How to determine the force of a solenoid based on inductance
Force calculation:

\$F=(N*I)^2\mu_0\dfrac{A}{(2g^2)}\$

Where:

\$\mu_0=4\pi*10^{-7}\$
\$F\$ is the force in Newtons
\$N\$ is the number of turns
\$I\$ is the current in Amps
\$A\$ is the area in length units squared
\$g\$ is the length of the gap between the solenoid and a piece of metal

From this calculator

Inductance calculation:

\$L=\dfrac{d^2*n^2}{18d+40l}\$

Where:

\$L\$ is inductance in micro Henrys
\$d\$ is coil diameter in inches
\$l\$ is coil length in inches
\$n\$ is number of turns.

From this calculator