Estimate it directly: required gain is 1 / (1 - drawdown) - 1, and recovery time is roughly that divided by the strategy's periodic return. A 25% drawdown needs 33.3%; in a strategy compounding 1.2% a month, that is about 24 months of uninterrupted performance.
Two adjustments make the estimate honest. First, if a drawdown-throttle cuts size during the decline, recovery runs slower than the raw figure - possibly half as fast. Second, the strategy must still work; the environment that produced the drawdown does not politely end at the trough.
The output of this calculation is usually a decision about limits. Most traders, when they see that a 35% drawdown implies a three-year recovery, tighten their loss limits rather than accept the number. See drawdown-recovery-maths.
Related: drawdown-recovery-maths, drawdown-duration, drawdown-throttle, monthly-loss-limit