Don't know if anyone did it before but I tried to remember what was the state of each army in Westeros, mixing books and show there
Stark : Well we heard from Jon and Davos that they have <10k
Lannister : At the beginning Tywin said he gave Jaime half of his army to go fight the Stark, the whole army was 60k. From there Jaime probably lost a good chunk of it, I don't know if part of the Lannister army was involved in Blackwater, however they probably lost a bit during the Riverrun siege, a few thousands were probably lost when the Unsullied took Casterly Rock also.
Overall ~25-30k might give a rough idea of what they had left before this episode
Tyrrel : I think at the beginning the number of 100 000 soldiers was mentionned, it also included a few Baratheon (some going for Stannis afterwards and some... going home I guess) they might have lost a few at Blackwater but not much, Tarly did some battles he won on the book but not on the show, overall the number shouldn't have changed that much so <80k (Tarly included)
Considering Tarly is a vassal to House Tyrell, anything above 20k for his own army would be ludicrous imo
Martell : Can't remember the exact number but I think it was around 40-60k in the book, they never fought a single battle, only Oberyn was killed and Sand Snakes & cie only had a small Martell escort with them as far as we know
So <50k
Arryn : Outside the battle of bastards where they just crushed the Bolton they didn't fight another battle, from the 7 houses I think it was one of the smaller army from the start like 20-30k, that number probably didn't change much
Baratheon : Nothing left in the show I guess lol (Stormsland is probably empty like Dragonston was!), in the book Stannis still have something like 5-15k iirc
Greyjoy: Big unknown as I can't remember any number being mentioned at any point, though asides from Theon and Asha/Yara who lost a few hundreds men in the north they are pretty much untouched at this point
In the show we have the 1.000 ships number (lol), stupid maths tell me there should be between 15-30 people by ship so it makes <25k
Targaryen: 100k Dothraki I think (or even more?) and the Unsullied which were around 10k at the beginning probably less now
So <110k I think
Daenerys was so powerful at the end of S6 that she had to be nerfed somehow, but it clearly wasn't done in a subtle way.