I've been thinking about this for awhile, grades are a rough estimate but very arbitrary, so I've been giving personal ratings to things I do outside. Generally, I down grade things but not always.
I've come up with a simple formula that seems to work for me I'd like to share for discussion and to be flamed.
It only works starting at V4 IMO.
You break a boulder problem down into two sections, rate each of those two sections, then add 4 and divide by two.
The two sections can be just one move thats say v5 or it can be two sections that are a comination of moves.
So if you do v4 into v4 it goes like this, 4 + 4 + 4 / 2= v6
v10 into v8, 10 + 8+ 4 / 2= v11
v6 into v8, 8 + 6 + 4/2= v9
Anyways, I was surprised that I found it to be very accurate when I applied it to boulder problems I've already done, almost perfect.
v14 into v14, 14 plus 14 plus 4 /2=v16
Something that pisses me off about the whole grade system (including this im afraid ;p) is that height has no baring on how hard/easy it makes a move when it clearly does.
In an ideal world this would also be broken down into 2 more sub sections that of ''small move'' and ''big move''. Then by getting the AVG height of a climber (lets say 5.9?) work out if a formula to accurately grade something to him. From that you can easily draw other conclusions as to the true grade for people of other heights.
With ought question their are some routes ive been on where my height felt perfect (one comes to mind as a f7a) where as for my old partner who was much taller im sure the crunched up moves made it at least a 7a+ for him. Also the latest route i done was 7c or so, the crux move was a series of slap ups to get to a sweat spot. He could do it in 2 slaps where i had to do it in 3. Given the fact this was max limit climbing that 1 extra slap up felt like it pushed the grade to me. In that 1 move alone it felt like i had to give 20% more than he did.
Edit: i forgot about that ape index thing or what not, but that is simply a case of factoring in the + or - after the math of a neutral person?.
For example a guy of neutral ape and 5''9 would be similar to a guy of 5''8 and +1? perhaps. In terms of a stretchy v4 feeling like a stretchy 4v to both. Where as to a guy of 5'2 neutral it would feel like a dyno v5?.