The Volume Calculation uses the unchanged volume of the undriven and driven rivet to determine the original rivet lenth. The driven shop head should have a diameter of 1.5 * D (1.33 for thin sheet metal) and a height of 0.5 * D (0.66 for thin sheet metal).

The 1.5 * D Rule is an unprecise approximation and says the undriven rivet should stick out 1.5 * D after you placed it into the hole. The Volume Calculation is the preferred method.

The following explains the Volume Calculation:

(I) Volume of a cylinder:
V = 1/4 * D2 * Π * L
    where:
       D = diameter of the cyclinder
        L = length of the cylinder

(II) Volume (driven) = Volume (undriven, original):
1/4 * D2driven head * Π * Ldriven head + 1/4 * D2 * Π * (A + B) = 1/4 * D2 * Π * L
    where:
       Ddriven head = diameter of the driven head (upset dimension)
        Ldriven head = height of the driven head
        D = diameter of the rivet shaft
        L = original length of the undriven rivet

Rules for the upset dimensions:
(III) Ddriven head = 3/2 * D and (IV) Ldriven head = 1/2 * D

(III) and (IV) inserted into (II):
1/4 * 9/4 * D2 * Π * 1/2 * D + 1/4 * D2 * Π * (A + B) = 1/4 * D2 * Π * L =>
1/4 * D2 * Π * (9/8 * D + A + B) = 1/4 * D2 * Π * L =>
9/8 * D + A + B = L =>
L = 9/8 * D + A + B

For thin skinned aircraft with the 1.33/0.66 rule the resulting formula is:
L = 32/27 * D + A + B