Bed sheets come in standard king, queen, full and single sizes, with each size having standard dimensions to fit mattresses neatly. If you have sheets that you with to alter to fit a smaller mattress, you can make a bed sheet smaller. Basic sewing skills will help you finish this project to transform a larger bed sheet into one that will fit your mattress securely.
Determine how much smaller you wish to make the fitted sheet. Measure the mattress, if necessary, and measure the sheet so you can subtract the difference to determine how much fabric to eliminate. Subtract 1 inch from the difference-- this is the amount of fabric to remove from the sheet. For example, if the mattress measures 54 inches and the fitted sheet measures 60 inches, 60 - 54 = 6. Subtract 6 - 1 = 5 -- you must eliminate 5 inches.
Mark a cutting line on the sheet that starts at the bottom edge about 20 inches from the right fitted corner and extends up to the top edge of the sheet. Mark a second cutting line from the bottom to the top of the sheet by measuring to the left of the first line the measurement you calculated (5 inches in the example). Extend the cutting line up to the top edge of the sheet. Cut along the cutting lines with the scissors.
Place the two pieces of the sheet together with the right sides of the fabric facing each other. Align the cut edges and the top and bottom edges precisely, and pin along the cut edges.
Stitch along the pinned edge using a 1/2-inch seam allowance. Remove the pins, and then press the seam open to finish making the fitted sheet smaller.
Determine how much smaller you wish to make the top sheet. Measure the mattress as well as the sheet so you can calculate how much fabric to eliminate. Subtract 1/2-inch from this measurement -- this is the amount of fabric to remove from the sheet. For example, if you wish to remove 10 inches from the top sheet, subtract 10 - 1/2 = 9 1/2 -- you must eliminate 9 1/2 inches from the top sheet.
Measure the distance you calculated from the right edge of the sheet, and mark a cutting line that starts at the bottom edge and extends up to the top edge of the sheet. Cut along the cutting line.
Fold under the cut edge 1/4-inch, and press the fold. Stitch along the fold, sewing 1/8-inch away from the fold. Fold under the fabric another 1/4-inch, and then press the fold again. Stitch along the fold a second time, again sewing 1/8-inch away from the fold.