Step 2: Measure the inside of the frame in the back of the chair, this one measures 21.5" wide.
Step 3: Take both the measurements which is 23", you would order a 23" wide seat cushion.
Step 4: Take the measurement of the depth of the chair, from the front rail to the back, add 1". This on measures 23" deep, so you would order a 24" deep cushion.
Step 5: Measure from the floor to the top of the deck. The ideal seating height is 18 to19". This one measures 12 1/2" high, therefore we would order a 6" thick cushion to make the top of the cushion 18 1/2" off the ground.
You would order a 23" wide in front x 23" wide in back x 24" deep, x 6" thick seat cushion.
Step 6: Measure the width of the chair back. This one measures 23" wide, so you would order a 23" wide back cushion. Usually the seat and back cushions are the same width.
Step 7: Measure the height of the back from the top of the deck to the top of the chair, then take off the seat thickness. This one measures 25" high. Deduct the thickness of your seat cushion from the total height to determine the back height. You would order a 19" high back cushion. It's also good to measure the back of your old cushions. It's OK if the back cushion extends over the the frame. The average size is 19" - 20" high anything lower than 18" is uncomfortable.
Step 8: If your seat depth is 22" or under order a 4" thick back cushion with buttons. If your seat depth is 23" or over order a 6" thick back cushion without buttons.
Step 9: Does your chair back curve on the top or go straight across? You have the option of either style. This one has a curved top, so you would order a curved top.
You would order a 23" wide x 19" high x 6" thick back cushion with a curved top.
Remember to measure twice and call if you have any questions!