How Much Laundry Detergent to Use - The Spruce
For heavily-soiled clothes, presoak or spot treat stains with a bit of liquid detergent rather than add extra detergent to the entire load. Use 1/4 to 1/3 cup commercial powdered laundry detergent. Use 1/4 to 1/3 cup powdered homemade laundry detergent and 1/8 to 1/4 cup liquid homemade laundry detergent.