how far is penn station from the marriot marquis in times square. is it walkable or do you need to take a cab?

Certainly is walkable unless you are hauling a lot of luggage. About 10 blocks up 8th Avenue ( 1/2 mile ).

It is betweem 1/2 and 3/4 of a mile, certainly walkable. Penn Station is at 33rd Street and the Marriott Marquis is at 45th Street, which is 12 blocks. In New York, 20 north/south blocks equals one mile

If you decide to walk exit Penn Station to 7th Avenue. You will be at 32nd Street and, as was pointed out, the hotel is at 45th St. If you decide on a cab exit Penn Station onto 8th Avenue since 8th is a one way northbound avenue

I've done it with luggage in tow. Just exit Penn and walk up 7th Avenue. It is a great walk.

walk it, unless you have alot of luggage. it's right up 7th. cabs are uneccassarily expensive.

The distance from Penn Station to the Marriott is the same distance as Penn Station to my office....and my commuting coworkers ALL walk it...even the retirement-age ones.

NYG, just keep in mind that though it is a pretty painless straight walk, if you are not used to walking in crowds, and you happen to be making this walk in the afternoon (maybe 4pm to 6:30) it can be a little rough if you have any bags/luggage at all. You might find yourself trying to hold onto a purse or tote bag with one hand while trying to maneuver a small wheeled bag with the other hand Of course, those are exactly the times that a cab would be near impossible, too, but you could take a short bus ride up 8th avenue (number 10 or 20 bus, I always forget the number, but there's only one bus line there) that will take you an avenue away from the hotel.
If you're totally without baggage, and/or making the trip at an odd hour, there will be no problems whatsoever