Free Lumens to Watts calculator
Lumens measure brightness; watts measure power. Enter a bulb's lumens and pick its type — incandescent, halogen, CFL or LED — to see the wattage it draws, or switch direction to go from watts to lumens, updated live, as you type.
On this page15 sections
Estimates based on typical luminous efficacy. Check the lm/W on your bulb's box for an exact figure.
Results are estimates. Consult a professional.
How the lumens to watts calculator works
Lumens measure how much light a bulb gives off; watts measure how much electricity it draws. The link between them is luminous efficacy — the lumens a bulb produces for each watt it uses, written lm/W. This lumens to watts calculator divides your lumens by the efficacy of the bulb type you pick, so you see the wattage that produces that brightness. Flip the direction and it multiplies watts by efficacy to give you lumens.
Lumens vs. watts: what each one measures
For decades people bought bulbs by watts because, with incandescent bulbs, wattage tracked brightness closely. A 60-watt bulb was always about as bright as the next 60-watt bulb. Then LEDs arrived and broke that habit: a 9-watt LED can match a 60-watt incandescent. Watts no longer tell you how bright a bulb is — they only tell you how much power it pulls.
Lumens — the brightness number
Lumens are the unit of light output. More lumens means a brighter bulb. A typical 60-watt incandescent replacement is rated around 800 lumens; a bright kitchen bulb might be 1,600. When two bulbs claim the same lumens, they look equally bright, whatever their wattage.
Watts — the energy number
Watts measure the rate a bulb burns electricity, which drives your running cost. Lower watts for the same lumens means a more efficient bulb and a smaller bill. That is the whole case for LEDs: they deliver the lumens you want at a fraction of the watts.
A worked example: converting 800 lumens to watts
Maria wants a bulb as bright as her old living-room lamp — about 800 lumens. She wants to know the wattage on an old-style incandescent versus a modern LED, so she can see the energy she would save by switching.
Step 1 — Watts on an incandescent bulb
Incandescent efficacy is about 15 lm/W. So 800 ÷ 15 = 53.3 watts. That is why old 800-lumen bulbs were sold around the 60-watt mark.
Step 2 — Watts on an LED
LED efficacy is about 90 lm/W. So 800 ÷ 90 = 8.9 watts. The same 800 lumens of light, for roughly one-sixth of the power.
Step 3 — Read the saving
Switching the bulb cuts the draw from 53.3 W to 8.9 W — about 44 watts saved per bulb, for the same brightness. Across a house full of bulbs running several hours a day, that is a visible drop on the electricity bill.
Lumens to watts conversion chart by bulb type
This chart applies the calculator's efficacy figures to common lumen levels. Read across a row to compare the watts each bulb technology needs for the same brightness. The gap between the incandescent and LED columns is the energy you save by switching.
| Lumens | Incandescent (15 lm/W) | Halogen (20 lm/W) | CFL (60 lm/W) | LED (90 lm/W) |
|---|---|---|---|---|
| 450 lm | 30.0 W | 22.5 W | 7.5 W | 5.0 W |
| 800 lm | 53.3 W | 40.0 W | 13.3 W | 8.9 W |
| 1,100 lm | 73.3 W | 55.0 W | 18.3 W | 12.2 W |
| 1,600 lm | 106.7 W | 80.0 W | 26.7 W | 17.8 W |
| 2,600 lm | 173.3 W | 130.0 W | 43.3 W | 28.9 W |
Each cell is lumens ÷ the efficacy in its column header. These are constant-efficacy figures, the same math the calculator runs. Real bulbs vary by a watt or two with model and quality.
Efficacy is a range, not a fixed point. Budget LEDs sit near 80 lm/W; premium ones reach 100 or more. Use the custom efficacy field if your bulb's box lists a lumens-per-watt figure, and the calculator will use it instead of the typical value.
The classic lumen equivalence table (rated replacements)
When stores label an LED "60-watt equivalent," they are using the rated-replacement convention below, not pure efficacy math. It maps the old incandescent wattage everyone remembers to the lumens that bulb produced, then to the LED wattage that matches it. This is the table on the back of most bulb boxes.
| Incandescent "equivalent" | Brightness (lumens) | LED watts |
|---|---|---|
| 40 W | ~450 lm | 4–5 W |
| 60 W | ~800 lm | 8–9 W |
| 75 W | ~1,100 lm | 9–13 W |
| 100 W | ~1,600 lm | 16–18 W |
| 150 W | ~2,600 lm | 25–28 W |
Source: ENERGY STAR / FTC Lighting Facts replacement guidance. The incandescent column is historical bulb wattage, not a calculator output.
