400 lumens of light is given off by a 40 watt light bulb. 400 lumens is equal to 37.161216 foot-candles or 400 candelas. Since a candela is approximately equal to the light given off by 1 candle, 400 lumens gives off about the same amount of light as 400 candles combined.
A standard 4 watt night light gives off about 20 lumens, while a 25 watt light bulb gives off 180 lumens. A 60 watt light bulb gives off 800 lumens, while a 100 watt light bulb gives off 1,700 lumens.
A flashlight giving off 400 lumens is considered more than sufficient to be used by the police, firemen, or other emergency responders. Police flashlights commonly give off about 200 to 220 lumens.
With new lighting technologies such as CFLs and LEDs having much lower wattage ratings than the incandescent bulbs they are now replacing, it's important to learn your lumens!