3 Measuring in a straight line is critical for all of these measurements. Butler stresses that this is not like being fitted for a driving suit. All the seat dimensions are on a flat plane, so if you allow your tape measure to bend like you see here, your seat will wind up way too large. In fact, Butler recommends that if you’re making your own measurements, use a yardstick, a framing square or some other rigid measuring tool. This will help ensure your measurements are as accurate as possible.