Notice this table implies a changing efficacy: 450 ÷ 40 = 11.3 lm/W, but 1,600 ÷ 100 = 16 lm/W. No single number reproduces it, because the wattages are the ones bulbs were sold at over the years — not the result of dividing by one efficacy. That is why a "60 W ≈ 800 lm" row sits next to the calculator's 53.3 W: same idea, two different conventions. For an exact, source-by-source figure, use the calculator above with the efficacy your bulb lists.
How many watts is 800, 1,000 or 1,500 lumens?
The answer depends entirely on the bulb type, because watts follow efficacy. Here are the conversions people ask for most, given for an LED — the bulb most buyers are choosing today.
- 800 lumens is about 8.9 W of LED (800 ÷ 90) — the standard 60-watt-equivalent bulb.
- 1,000 lumens is about 11.1 W of LED (1,000 ÷ 90) — a bright, general-purpose bulb.
- 1,500 lumens is about 16.7 W of LED (1,500 ÷ 90) — close to an old 100-watt bulb.
- Going the other way, a 10 W LED at 90 lm/W puts out about 900 lumens.
For an incandescent, divide by 15 instead of 90, and the watts jump roughly six-fold for the same lumens. That multiplier — six times the power for the same light — is the simplest way to picture why LEDs took over.
How to use lumens when shopping for bulbs
The label tells you everything once you know where to look. The Lighting Facts panel, required on bulb packaging, lists brightness in lumens first — that is the number to match, not the watts. Here is how to turn that into a confident purchase.
- Match the lumens, not the watts. Replacing a 60-watt incandescent? Look for roughly 800 lumens, whatever the new bulb's wattage.
- Use the room as a guide. Bedrooms and living rooms feel right around 450–800 lumens per bulb; kitchens and work areas want 800–1,600.
- Check the watts for cost. Once two bulbs match on lumens, the lower-wattage one is cheaper to run — that is your efficiency winner.
- Mind colour, not just brightness. Lumens set how bright; the Kelvin number sets how warm or cool the light looks. They are separate choices.
- Confirm the efficacy if it's listed. Premium LEDs print lm/W on the box; drop it into the custom field for an exact watts figure.
Working out lighting for a whole room or yard? Pair this with the square footage calculator to size the space, then total the lumens you need across the bulbs that will fill it.
Why an LED needs so few watts for the same light
An incandescent bulb makes light by heating a wire until it glows. Most of the energy leaves as heat, not light — only a small slice becomes the brightness you wanted. That is why its efficacy is so low, around 15 lm/W, and why the bulb is hot to touch.
An LED makes light electronically, with very little waste heat, so far more of each watt turns into lumens — about 90 lm/W, six times an incandescent. Same lumens, one-sixth the watts. Halogens (about 20 lm/W) are slightly better incandescents; CFLs (about 60 lm/W) sit in between, which is why a CFL needs roughly a quarter of the incandescent watts and an LED even fewer.
Lighting terms, defined
How accurate is this lumens to watts calculator?
The arithmetic is exact: lumens divided by efficacy is the precise wattage for the efficacy you give it, and the reverse multiplication is exact too. If you enter the lm/W printed on your bulb's box, the watts figure is as accurate as that rating.
The defaults are typical figures, and real bulbs vary. LED efficacy spans roughly 80 to 100 lm/W depending on brand and quality, so a result built on the 90 lm/W default can drift a watt or two from a specific bulb. Treat the bulb-type presets as planning numbers, use the custom efficacy field when your packaging lists lm/W, and remember the separate rated-replacement table reflects historical bulb wattages rather than constant-efficacy math.
Frequently asked questions about the free Lumens to Watts calculator
About this Lumens to Watts calculator
This Lumens to Watts calculator runs entirely in your browser — nothing you type is sent anywhere. It converts between brightness (lumens) and power (watts) using the typical luminous efficacy of each bulb type, and reports the LED-equivalent wattage so you can see the energy saved by switching.
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