goten said:
I tried many times to weigh four bags of each on my bathroom scale, but it's too coarse to get a solid reading.
You need to find a scale with a fine degree of precision at the largest weight you can use it to measure. A bathroom scale you can read to the pound on say, a ~45 lb case, has a precision of 1/45 (0.0222), about 2%. A digital fish scale that reads up to 10 lbs by the ounce (160oz) ha a precision of 1/160 (0.00625), about 0.6% which is better than the bathroom scale. Note that if you had two cases available to weigh on the bathroom scale, you'd have 1/90 (.0111), improving precision to about 1%, though still not as good as the fish scale. So that's why it's important to use as much of a scale's range as possible. If you hang a bag of diapers on the fish scale and are only getting a reading around 5lbs (80oz), you're using 1/80 (0.0125), slightly worse precision than the bathroom scale at two cases. So a more coarse scale can sometimes give a better reading if used properly.
You can ignore the division and percentages for simplicity... just find a way to get the biggest reading possible, the most pounds or the most ounces or most grams or whatever unit your scale supports. The bigger the number is before you divide by the number of diapers you put on the scale, the higher quality the measurement will be.
To that end, I set a light platform on top of a digital kitchen scale and zero it, and then stack single diapers on that until just before it overloads, then divide the reading by the number of diapers, to get the most precision reading possible from that scale. This method is a lot more precise than trying to weigh just one diaper on the same scale, and also averages out some of the minor variation between diapers.
Doin' Science!