Here's a nice list: https://en.wikipedia.org/wiki/List_of_physical_constants https://en.wikipedia.org/wiki/List_of_physical_constants G (the gravitational cons

Here's a nice list: https://en.wikipedia.org/wiki/List_of_physical_constants https://en.wikipedia.org/wiki/List_of_physical_constants G (the gravitational constant) is an interesting one: the value is only known to about 5 significant figures, but GM (the gravitational constant multiplied by the mass of the Earth) is known a lot more accurately, unsurprisingly, considering how well GPS works. Some of those constants seem to be known to about 12 significant figures.