Hulk's strength varies with his anger. The more infuriated he gets, the stronger he gets also.
During the Secret Wars, Hulk held a mountain on his back:
That's 150,000,000,000,000 kilograms. Should be more than most other characters of his size could bear. But this is just a bad hair day anger for him. During the Planet Hulk series, the main antagonist used a device that caused the planet Sakaar to break apart. Massive rifts appear in the surface of the planet as it starts to break. So Hulk jumped onto bedrock and magma and held the two halves of the planet together.
Even if we suppose that Sakaar has the same mass as Earth, I don't know how to calculate the forces involved in this particular scenario (and this is the kind of exercise that I am used to participate in, in the worldbuilding stack). But just as a mental exercise, if he can do that, he could probably do the opposite and pull two halves of an Earth-sized planet apart, if sufficiently angered. That would mean he could hold approximately 3x1023 kilograms on his back.
Let me rewrite that without scientific notation:
That would mean he could hold approximately 300,000,000,000,000,000,000,000 kilograms on his back. You could also say three hundred sixtillion kilograms (or three hundred quintillion tons), or three hundred zettakilograms.