I saw this tip years ago and have used it ever since. See my laundry cabinet above my washing machine? I buy big bottles of laundry detergent from Sam's Club and position them directly over the washer.
Then, when it's time to do the laundry, I don't even have to measure it out. I just pump is straight into the machine. I filled the cup once a long time ago to the desired level while counting. So now I just count to three as I pump, and I figure it's about right.
Hope this tip saves you time in the laundry room!