Usually I post the Manhattan Neighborhood Map for touring Providers. "Is Tribeca close to Morningside Heights?" (No! It isn't!)  
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Then, most local yokels know that, in Manhattan, there are 20 city blocks per mile. That's the E-W numbered streets, not the N-S Aves. Walking on a N-S Ave. (e.g., 6th Ave.), 34th St to 54th St. is one mile.  Obviously, that rule breaks down where the streets get broken and curvy; it's a rough guide for the central Manhattan grid.  
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Then, not everyone will know what DONY is. If it is one of your DESIRES to know more OF NEW YORK, you sometimes need to get someone's time and attention more clearly. Some people reading this might know the full name but not an abbreviation that isn't used as much as, say, the old JoNY.  
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Lastly, check out google maps. Enter a destination and a starting point (Penn Station) to get directions. Options include Driving, Public Transit, WALKING, Ubering, and Cycling. You get the routes and the times to travel those routes.  Let's see ... From Penn Station to Carnegie Hall is a 1.3 mile, 25 minute walk. Or, you could just practice.