Click on the Playoffs subtab of the League tab during your final regular season week for a detailed breakdown of possible playoff scenarios.
You'll see your odds of making the playoffs, winning the division, and earning a 1st round bye.
You'll also see what needs to happen for those outcomes by mousing-over the % value.
How is this calculated?
By simulating every conceivable win-loss outcome for your league's final regular season week.
Please note that this analysis doesn't account for changes in total points tiebreakers (so if you hold a slim lead in Total Points Scored and your league relies on that tiebreaker, this analysis assumes you'll continue to hold that lead after next week).
So it might say that you've been eliminated when you still have a shot at overtaking another team in total points scored.
How is this different from the clinching symbols on the standings page?
The clinch symbols on the standings page use a very simple analysis relying on current win-loss and number of games remaining. They do not factor future schedules into account. The playoffs page will have more accurate results.
Let's try this one for an example... fleaflicker.com. Hover over team 7's 25.