Picard (in TNG : The Offspring) offers his own assessment of Lal's physical strength. Since she was based on Data's own physiology, it's likely her strength is similar to his.
Obviously he's using hyperbole but there's no reason to assume his assessment is wildly inaccurate:
PICARD : (frowns)
If he must, fine. But I don't understand how he can call a five foot android, with heuristic learning systems and the strength of a ten men
We see him carrying a 2-300 pound anvil with one hand in "TNG: Times Arrow". Someone with the strength of 10 men could easily accomplish this feat.
Data casually reaches down with one hand -- AND PICKS UP THE ANVIL as
though it weighed an ounce. He starts toward the center of the room --
there's a noise of astonishment from the Bellboy.
and of course the most obvious feat of "meta-human" (mega) strength from TNG : Measure of a Man
Riker : Your honor, I offer into evidence
prosecution's exhibit A. A bar
of plasteel with a tensile
strength of forty kilo-bars.
Data easily bends the bar.