Let’s say Magnus Carlsen went up against some amateur novice, and Carlsen agrees to go with a materiel disadvantage. How much would it have to be to be a fair 50/50 battle?
Would Carlsen have to go without his queen, both rooks, and one horse or bishop?
I say, old boy - we call it a knight! 
Seriously, we know how strong Carlsen is.
You need to define precisely what you mean by ‘amateur novice’.
When I was a professional chess teacher (rated 2200+), I taught a wide range of abilities.
For complete beginners I started with the moves of the pieces.
After they had mastered those, I would show them very simple endings.
Occasionally a pupil would challenge me to a full game (even though they weren’t ready for it.)
I would humour them by taking off my Queen and both Rooks - and also playing blindfold.
It was pretty easy to win - usually by taking their pieces, but occasionally with a checkmate.
Or another way to look at the question: What level of player would be able to beat him, at each level of handicap? @glee , if you were to play against Carlsen, what handicap would you consider fair?
I would add - at tournament-length time controls.
Relevant recent-ish thread here:
Interestingly I have a real-life answer! 
On April 21-2, 2001 Garry Kasparov played Terence Chapman a series of four games - two per day, alternating colors - at odds. (Kasparov also had a time disadvantage.)
Chapman was a very strong junior player, who became a successful businessman (then retired and did even better at chess.)
In 2001 I think he had about a 2150 rating
odds White Black
Game 1 Kasparov removes his a and h pawn Chapman - 0 Kasparov - 1
Game 2 Kasparov removes his a and d pawn Kasparov - ½ Chapman - ½
Game 3 Kasparov removes his a and b pawn Chapman -1 Kasparov - 0
Game 4 Kasparov removes his a and e pawn Kasparov - 1 Chapman - 0
Kasparov won overall 2½ - 1½
The games are here (you’ll need to scroll down a lot…)
The Romance of Chess - Chess.com
I think it’s reasonable to compare Kasparov - Chapman with Carlsen - glee.
So I would ask Carlsen for a piece start.
Seriously, note that the stronger player loses all his opening knowledge (a real help to the weaker player.)
Less seriously - Chapman made a £100,000 donation to Kasparov’s chess academy.
If the Straight Dope members would like to raise a similar amount, I’ll contact Magnus! 
My father was a very good chess player, but nowhere near a Magnus Carlsen. I was literally the kind of player who would lose in the second round of the high school chess club tournament. My father could spot me the Queen and play black and still beat me easily.
I’ve mentioned this anecdote before, but it does illustrate just how much world-class players know about the game.
When I reached my peak rating of 2390, I was playing in a tournament section for FIDE and International Masters. The Grandmaster section included John Nunn (top English player and decent chap.)
We were discussing chess one evening when John remarked “Players below 2400 don’t really understand chess!” 
He wasn’t being nasty, but after he explained (and gave me some analysis) I saw what he meant.
Chess is a really deep game.
A novice means someone brand new to the game, so the material advantage would have to be absurd for any novice to have a chance because novices are known for making ridiculous blunders.
To put it in perspective, my brother started teaching me chess when I was six. I ended up on my chess team in high school and, at the top of my game, might have been an 1800 or so player. That’s pretty good for an amateur, but well below professional standards. He would at least have to play without his queen for me to have a chance, and I say just a chance. I would have to play conservatively with the goal of reducing material whenever possible to take the venom out of his creative attacking abilities. Even so, his fabulous opening repertoire might do me in.
Have you ever read the great short story “The Three Sailors’ Gambit” by Lord Dunsany? Some people can play with a pretty big handicap!
Thanks, hogarth. An interesting little story - never read that before! I’ve passed it along to my father and some other chess-loving friends.
This thread may also interest you: HAL 9000 Playing Chess in 2001
I’ve often wondered about other ways to handicap chess:
The grandmaster is allowed one move per turn, as in normal chess. The novice is allowed two (or more?) moves per turn.
The grandmaster’s pieces move and capture as per normal chess rules. The novice’s eight back-line pieces all move and capture like queens.
Same as (2) above, except the novice’s pawns also move/capture like queens.
Same as (2) above, except the novice’s back-line pieces all move/capture like queens or knights.
Same as (3) above, except all 16 of the novice’s pieces move/capture like queens or knights.
Could a grandmaster overcome some or all those handicaps against a novice?
My guess is a novice player would beat a grandmaster most of the time under all of those rulesets. Very difficult to checkmate the novice under set 1, if they can move twice to escape!
Yeah, any of those handicaps could be pared back some.
You could have a rule that instead of the novice having two moves per turn, they could have two moves every other turn, or every third turn. Or you could have the novice play with a smaller number of queens than eight – maybe the king stays normal and all of the rooks, knights, and bishops become queens. Or just the rooks and bishops. Or whatever.
ISTM that one could argue that in some sense chess isn’t really well suited to handicapping for just this reason – it fundamentally changes the nature of the game, which technically is no longer really chess, but some other game that resembles it. Unlike golf, for instance, where the strategy is always the same, and a player’s handicap is just a numerical representation of the degree to which he can’t hit the ball worth a shit.
Also very difficult for the grandmaster to escape checkmate if they’re being checked on move one of a two-move combo. There’s probably some pretty easy force mates for the two-move side under these rules. (Assuming you count king capture as a mate.)
The other ones all seem too much of an advantage. In the other thread, the removal of a queen was likened to about a 2000 elo disadvantage, although that probably (almost certainly, I would think) doesn’t scale down to the 300-500 truly novice level.
There was a video I watched the other day of an ~ 2000 FIDE player (Nelson Lopez) play Stockfish at its level 8 setting (which he said was 3000 elo), progressively giving himself more and more odds, and he only finally beat it at queen odds, so in that case, it was about a 1000+ elo advantage.
I wonder how much – in an otherwise normal game – just having an extra queen or two helps a novice? Say instead of bishops, the novice has three queens (their normal queen and two more in the bishop slots).
I’d think the grandmaster would be essentially unphased, but I’m admittedly speculating.
Yeah, the thing is the novice will not know tactics that well, so it’ll probably be somewhat easy to pick off a queen or two with a fork or something of that nature. It does get wild when dealing with those ultra low ELOs.
Yeah, I don’t think rule changes would be good for this hypothetical. It messes everything up and it’s not real chess anymore.
Better yet to keep things within existing rules, but instead just add pieces for the novice and subtract them from the grandmaster’s. So maybe the novice gets 4 queens and the grandmaster has none.
I’m picturing an average layman, such as myself who has never played a competitive game of chess in my life, and in my whole life has played maybe only 50 games against family, friends and computer software.