To get the passanger/space ratio, divide the size of the ship, as measured by Gross Registered Tons, or GRT by the number of passangers. Both of these numbers should be readilly available. If you are comairing ships, make sure they used the same measure. You can use the double occupancy rate, or the total berths rate. Which one you use shouldn't matter much, just so ping as you are using the same measure.