For every league that I can think of, the current definition of these are the goaltenders in net at the time of the game-winning goal (the N+1th goal, when the losing team scores N goals).
At some levels of leagues, the published statistics do not allow easily to see whether a goaltender won or lost in overtime - recent KHL statistics have this feature. Here, I've included both into the "T" column.
Some leagues separate OTL and SOL - I combine these here. If I have separate shootout statistics, I keep them separately (in another column).
(2*W + T + OTL) / (W + L + T + OTL)
Note that for seasons with "loser points", this will result in the "average" goaltender having a points percentage of greater than 50%.
GAA = (GA)*(60)/(MIN)
The intent of the goals-against average is to put seasons of different length on an even footing, reporting the number of goals the goaltender gives up (on average) in a sixty-minute game.
Pre-1982 NHL shot (and save percentage) information comes from a second-hand Excel workbook done by Roger Brewer, using data from the Hockey Summary Project (a tremendous endeavor by both). It is not considered official National Hockey League dogma.
SVPCT = (SA - GA)/(SA)
S/60 = (SA)*(60)/(Min)
Note that I vary the definition of a "save" here to include any attempt that does not result in a goal (including shots that go wide). If you prefer, think of this as shootout goals prevented.
For instance, suppose that a league-average goaltender had a save percentage of 90%, and faced 100 shots on goal. The truly league average goaltender would allow 10 goals on these 100 shots. Suppose that our goaltender instead allowed 8 goals. Assuming a binomial distribution (I note that this may not be fair), we can calculate how many standard deviations above (or below) average this goaltender's performance was:
ZSCORE = ((Saves) - (Shots * League Average SV%)) / SQRT (Shots * League Average SV% * (1 - League Average SV%))
Or, in this case:
ZSCORE = (92 - 90) / SQRT (100 * 0.9 * 0.1) = 0.67, indicating that the goaltender was above average but not in a statistically significant fashion.
Truly remarkable performances (good and bad) start at about 2 standard deviations away from average, and the larger the number, the more significant.
(In the calculation of league-average save percentage, I remove the goaltender in question from the totals.)
A league-average goaltender would allow (1 - League Average SV%) * (Shots Faced) goals, and so:
GD = ((1 - League Average SV%) * (Shots Faced)) - (Goals Against)
This statistics, Goals Above Replacement, attempts to quantify that value by comparing how many goals a goaltender prevented above a replacement-level goaltender. On this site, "replacement level" represents the best goaltender that a team could find on short notice with small resource expenditure (either the top goaltender on their minor league team, or the top free agent available). I need to analyze this more rigorously at some point, but here, replacement level is defined as 1.5% below league average (so if the league average goaltender is at 90%, then replacement level is defined as 88.5%). And thus:
GAR = ((1 - (League Average SV% - 0.015)) * (Shots Faced)) - (Goals Against)
SNW% = (Goals Scored^2) / ((Goals Scored^2) + (Goals Allowed^2))
Or in this case:
SNW% = ((1 - League Average SV%) * Shots Allowed)^2 / (Goals Against^2 + ((1 - League Average SV%) * Shots Allowed)^2)
Note that, unlike the goaltender's winning percentage, this metric is guaranteed to be such where a league average goaltender scores out with a 50% winning percentage.
For instance, suppose that a goaltender had an (actual) record of 7-3-0, with a support-neutral winning percentage of 60%. They had ten decisions, and so their support-neutral wins would be 6 (and support-neutral losses would be 4).
On some level, this suggests that things not measurable by save percentage (either team offense, or team defense, or biases in save percentage) gave the goaltender an "extra" win.
Lastly, I should note here that, while save percentages are considered a decent statistic for evaluation of a goaltender's individual performance (certainly better than goals-against average or wins and losses), it is by no means a perfect statistic. I will write more to this at a later date, but for now, please keep that in mind.