Most brands instruct the consumer to "fill to line 1 for medium loads." Line 1 on this cap is about 1cm from the bottom, as shown in the photo below.
As well, when you put the cap back on the bottle, the cap and bottle are designed so that any residual detergent that remains in the cup drains back into the bottle.
I thought everyone knew that until the day I saw my wife pouring the detergent directly into the washing machine. Not only do you waste money using more detergent than you need to, the excess detergent produces lots of suds that muck up your drain pipe.
If you want to reduce your ecological footprint, this is one way to do it.
