what percent Elf is Aragorn, for that matter? This gets complicated very quickly. Dior is ¼ Elf, ¼ Maia, ½ Man, so his children are 5/8 Elf, 1/8 Maia, and ¼ Man. Eärendil is ½ Elf and ½ Man, which makes Elrond and Elros 9/16 Elf, 1/16 Maia, and 3/8 Man. Elros’ children would be 9/32 Elf, 1/32 Maia, and 22/32 Man. If there was no intermarriage with anyone descended from Elves, then after five more generations you’d get people who were 9/1024 Elf, 1/1024 Maia, and mostly Men.
But by the time of the marriage of Erendis to Aldarion, it was already unconventional for the King not to marry within the royal family, and after that marriage failed it became even more unconventional. If we assume the Lords of Andunië kept the same policy (which seems likely, given their persistent extended lifespans) then, by the time of the sixth generation, all royal marriages were between people in the same genetic pool (that is to say, between people who are all around 9/1024ths Elven, 1/1024th Maia, and 1014/1024th Men) and the percentage of Elven blood wouldn’t decrease from there.
It’s still not that simple - if any descent from the King sufficed, then you might still have people with only a dash of Elven blood - people who’ve been out of the royal intermarriage pool for a dozen generations - still qualifying. That means the percentage of people with royal blood would keep decreasing! - but we also assumed no intermarriages within the royal line before Aldarion, and we know that those happened. I suspect that the ruling class all the way through to Arnor and Gondor was around 1% Elven by blood. The biggest source of the differences between Númenoreans and mainland Men would have been because of the alterations of the Valar toward their favored people, not because of the Elven descent.