I know this is obviously very subjective as some people are better in shorter distances, and some people are better in the long races, but in everybody's opinion, a 16:00 5k would be an equivalent performance to what time for a marathon?
I've tried those running calculators on different websites, but I think those things are very poorly constructed, so this is why I am asking for all of your opinions?
Mid 2:30s
A marathon specifically trained runner that can run 16flat should be able to go low 2:30's on a flat course.
A 5k specialist who is just doing some extra long runs and what not, should be about 2:40
2:34 - 2:35
THIS! I know 4 runners who bounce around mid-16's and just started adding easy runs of 20+ miles. None of that formalized 10 easy/10 marathon pace = 20 miles Hanson's/Brooks stuff. They all hit 2:40-2:45's in their marathon debuts. One guy who had 15:XX in HS XC (16:03 on the roads as a 9-5 working man) hit 2:35 when legitimately training for it.
Running in the Rain wrote:
A marathon specifically trained runner that can run 16flat should be able to go low 2:30's on a flat course.
A 5k specialist who is just doing some extra long runs and what not, should be about 2:40
If you ran a marathon at the same level of excellence as a 16 flat 5km you would be in the 2:35 range. BUT because you can run 16 flat does not mean you can run 2:35. As you point out some folks are better at shorter races and some at longer.
Both 9.58 and 2:03:38 score in the 1115-1120 range on the Portuguese scoring tables/Purdy system but that does not mean Patrick Makau will go stride for stride with Bolt in the 100 nor that Bolt will be able to tick off 4:45 miles for 26 plus miles.
I am more comfortable thinking a 2;35 marathoner can run near 16 minutes for the 5,000 than I am a 10 flat hundred guy can post a 2:11;30 marathon after all we KNOW an 2;35 marathoner can cover 5KM in 18:30 at minimum and do it 8 times in a row. We have NO idea at all how fast a 5km a 10 flat guy can run.
contrary to popular belief, bouncing around in the mid 16s is not 16 flat
I run around 16 flat, yet am more an 400-800 meter runner. I had to train hard to run that fast in the 5k. I can't run a fast clipped long run to save my life. My long tempo runs are always too slow. Although, I haven't run a marathon, I don't think there is anyway in hell I could ever break 2:40.