Both the dial and vernier calipers are almost always configured to permit inside as well as outside measurements. In addition, while dial-equipped slide calipers can be read directly for both outside and inside measurements, on those with a vernier scale.
Scale account has to be taken of the width of the â€śnibsâ€?used for inside measurements. This dimension has to be subtracted from the final reading to obtain the true dimension of the hole. (Note, too, that the width of the nibs sets a lower limit to the diameter of gap they can enter. )