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Lumens vs Watts: What's the Difference?

Last updated: 2026-06-05

The Answer

Lumens measure brightness (the light you get); watts measure power consumption (the energy you use). With old incandescent bulbs the two were linked, so people shopped by watts. With LEDs that link is broken — a 10W LED and a 60W incandescent both produce about 800 lumens. Always choose a bulb by its lumens for brightness, and check watts only to compare running costs.

The Short Answer

For decades 'a 60-watt bulb' was shorthand for a certain brightness, because incandescent bulbs of a given wattage always produced roughly the same light. LEDs changed that: they create the same brightness from a fraction of the power. So watts no longer tell you how bright a bulb is — lumens do. Buy by lumens for the light you want, and treat low wattage as the bonus that lowers your bill.

The Full Explanation

The Conversion You Actually Need

Use lumens as your target: 450 lumens replaces an old 40W bulb, 800 lumens a 60W, 1,100 lumens a 75W, and 1,600 lumens a 100W. A modern LED hits those figures at roughly 5W, 8–10W, 11–13W and 14–18W respectively — and ultra-efficient models go lower still. So when a package says '60W equivalent', what matters is the lumen figure printed alongside it.

Why Watts Still Matter (a Bit)

Watts haven't become useless — they now tell you about efficiency and running cost rather than brightness. Between two bulbs of equal lumens, the lower-wattage one costs less to run. The measure that ties them together is efficacy (lumens per watt): basic LEDs deliver around 80–100 lm/W, while the most efficient A-rated bulbs exceed 150 lm/W. Higher efficacy means the same light for less money.

How to Shop in Practice

Decide how bright the space needs to be in lumens (e.g. a living room wants 1,500–3,000 lumens total across its fittings), then buy bulbs that add up to that figure. Ignore the big 'equivalent watt' marketing number and read the actual lumens. Only compare the real wattage when two bulbs match on lumens and colour, to see which is cheaper to run over time.

Related Questions

How many lumens do I need?Path lights need 100–200 lumens; living rooms 1,500–3,000; kitchens 3,000–5,000; security floods 1,500–3,000.Do LED lights save money?Yes. LEDs produce the same lumens as incandescent bulbs using 80–90% less wattage, saving £200–300 a year per home.What is CRI in lighting?Brightness isn't everything — CRI measures how accurately a bulb renders colour. Choose CRI 90+ for living spaces.

Sources

  1. 1
    Light Bulbs

    ENERGY STAR

  2. 2
    LED Lighting

    U.S. Department of Energy

  3. 3
    IES Standards

    Illuminating Engineering Society