Cabin pressure is generally held around 6-8,000 ft equivalent, which would give a pressure of around 81% of sea-level pressure.
I can't think of anything except Concorde cruising above 50,000 ft, which would give a pressure of around 12% of sea-level pressure.
81-12 = 69, say 70% of sea-level pressure as a worst case difference across the cabin.
Sea level pressure is 101,325 N/mē, so 70% of that is roughly 71,000 N/mē. That's a fair estimate of the worst pressure difference seen across cabin walls, doors and windows.
To put that in more commonly used units, that would be equivalent to 7 grammes per square millimetre, or 10 pounds per square inch. Your car tyres are probably inflated to about 3 times that difference across the tyre walls.
Doors don't burst open in flight, they can't. The door is shaped such that the pressure difference pushes it further into the hole - if you wanted to open a door you'd have to depressurise the cabin first. If anything fails, it's more likely to be the central cabin around the hoop-ribs, and this has happened once or twice but is extremely rare and usually only following a fatigue failure - an overpressure alone wouldn't do it. Modern inspection regimes should ensure that any fatigue damage is identified and checked long before it gets close to that stage - we've all been understandably a little paranoid about the subject since the Comet !
G