What are Lumens?
Lumens basically mean how bright a light source is. Lumens measure the brightness of not only flashlights, but also lightbulbs, candles, etc.
You might have also heard about Watts. Higher Watts however does not necessarily mean higher Lumens, as Watts only signify the power/energy usage of a light source.
How many Lumens do you need?
For Lumens you need in your house, here is a guide from: Integral LED
However, for flashlight and Lumens needed for the outdoors in darkness, here is a rough guide.
Up to 100 Lumens
You will be able to see your surroundings when you have a light source that goes up to 100 Lumens, but if you need to see farther into the distance and your path, then you need higher Lumens.
Usually 400-700 Lumens should be perfectly fine for most flashlights
Is “the brighter the better” necessarily true?
Depending on your environment and what you need it for, you should consider how many Lumens a flashlight has. Brighter does not necessarily mean, the better, because a flashlight can be too bright for your surroundings and ironically, it may prevent you seeing all too well.
For example: You wouldn’t use a spotlight to search around your house when the power goes out; it’s too BRIGHT! A pocket flashlight will work just fine in that case. However, when you are driving down the road, you obviously need something brighter with higher Lumens.