What is lumen?
Lumen is the measure unit for the total quality of visible light emitted during a unit of time. The lumen indicates the brightness level of the light produced by the light source. Traditionally, electricians use foot-candle as the measure to tell the light intensity, as is the customary unit used in the United States. A foot-candle equals one lumen per square foot. The brightness level roughly equals to the light that is one foot away from a common wax candle.
If you need brighter LED strip lights, you will select strip light that is marked with higher value of lumens per unit length. Please be careful that different manufacturers may use different brightness marks.