Red is ANH landing gear. Blue is gear added by ESB
Scaling off a decent bottom view of the Falcon gives me dimensions of 137 x 133 cm for each landing gear, or about 1.821 m2 per landing gear, for a total "on ground" contact area of 12.747 m2.
Example Ground Pressures in are:
Human (16 PSI) 11,249 kg/m2
Threshold for Soft Ground Mobility (25 PSI) 17,577 kg/m2
Passenger Car (30 PSI) 21,092 kg/m2
Mountain Bike (40 PSI) 28,123 kg/m2
Motorized Cherry Picker Lift (150 PSI) 105,460 kg/m2
The thing about Star Wars mobility is that they don't play by "normal" rules due to the existence of repulsorlifts, which allow for easy vertical takeoffs, as shown by the Falcon repeatedly during the movies; so I would say that the Falcon could go as high as 50 PSI ground loading, because it doesn't have to "fight" the ground to start moving -- i.e. it doesn't have to overcome rolling resistance.
That being said, there are inherent limitations, because if you have too high a ground pressure, the Falcon sinks all the way to it's belly in muck; and the entrance ramp can't open.
At 50 PSI loading, the falcon's maximum mass for "unimproved planetary landings" is 448.1 metric tons.
Interestingly; in ANH, the Falcon had a different landing gear configuration; with just 5 landing gear legs arranged in a (1 x 1 forward) and (2 x 2 aft) configuration, for a total contact area of 9.105m2. At 50 PSI loading, that comes out to 320 metric tons.
If we hold the Falcon's landing mass constant at 320 metric tons; the ground pressure of the Falcon comes out to:
ANH: 49.98 PSI (35,145 kg/m2)
ESB: 35.7 PSI (25,103 kg/m2)
One possible reason for the difference is that before the events of A New Hope, Solo basically flew the Falcon out of spaceports, with the occasional side jaunt to impromptu landing strips that were carefully chosen for smuggling, whereas when he started working with the Rebellion after the events of A New Hope, he needed to go to places really off the beaten path with little prep time available; so he added the landing gear to reduce his ground pressure.
Yes, I know, you could always just use repulsorlifts to reduce your ground pressure, the technology is shown as being reliable enough for mid-air floating landing platforms in Attack of the Clones on Coruscant; but that would consume energy (bad for tramp freighters $$$) and create a energy signature much more detectable (bad for smugglers) if it had to be kept on all the time to keep the Falcon from collapsing/sinking into the ground under its own weight.
Doing some more refining on the falcon's volume:
**********
"Claws" -- Triangle 9 m long by 6 m wide and 1.25m thick (33.75m3 per claw, 67.5m3 for both)
***********
Saucer (1513.08 m3)
Top -- 5.8m top radius, 12m bottom radius, 1.83m long conical frustrum (473.80m3)
Middle -- 12m radius, 1.25m thick cylinder (565.48 m3)
Bottom
Bottom -- 5.8m top radius, 12m bottom radius, 1.83m long conical frustrum (473.80m3)
*******
Cockpit (49.87 m3)
1.86m radius and 3.4m long cylinder (36.95m3)
plus
0.77m top radius, 1.86m bottom radius, 2.25m long conical frustrum (12.92m3)
*********
Total Volume: 1,630.45 m3
Estimated Density at 50 PSI landing leg pressure (448.1 metric tons) in ESB configuration -- 274.83 kg/m3
That's fully loaded though. Throughout the RPGs the Falcon has always carried about 100 metric tons of cargo. In unloaded configuration, she's 213.49 kg/m3.
Another method for estimation of space warship mass is tanks:
M1A1: 19.7 m3 armored volume, 61,300 kg: 3,111.67 kg/m3.
T-80B: 11.8 m3 armored volume, 42,500 kg: 3,601.69 kg/m3.
T-90A: 11.04 m3 armored volume, 46,500 kg: 4,211.95 kg/m3.
