How does the mass of a planet or object effect its gravitational pull?

The gravitational "range" will be the same whether or not there is mass in the way if gravity will have an effect on an object for 100 miles but there's 50 miles of land in the way, it will still affect the 100 mile radius. so it really does if the range is 4000 miles and the planet is 2000 miles thick then the pull will be weaker than that of a planet 1000 miles thick bc you are closer to the source of gravity