Figure of Merit is a calculation that uses measured cell internal resistance and normalizes it to cell capacity. It is very useful when comparing packs of different sizes and from different manufacturers. The larger the calculated FOM, the better.

The meaning is as below, taking into account that a FOM=1 means a 30C Cell (able to deliver 30C based on it's internal cell witrh the highest IR.

• FOM < 1: below average < 30C capable
• FOM == 1: average - 30C capable
• FOM > 1: good - More than 30C capable
• FOM >> 1: outstanding - much more than 30C capable

Example calculator is here.
For more background information on FOM, go here: RC Groups Forum

Example calculation of FOM and its meaning from the rc-forum:

I calc C this way, C=370mV/capacity/IR, where 370mV is 1/10 of a lipo
 cell's nominal voltage. 

as an example my Turnigy 6S5000 has an IR of 2.4mohms/cell.
so it's C=370/5/2.4=30.8C.

or, 370000/5000/2.4=30.8

divide left & right by 30.8, 

that's exactly 12000/5000/2.4=1. 

It means a FOM=1 cell IS a 30C cell. a FOM=0.5 cell is a 15C cell....