Determining the Width for Your CoolSeat To determine the width of your seat, you will want to measure along the back of the seat, parallel to the shoulder strap openings. Measure the back of the seat where it is flat, don't include any part of the seat that may start to curve around to the side bolsters. See the images below for further clarification. The proper way to measure the width for your CoolSeat.   This measurement is not parallel to the shoulder strap openings, which means your measurement will be too long and your CoolSeat will not fit.   This measurement travels onto the side bolsters, which means your measurement will be too long and your CoolSeat will not fit.