B-DNA is the right-handed DNA helix that is the original model of DNA proposed by JD Watson and F Crick. In the B-DNA model, two DNA strands twist around each other spirally in a right-handed way with 10 base pairs per turn. The distance between the two base pairs (rise) is 0.34 nm.
The pitch is the distance measure for one complete turn of the helix that measured parallel to the axis. Therefore, the pitch of B-DNA is 3.4 nm. The pitch of A-DNA is 3.2 nm and the pitch for Z-DNA is 4.5 nm.