I'm asking myself why I even measured these but I was curious at one point so maybe someone else will find this useful. I used pro baking measuring cups, 1 cup size leveled off, and a jewelry scale that goes to hundredths of an oz / tenths of a grams. It's far more exact/accurate than my kitchen scale. I recalibrated w/ calibration weights prior to weighing for accuracy. I'm out of powdered Tide so that's missing...
PER CUP:
-Ariel Ultra Oxi: 4.46oz / 126.5g
-Biz powder: 6.51oz / 184.5g
-OxiClean Versatile: 7.96oz / 225.7g
-Dishwashing Powder (Cascade): 7.47oz / 211.7g
(^has enzymes so a great whites/stain booster)
-Baking Soda: 8.13oz / 230.4g
-Borax (20 Mule Team): 5.71oz / 161.9g
-Washing Soda (Arm&Ham): 8.96oz / 254.1g
-Arēs Grime Release (a washing soda base detergent booster): 9.03oz / 255.9g
Box sizes:
-Arm & Hammer Washing Soda 55oz box = 6.14 cups
-20 Mule Team Borax 65oz box = 11.38 cups
I'm sure it's fine to round anything to the nearest 10th (ie 4.46oz becomes 4.5oz/cup or 8.13oz becomes 8oz/cup, etc).
Lastly some storage tips...if you can find the Arēs cheaply ($1 at my local bargain store in LA), once empty refill it w/ you borax or washing soda as it has 1oz raised increment marks in the plastic of the bottle that makes for ez measuring. Alternatively you can buy the Downy Concentrado bottles and use those for your borax or washing soda as they're really inexpensive. I believe they're the Mexican Downy line. At my local dollar/bargain store the 800ml (27.1 fl oz) is $1.69 and the 1.4L (47.3 fl oz) is $2.99. They have a screw cap that you can measure the powder with but they're small enough to fit in my laundry bag so I don't have to drag all my full size product boxes to my apt complex laundry room. Any small softener bottle w a screw on cup cap should work tho. My last rec is to use the Kraft Mallow Bits ($1.59 at Target) shaker bottles for various powders or detergents. They have a screw on dual flip top cap w/ shake and pour sides and are extremely versatile. Fits about 2 cups. Amazon sells 16oz and larger sizes too just search "spice bottle 32oz."