Drawdown is the difference between peak values and lowest values(troughs)
For example if a portfolio starts being worth $100,000, increases in value to $150,000, decreases to $90,000, increases to $120,000, then decreases to $80,000, then increases to $200,000, the max drawdown is ($150,000-$80,000)/$150,000 = 46.67%
Maximum drawdown formula
Max Drawdown = (Peak value before largest drop-Lowest value before new high established)/(Peak value before largest drop)