How it works
After a loss L, the remaining capital is (1 − L) of the starting value. To get back to where it started, it has to grow by L / (1 − L). A 10% loss therefore needs about 11.1%, a 20% loss 25%, a 50% loss 100% and an 80% loss 400%. The curve shows this relationship for losses from 0 to 90%; the red dot marks your input.
The recovery time assumes the same return every year: years = ln(1 / (1 − L)) / ln(1 + r). With the default inputs, a 50% loss and an assumed 15% per year, that is about 4.96 years. The return is your assumption, not a forecast. Real returns vary from year to year, can be negative, and new losses can occur during the recovery. Fees, taxes, deposits and withdrawals are ignored.
The takeaway is about risk control: the deeper the drawdown, the more disproportionate the gain needed to recover. That is why limits on the risk per trade and on the maximum drawdown of the whole account matter so much in systematic trading.