How much elastic is in a king sheet?
This will depend on if you want elastic all the way around the sheet or just on the corners. I prefer to just add mine to the corners of the sheet because it makes them easier to fold. Other than this if you want it all the way around the sheet you need to find the total size of your sheet by taking the width and length and mulitpling them together. Now you have this measure you will divide it in half to find out how much elastic you need.
One way to adjust the size of too big fitted sheets is to take in the corner seams. Try this fix if your sheet is ill fitting.
Making your own bed sheets allows you to choose your fabric and perhaps get a better fit. This is a page about pattern for fitted queen sheets.
This is a page about making fitted crib sheets. Making your own fitted crib sheets allows you to have them coordinate with your child's room. They also are a thoughtful gift idea.