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How do I know how bright a lamp is?


How bright is 5 watts? How bright is 300 lumen? Modern lamps require less electricity to provide the same light output compared to traditional bulbs. Therefore lumens are the decisive value for the brightness of a bulb. Lumen (abbreviated to lm) is the unit of measurement of the luminous flux, i.e. the amount of light that a lamp emits.


As a general rule of thumb:

Multiply the output of the old bulbs in watts by 10 and you will get an approximate lumen value.


Lumen at omnidirectional spotlights

The unit 'lumen' (lm) specified on the packaging indicates the luminous flux delivered by the bulb. The lumens provide a much better indicator of the brightness you can expect than the power consumption in watts (W).


Lumen at reflector lamps

  • All reflector lamps with a beam angle of up to 90° are prescribed with luminous flux in a 90° angle and can therefore be compared. The brightness is measured outside of the 90° angle even though the actual beam angle is lesser. 
  • All reflector lamps with a beam angle of 91° to up to 120° are prescribed with luminous flux in a 120° angle. These bulbs are not suitable for accent lighting. 
  • All bulbs with at beam angle greater than 120° are considered „non-directional light“ are prescribed with the luminous flux value (lumen, lm) that is determined in the complete 360° around the bulb.

The various units of measurement lumen (lm), lumen in the 90° angle (lm90°) and lumen in the 120° angle (lm120°) cannot be compared with each other.