Watts to Lumens Calculator
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Watts and lumens
Most of us are familiar with the power ratings associated with lightbulbs measured in watts (25 watts, 40 watts and 100 watts are common examples). The watt is a unit of power. By contrast, the lumen is a unit of brightness, a measure of the total quantity of visible light emitted by a light source.
Lumens versus watts
Modern energy-efficient bulbs use much less power (wattage) when compared to their incandescent and fluorescent counterparts. As low-wattage bulbs become more commonplace, we need a better way of measuring their output. This is where the lumen comes in. Figures for lumens appear on the packaging of all light bulbs and allow us to compare the brightness (or dimness) of a bulb.
Let's imagine that you are looking for an extremely bright bulb that emits 1,300 lumens. For an LED bulb, producing 1,300 lumens will require around 15 watts of power. However, for a less-efficient halogen bulb, over 60 watts of power are likely to be required to produce the same brightness. Same level of brightness, different amount of power required to produce it.
As you'll see from this example, if you're looking to replace your old incandescent or halogen bulbs with more energy-efficient ones (CFL, LED), being able to cross-reference lumen figures will help you pick the right bulb.
Converting watts to lumens
Converting watts to lumens requires the following formula:
How many lumens do I need?
More lumens means more light. So, if you previously bought incandescent bulbs measured in watts, here's a handy guide showing how many lumens you might need and the wattage conversion. Note that these conversions use a set average figure for lumens per watt (lm/W), based upon data from the Energy Saving Trust and Energy Star. Actual light efficiency and output will vary by product. So, you're recommended to check the 'lighting facts' label on the bulb packaging before purchase.
| Incandescent bulb (12-18 lm/W) |
Lumens (lm) |
LED bulb (90 lm/W) |
Halogen (23 lm/W) |
|---|---|---|---|
| 25 W | 300-450 lm | 3-5 W | 15-22 W |
| 40 W | 480-720 lm | 5-8 W | 23-35W |
| 60 W | 720-1080 lm | 8-12 W | 35-52 W |
| 75 W | 900-1350 lm | 10-15 W | 44-65 W |
| 100 W | 1200-1800 lm | 14-20 W | 58-87 W |
| Conversions are a guide only. Bulb efficiency may vary. | |||
If you're considering replacing your existing light bulbs with more energy-effiicient LED bulbs, take a look at our LED Savings Calculator to see the possible savings.
If you have any problems using our watts to lumens converter, please contact us.