Lumens to Watts Converter
Convert lumens to watts for any bulb type, and find the wattage to shop for.
What this tool does
A lumens to watts converter divides lumens by the luminous efficacy of the bulb type: LED bulbs produce 70 to 120 lumens per watt, CFLs about 60, and incandescent bulbs about 15. Replacing a 60 W incandescent needs about 800 lumens, which is only 7 to 10 W of LED. Wattage stopped predicting brightness when LEDs arrived - the lumen figure is the one that matters, and this converter translates between the two.
Converts lumens to watts for any luminous efficacy, including LED, CFL and incandescent.
Works backwards from a target brightness to the wattage to shop for.
Explains that wattage stopped predicting brightness once LEDs arrived.
Covers the common bulb-replacement steps from 40 W through 150 W equivalents.
How to use it
- Choose the bulb type: LED, CFL or incandescent.
- Enter either the lumens you need or the watts you have.
- The other field updates automatically.
- Read the replacement wattage and the running cost context.
- Match the lumen figure, not the old wattage, when shopping.
Why use this calculator
Converting lumens to watts is the translation everyone needs when replacing bulbs, because packaging shows both and old habits reach for watts. A 60 W incandescent produces about 800 lumens; an LED producing the same 800 lumens draws 8 W. Buying by wattage alone either buys too dim an LED or pays for far too much light. The lumen figure is the brightness; the wattage is only what it costs to produce.
Why we built it
We built the lumens to watts converter to show efficacy explicitly, because that ratio is the entire difference between bulb technologies. The appliance cost calculator puts a price on the running hours, the electricity unit price calculator works the rate, and the energy consumption calculator derives the yearly kWh from wattage and hours.
For the supply side of the fitting, the watts to amps converter handles the current draw, and the kWh to watts converter works back from a bill.
Who this tool is for
- Anyone replacing incandescent or halogen bulbs with LEDs
- Shoppers comparing bulb packaging across technologies
- Facilities managers planning a lighting upgrade
- Anyone checking whether a fixture's wattage rating is exceeded
When to use it
- Buying a replacement bulb and reading old watts on the box.
- Upgrading a room to LED and sizing the brightness.
- Checking a fitting's maximum wattage rating against a new bulb.
- Estimating the saving from a lighting change.
How it is calculated
Watts = lumens ÷ efficacy. Efficacy in lumens per watt differs by technology: incandescent about 15, halogen about 18, CFL about 60, LED 70 to 120. The reverse divides lumens by watts to find the efficacy of an unknown bulb. Running cost then follows from wattage × hours × rate.
Worked example: an 800-lumen replacement. As incandescent that is 800 ÷ 15 = 53 W (a 60 W bulb). As LED at 100 lm/W it is 8 W. Running 3 hours a day for a year, the difference between the two is roughly 155 kWh - about 20 a year at 0.13 per kWh.
The fitting's maximum-wattage rating is a heat limit, not a power supply limit. Exceeding it overheats the socket. LED bulbs draw far less, so an LED replacement is always under the old rating - but check the fitting is rated for LED enclosed fixtures if it is covered.
Brightness equivalents
| Brightness | Incandescent | Halogen | CFL | LED |
|---|---|---|---|---|
| 450 lm | 40 W | 35 W | 9 W | 5 – 7 W |
| 800 lm | 60 W | 50 W | 13 W | 8 – 10 W |
| 1,100 lm | 75 W | 70 W | 18 W | 11 – 13 W |
| 1,600 lm | 100 W | 90 W | 23 W | 15 – 18 W |
| 2,600 lm | 150 W | 120 W | 38 W | 24 – 30 W |
LED efficacy keeps improving, so a modern LED often beats the bottom of its range. Buy for the lumen figure; the wattage on the box is a consequence, not a specification.
A worked example
These are the values the calculator opens with, so you can see exactly what it does with them. Change any value on the page and the result updates; the figures below come from the same calculation.
| Input | Value |
|---|---|
| Lumens | 800 |
| Bulb type | LED |
With those inputs, the calculator returns:
- LED watts: about 8 to 10 W
- Incandescent equivalent: about 53 W
- Efficacy: about 100 lm/W
- Running cost saving vs incandescent: about 20 a year at 3 hours a day
What you enter, and what you get back
| Item | Details |
|---|---|
| Lumens or watts | Either one drives the conversion. |
| Bulb type | Sets the efficacy: LED, CFL or incandescent. |
| Result | Wattage, efficacy, equivalent technologies and running-cost context. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| LED seems too dim for its watts | Compared against old wattage expectations. | Compare the lumen figure, not the watts. |
| Fixture buzzes or dims | Old dimmer not rated for LED load. | Check the dimmer is LED-compatible. |
| Colour looks wrong | Kelvin temperature ignored. | Match the colour temperature as well as lumens. |
| Enclosed fitting overheats | Bulb not rated for enclosed fixtures. | Use an LED marked for enclosed use. |
Assumptions and limitations
- Efficacy figures are typical ranges; individual bulbs vary by model and manufacturer.
- Does not account for lumens lost to fittings, diffusers or dirt.
- Colour temperature and colour rendering are separate from brightness.
- Running-cost figures need your actual electricity rate to be exact.
Frequently asked questions
How do I convert lumens to watts?
Divide lumens by the efficacy of the bulb type. LED bulbs produce 70 to 120 lumens per watt, so 800 lumens needs about 8 to 10 W of LED; incandescent needs about 15 lm/W, so the same brightness takes roughly 53 W.
How many watts is 800 lumens?
About 8 to 10 W for an LED, 13 W for a CFL, or 53 to 60 W for an incandescent. 800 lumens is the standard '60 W equivalent' - the brightness stayed the same while the wattage collapsed.
What is luminous efficacy?
The ratio of lumens produced to watts consumed, written in lumens per watt (lm/W). It measures how efficiently a bulb turns electricity into visible light: incandescent about 15, CFL about 60, LED 70 to 120. Higher efficacy means more light for the same running cost.
How many lumens does a 60 watt bulb give?
An incandescent 60 W bulb produces about 800 lumens. That lumen figure is the benchmark for a standard room bulb, and the number to match when buying an LED replacement - the LED will draw only 8 to 10 W.
How do I choose a replacement LED bulb?
Match the lumens, not the watts: find the old bulb's lumen figure on its box or in its specification, then buy an LED producing the same lumens. Also match the fitting type and the colour temperature. The wattage of the LED is then simply what it costs to produce that light.
How do I convert watts to lumens?
Multiply watts by the efficacy. A 10 W LED at 100 lm/W produces 1,000 lumens; a 60 W incandescent at 15 lm/W produces about 900. The calculator runs this direction when you know the wattage and want the brightness.