Calgary has a 28.8% chance of making the playoffs according to
SportsClubStats - though it drops to 16.2% if you
weigh goal differential, which typically gives better results.. I don't think people realize 3 points out of a playoff spot' is actually significant when there's actually 4 teams you have to hurdle to get in.
To have a better than 2/3rds chance, the Flames need a run of roughly
21-12-4 - about 46 points in their last 37 games. That would take them to 93 points on the season, which is on the low side; last year the Dallas Stars sat the post-season out with 95 points..
It's doable, and a 21-12-4 record doesn't look all that scary, but to put it in perspective, that's a 0.621 points %... 8 teams in the NHL have a percentage better than that right now, so Calgary has to basically be in the same league as what the Bruins, Rangers, Flyers, Sharks, Canucks, Blues, Blackhawks, and Red Wings have done up until now. Basically, they have to be a top-8 team in the league.
Behind Calgary is Edmonton/Anaheim/Columbus, they won't catch up and are basically assured of finishing in various orders of 13-14-15.. Ahead of Calgary and likely fighting with them is Phoenix, Colorado, Dallas, Minnesota, Los Angeles. Two of those teams get in (three if Nashville drops out, but Nashville is quietly 9th in the NHL again).
Los Angeles, Phoenix, and Dallas all play a lot of games against each other, which means there's a lot of nights where its guaranteed one of those teams is taking home 2 points and possibly a 3rd to the other. Calgary has to win every time there's a game between those Pacific foes
just to keep pace. Gaining 3 points on 4 different teams when you've played the most games of anyone won't be as easy as "3 points" sounds like. Like the numbers said, somewhere between 16%-29% likely.