Note: I have made a second version of this Powder Measuring Cup. The new version is lighter, has thinner walls, and can be printed without supports. You can find it here: https://makerworld.com/en/models/771239#profileId-707361 

According to Ariel laundry powder packaging, they recommends using 100ml/3,4 oz for every standard wash. This cup should help you with getting that amount consistently and not wasting too much while looking like a normal measuring cup.