Laundry detergents contain surfactants that attach to oil, dirt, food and other stains to remove them from clothing. Detergents may also contain enzymes, fragrance and other ingredients to help brighten whites and colors and make the clothing smell fresher.
More concentrated versions of detergents help lessen the amount of detergent introduced into the water system and reduce the size of the packaging needed to hold the detergent. When adding detergent to the washing machine, consider the size of the load, whether the machine is a high efficiency machine, how soiled the clothes are, what temperature water is being used and whether the water is hard or soft.
If an average person washes four medium loads of laundry each week in a regular top-loading washer, he will use 6.25 fluid oz. of detergent each week. That adds up to 25 fluid oz. each month, or half of a 50 oz. bottle of detergent.