What ratings are equivalent to these checkmates?

I would guess 

queen 700

rook 1000

2 bishops 1400

knight+bishop 2500

knight + bishop 2500? lol I know a 1500 who can do it

One of the worst players I knew could do a B+N mate from any position on the board. It's not rating specific.

I think that each player is different and some are naturally better at endgames than others. On the flip side, lesser rated players are still capable of learning checkmates and patterns associated with ratings above their current level. It isn't accurate thinking to associate ratings to what checkmates they are confident in playing; plus, knowing a theoretical endgame is one thing and mastering it under time pressure is another. 

I won't assign accurate "ratings" to checkmates because even the simple ones vary. For instance, Queen + King vs King might be failed by even 1000-ish players, but another 500-ish player might have practiced it.

What I will say though is that Queen is the easiest, Rook is close behind, but 2 Bishop checkmate and Bishop + Knight take slightly more insight because piece coordination is more important.

By 1500 rating I'd expect them to know all of these checkmates except for maybe B + N. Probably by 1600, almost everyone knows B + N though. There have been some embarrassing cases where titled players fail B + N mates, but it is usually just because they learned it as a child and haven't used it since (so they forget the exact technique), or they know it: but not well enough to solve under time pressure.

Personally, I can probably checkmate with only B + N within 3 minutes from any position (assuming that any immediate capture of a piece isn't possible at the moment) and I am nowhere near 2500 rating.

Wikipedia has an extensive write up about the N/R mate combo. While it does not give ratings, it does note, "Delivering checkmate is difficult if the technique has not been studied and practiced. Even grandmasters, including GM Vladimir Epishin and Women's World Champion GM Anna Ushenina, have obtained the endgame but failed to win it."

As this ending is so rare I have not studied it and likely would be unable to do it.

So if GMs fail to succeed, I would guess 2200+? But I think knowledge of the method and opponent strength are more important.

I would say rating is totally irrelevant.

Anyone of average intelligence could solve the first three over the board immediately after learning the rules.

Anything harder depends on whether, and how much, you've looked at it, not what your rating is.

(That is if you're talking about exact solutions. When the position can't be accurately evaluated, e.g. the starting position, then rating applies - but even there it depends a lot on how much you've looked at it.)

I think you mean B + N. Yeah, this is definitely the toughest of the ones mentioned though. A big key to solving it is knowing some B + N mating motifs and to slowly corral the enemy King using coordination among your pieces (specifically trying to set up the Knight to control squares of the color that the Bishop can't cover).

There's no reason to suppose @little_guinea_pig means KBNK.  As I said earlier, most people of average intelligence would manage KBBK over the board, even if they had only just learned the moves. They have only to work out how to avoid stalemating. As little_guinea_pig says - it's not that hard... (unless your bishops are on the same coloured squares of course).

Edit: @KeSetoKaiba apologies. I hadn't spotted @little_guinea_pig's misprint. I thought you were talking about his second sentence.

fun fact rook + 3 bishops on same color square beats rook +bishp from opposite color I analysed it

Curious omission of pawn and two pawns from OP's list.

A lot of beginners, even smart beginners, don't yet have the chess intuition to identify key concepts to K+Q and K+R mates, namely opposition, and the idea that you don't have to give checks to win. At the same time. K + Q is easy to learn and K + R isn't that much harder, and since they come up a lot, anyone who plans to get better at chess should learn them, regardless of rating.

queen-400 rook- 800 or 900 2 bishops - 1200 N+B- 1700

You mean Bishop AND Knight?

King + Bishop vs King as well as King + Knight vs King are both draws. Checkmate isn't possible due to insufficient material to checkmate with.

Conversely, King + Bishop + Knight vs King is possible, but tough to do and I'd estimate roughly 1800+ level for those who haven't deeply studied this theoretical endgame. If you need help with this checkmate, here is how to do it:

i am 1100, i can do bishop and knight, i don't think rating plays that much of a part in queen/rook+king vs king endgames as the patterns are quite easy to learn from opponents when they achieve that endgame, meaning that i believe that endgame just comes from playing the game, bishop and knight/bishop are things i wouldn't say is something you learn with rating as they are patterns, any functionable human being can learn a pattern.

That was my rating estimate IF they DIDN'T study this endgame; if you study this endgame well (regardless of rating), then you probably know it well.

Most 1100s don't know the advanced Bishop+Knight checkmate. Even Grandmasters sometimes fail this checkmate in games (time pressure, forget the technique learned years ago etc.).

ratings dont directly correlate with endgame knowledge, as anyone can memorize a pattern

how bout K+N+N vs K+P

This endgame is a draw with best play UNLESS the pawn is not advanced far enough and the side with the Knights has the precise technique for converting this by blockading the pawn and releasing the blockade at the critical moment. This endgame is a win with best play in that situation. Dvoretsky's Endgame manual details the specifics of this ending, but this book is renowned for being extremely advanced...even for titled players.

This in mind might make you smile at this clip

two bishops is possible for someone of average intelligence easily w/o knowing the technique beforehand

guess i dont have average intelligence then!

yeah idk what the people who said this were thinking

the technique, what do you do even??

you need the king.... but then it blocks the bishops...

i say good luck to beginners who dont know queen mate to figure this out over the board

wait first off they need to be up two bishops without any pawns

that is a 1/10000 possibility at the level

and to #17, i am the 1100 who doesnt know two bishops mate

as if it will ever occur lol

The ratings are irrelevant if you know them you can do them