How many watts to a lumen?

Question

hand held torch has 80 lumens output wondered what ratio to watts electric that is?

Answer 1

I have no idea. But this may help if you understand this thing.

http://en.wikipedia.org/wiki/Photometry_...

Answer 2

ask the CIBSE, they have all the Lumen outputs on all lamps

Answer 3

There is no direct conversion possible, they are different units.

you are looking for efficiency of the light, and they vary from 10% to 50%.

.

Answer 4

Go to ask.com and search lumens and calculating lumens and watts there.....I got a ton of hits, but I'm a math dolt, so I wouldn't want to try to do the calculation for you.  It appears there are formulas to figure this out.  Have fun.

Answer 5

I don't believe there is a direct connection between Watts and lumen. Watts are a measurement of power where as Lumen's are a measurement of light output. A good example to use is looking at a typical low energy light, one of these may run at 15watts but gives the same lumen output as a standard light bulb that runs at 60watts. Both give equivalent lumen output but use different amounts of power to produce it. I'm sorry but I don't know the technical terms to explain all this but that's basically how it is

Answer 6

Wattage is not necessarily related to lumens. Different light emitting devices have different efficiencies and so there is not a direct relationship. LEDs, Halogens, fluoros, normal filament bulbs.

Answer 7

You can't convert directly between them. They are measuring completly different things.

Lumens measure the flux of a light being produced by a light source or received by a surface.

Watts measure the amount of power used.

Answer 8

The lumens to watts ratio will depend on the type of lightbulb.  In general the larger the bulb, the ligher the lumens to watts ratio.  

Here are a few ranges I found for various types of lighting.

Incandescent* = 12 to 20 lumens per watt

Halogen = 12 to 15 lumens per watt

Mercury Vapor = 48 to 56 lumens per watt

High Pressure Sodium = 80 to 130 lumens per watt

Sorry I don't have any data for LED's or CFL's.

Some bulbs will have a reduced lumens per watt output over their lifetime.  (i.e.  They get dimmer with age)

*Really small incandescent bulbs are in the range of 7 to 10 lumens per watt.  Assuming your torch uses an incandescent bulb, I would the 80 lumens output to be around 10 watts.

Answer 9

*They are different.

*he lumen (symbol: lm) is the SI unit of luminous flux,

a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. The lumen is defined in relation to the candela by

    1 lm = 1 cd·sr = 1 lx·m2

That is, a light source that uniformly radiates one candela in all directions radiates a total of 4π lumens. If the source were partially covered by an ideal absorbing hemisphere, that system would radiate half as much luminous flux—only 2π lumens.

*If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, its total luminous flux emitted into that angle is one lumen. Alternatively, an isotropic one-candela light source emits a total luminous flux of exactly 4π lumens. The lumen can be thought of casually as a measure of the total "amount" of visible light in some defined beam or angle, or emitted from some source.

A standard North American 100 watt incandescent light bulb emits 1500–1700 lumens,while a standard European 230 V model emits 1200–1400 lm.

A 100 watt high-pressure sodium vapor lamp emits around 15,000 lumens.

*The watt (symbol: W) is the SI derived unit of power, equal to one joule of energy per second. It measures a rate of energy use or production..