I created a new tool to estimate the time at which a trailing defense (or soon-to-be-trailing defense) can get the ball back if they force a stop. The results are based on the time at the first down snap of a series and the number of timeouts remaining for the defense. You can adjust the expected duration of each play and the time consumed between the previous whistle and the next snap when the game clock is not stopped. The defaults are 6 and 39 seconds respectively. The calculator assumes there will be no stoppages due to reasons other than timeouts and the two-minute warning, such as incomplete passes, runs out of bounds, or penalties.
One additional feature is that you can check a box called "Save Timeout." This will indicate that the team on defense would prefer to allow the clock to wind down to the two minute warning rather than stop the clock with a timeout. For example, if the defense has one timeout left and the second down play ended at 2:10, the defense can elect to save the timeout for its offense in exchange for running down the 10 seconds to 2:00. This is, in effect, a trade-off between the 10 seconds of game clock and having a timeout available for an offensive drive.
It's very difficult to quantify the value of the timeout on offense. It's intuitively very valuable because an offense can use the middle of the field, which otherwise allows the defense to guard the sidelines.
Try this: Enter 2:24 remaining with 3 timeouts. Leave the 6 sec and 39 sec defaults for play and inter-play durations. Click calculate with the Save Timeout option unchecked and checked (with the 12-second default cutoff value). With 'Save Timeout' checked, you get the ball back with 1:54 and retain a timeout for your offense. Without the option checked, you get the ball back with 2:00 on the clock and no timeouts, with the 2-minute warning essentially going to waste.
This option usually only makes a difference when the defense begins the series with all three timeouts remaining. It also may be smart depending on when a team can expect the change of possession to occur. The defense does not want change of possession to occur on a play that spans the two minute warning because that combines two potential clock stoppages into a single stoppage.
The workings of the NFL game clock is far more complex than it might seem. That's why I forced myself to build the calculator and think through all the considerations. The algorithm behind the calculator is basically a by-product of the one I used to create the chart below, which underpinned my analysis of when a defense should prefer to intentionally allow a TD.
There are two differences between the chart and the calculator. First, there is the 'Save Timeout' option in the calculator. And second, the calculator results walk through each play of the series and spells out the details of clock times, the timeouts, and the two minute warning for each situation.
You can game the calculator a little to account for some contingencies. If the ball goes out of bounds, the offense throws an incomplete pass or there is a penalty, there would be an additional stoppage, sparing a timeout for the defense. To estimate this possibility, just add a notional timeout to the actual number remaining. And if the defense already started with a full three timeouts, you can add one to the resulting number remaining at the end of the series.
As with everything around here, this is in indefinite beta status. Let me know if anything is buggy.