Scrape off any excess ketchup with a dull knife or spoon
Rinse the stain from the back of the fabric with cold water
Apply liquid laundry detergent or stain remover directly to the stain
Gently rub the fabric together or use a soft brush
Let it sit for 5 to 10 minutes
Rinse again with cold water
Repeat if needed until the stain fades
Wash the clothing in the coldest water safe for the fabric
Check the stain before drying
Air-dry the item if the stain remains
Repeat the treatment before using a dryer if needed