A normal thyroid is when the right lobe measures 5x1. 8 x 2. 0 cm. and the left lobe measures 4. 0 x1. 5x 1. 4cm. The usual way of measuring the thyroid is by having an ultra-sound. If one or both lobes are large you need a Fine Needle Aspiration. These are not always accurate, so some surgeons prefer to remove the thyroid.