Thanks to Michelle for this Frugal Baby Tip!
I only use 1/4 cup of grated soap per load. I grate 3 bars of Sunlight laundry soap (130 gm bars) at a time and store it in a plastic canister. I get about 18-20 loads out of that. So that would be around 6 per bar. I used to use 1/4 cup of Dr. Bronner's peppermint until I realized how much it was costing me!