.
• Check the fit before you order. Match the base, compare the bulb’s size with your shade, and remember that bulbs can’t be returned or exchanged.
• Don’t assume it dims. Only choose a dimmable bulb if the listing says so, and check it suits your dimmer.

What’s the difference between lumens and watts?

Lumens measure how much visible light a bulb produces. Watts measure how much electrical power it uses. When you’re choosing brightness, lumens are the number to compare, so check a listing’s product details for its lumen figure.

Here are two real examples from our bulbs range:

The filament bulb is listed as a replacement for a 40W bulb and gives 400 lumens. The opal bulb gives 810. Those lumen figures, not the old wattage habit, tell you which one will give enough light for the job. Always use the actual figures on the product listing.

Why does the same brightness look different in a room?

A bulb’s output is only part of the result, because where the light goes matters too. A shaded table lamp, an exposed decorative bulb, and a directional spotlight all spread light differently. A dark shade sends most of the light up and down, while a clear bulb feels much more exposed.

Your room matters as well. Pale walls and ceilings make a space feel brighter than dark ones under the same fitting. So think about where you need the light: the whole room, a book, a work surface, or one object. Don’t choose every bulb from a single brightness number.

How do you choose a colour temperature?

Colour temperature is measured in kelvin (K) and describes how warm or cool the white light looks. It’s a separate choice from brightness: a warm-looking bulb isn’t automatically dimmer, and a cool-looking one isn’t automatically stronger. Compare bulbs at the same lumens when you’re deciding which look you prefer.

As a guide, warm white (around 2700K to 3000K) gives a cosy glow for living spaces, while cooler white and daylight suit kitchens and task areas. In an open-plan room, decide which fittings will be used together, then keep their whites consistent or make the contrast deliberate. Mixed colours can look accidental, as we explain in our ceiling fans with lights guide.

How do you make sure a bulb fits your fitting?

• Base. Match the cap exactly, such as E27, E14, GU10, or B22. You can filter our bulbs by base.
• Size. Compare the bulb’s length and width with your shade or enclosed fitting. The opal bulb above is 108mm long, so a small shade may not suit it.
• Maximum wattage. Follow the fitting’s rating. For example, the Orb Glass Ceiling Light lists a maximum of 60W for its E27 bulb.
• Where it will be used. Check the bulb suits the fitting and the conditions. The opal bulb above is rated IP20, for indoor use.
• Beam. For directional bulbs, compare the beam angle as well as the lumens. Our GU10 spotlight bulb guide explains it.

One practical point: our listings state that no returns or exchanges are accepted on light bulbs, so check the base and size before you order.

Do you want to dim the light?

Check that the bulb is marked dimmable and that it suits your dimmer. Our bulb names end in “Dim” or “Non Dim,” and each listing has a Dimmable line. You can see why it matters in our own range: both bulbs above are LED, but the 9W opal is listed as dimmable while the 4W filament is not. So an LED label alone doesn’t tell you a bulb will dim.

With integrated LED fittings there’s no bulb to swap, so check the fitting’s own specification for a dimmable driver. If you’re unsure, ask the supplier or your installer which control to use, and try one bulb on the circuit before you buy several.

How do you build a shortlist?

Write down the fitting and its base, the space available, the output you want in lumens, your preferred white-light colour, and whether you need to dim. That gives you a much clearer comparison than choosing the biggest wattage or the most dramatic product photo.

Frequently asked questions

Do more watts mean a brighter LED bulb?
Generally yes, but not necessarily. Compare lumens instead. The same two 4W specified bulbs can deliver different lumens.

Can I use any LED bulb in my fitting?
Only if the base and size fit and the bulb stays within the fitting’s maximum wattage and suits the conditions. Check the listing’s base, dimensions, and rating.

Can I dim any LED bulb?
No. Choose a bulb listed as dimmable and check it suits your dimmer. Using a non-dimmable bulb on a dimmer can cause flickering or buzzing.

Can I return a light bulb?
No returns or exchanges are accepted on light bulbs, so confirm the fit first.

Are there bulbs that keep working during load shedding?
Yes. Our collection includes rechargeable LED bulbs in E27 and B22 that are listed as built to keep working through load shedding by switching to backup battery power.

Ready to compare? Explore bulbs at Lighting.co.za, read the listed specifications, and keep the packaging for future replacements. We deliver nationwide across South Africa.

Related guides: table lamp bulbs, floor lamp bulbs, GU10 spotlight bulbs, and track lighting bulbs.