Risk per trade with a trailing drawdown: the math

On a trailing drawdown account, measure your risk per trade against your buffer, the distance between your current balance and the floor that fails the account. On a 50,000 account with a 2,000 trailing drawdown, 1% of the balance is 500 dollars, a quarter of that buffer, so 4 full losses in a row take you to the floor.

The three numbers behind every size

A trailing drawdown is a maximum-loss rule whose floor sits a fixed distance below the highest balance or equity the account has reached. Each new high lifts the floor, and a pullback leaves it where it is.

The floor is the level at which the program closes the account. The buffer is balance minus floor: the money you can still lose before that happens.

Risk per trade is what a position loses if its initial stop is hit: position size times stop distance, plus costs.

Risk as a share of the buffer

A fresh 50,000 account with a 2,000 trailing drawdown has its floor at 48,000 and a buffer of 2,000. Divide the buffer by your dollar risk and you get the number of full losses in a row that reach the floor.

The count assumes each loser costs exactly the planned amount. The table prices each row; which row fits your strategy is your decision.

The same 1%, measured two ways

Position sizing is choosing how many units to trade so that hitting the stop costs a planned amount: position size = risk per trade ÷ stop distance per unit. Textbook sizing sets that amount as a percentage of account capital.

On this account, 48,000 of the 50,000 sits below the floor. Here is "I risk 1%" read both ways:

Same sentence, 25 times the dollar risk per trade.

Room for 4 losses is thin. At a 50% win rate, the chance of at least one run of 4 or more losses in 100 independent trades is 97.3%. Before any lock, the buffer can never exceed 2,000, so 4 losses at 500 reach the floor wherever the run starts.

Seen from the other side, 200 dollars is 0.4% of the balance and 10% of the buffer, which allows 10 full losses.

Why a new high leaves the buffer where it was

A static drawdown keeps the floor at a fixed distance below the starting balance. Say a good week closes at 51,000, a new high:

The static account turned the gain into buffer. The trailing floor climbed 1,000 with the balance, so the buffer is still 2,000. The full comparison is in static vs trailing drawdown.

Sizing from the balance makes it worse: 1% of 51,000 is 510, and 4 such losses (2,040) overshoot the buffer.

Intraday trailing adds a trap. When the program tracks equity through the session (balance plus open profit and loss), a peak you never banked lifts the floor too.

On the fresh account, a trade that runs 1,200 into the green and closes at breakeven leaves the balance at 50,000 and the floor at 49,200. At 200 per trade, that's 4 full losses left instead of 10, after a flat day. More on that case in does trailing drawdown include unrealized profit.

What changes when the floor locks

A lock, also called a freeze, is a clause that stops the floor from trailing once it reaches a set level. Many programs set that level at the starting balance; others trail for the life of the account. Here a lock at 50,000 engages when the peak reaches 52,000, after 2,000 of profit.

Before the lock, 2,000 is the most buffer this account can hold. After it, each dollar of profit adds a dollar of buffer: 200 fits 15 times at 53,000 and 20 times at 54,000.

Your agreement says whether yours locks, at what level, and whether an open-profit peak can trigger it.

Pick the streak, then divide

An R-multiple is a trade's result divided by its initial risk, called 1R. In R the buffer becomes a count: at 200 per trade, 2,000 is 10R.

That turns the question around: decide how many full losses in a row the account has to survive, then divide the buffer by that number. The number is your call. Your log is the evidence for it, and the longest run in a sample tends to grow as the sample grows.

Two habits keep the count honest. Recalculate from the current buffer at the start of each session: after 3 losses at 200 it's 1,400, and 200 fits 7 times. And count losses past the stop at their real size: a moved stop that turns a planned -200 into -340 is -1.7R and uses 1.7 of your 10.

Our trailing drawdown check returns your floor and buffer from your highest balance, current balance and trailing amount. GlanWick shows your longest losing streak and your R-multiple distribution with expectancy in R on every plan, and the drawdown chart from Starter. The journal itself is free.

Short version

Measure risk per trade against the buffer, balance minus floor, which tops out at the trailing distance until the floor locks. On a 50,000 account with a 2,000 trailing drawdown, 1% of the balance means 4 losses to the floor and 1% of the buffer means 100. Pick the streak you need to survive, divide, and recalculate each session.