By EdgeSizer · Updated May 2025
Trailing drawdown is the single most misunderstood rule in prop firm trading. Traders read it, think they understand it, and then blow their account in week one wondering what happened. It doesn't work the way most people assume — and that gap in understanding is exactly why the failure rate on funded evaluations is so high.
This guide breaks down trailing drawdown with real numbers so there's no ambiguity. How it rises with your equity. How it never moves back down. And the counterintuitive trap that catches traders who start their combine with a big winning streak.
Trailing drawdown is a floor that follows your account equity upward. Think of it as a line attached to the highest point your account has ever reached, hanging a fixed distance below it. As your equity rises, the floor rises with it. But if your equity drops back down, the floor stays exactly where it was — it never moves down.
Let's trace through a concrete example starting with an Apex $50K evaluation, which has a $2,500 trailing drawdown.
| Day | Account Equity | Equity High | Drawdown Floor | Buffer Remaining |
|---|---|---|---|---|
| Start | $50,000 | $50,000 | $47,500 | $2,500 |
| Day 1 (+$800) | $50,800 | $50,800 | $48,300 | $2,500 |
| Day 2 (+$1,200) | $52,000 | $52,000 | $49,500 | $2,500 |
| Day 3 (-$600) | $51,400 | $52,000 | $49,500 | $1,900 |
| Day 4 (-$1,500) | $49,900 | $52,000 | $49,500 | $400 |
On Day 4, you only have $400 of buffer left — not $2,500. This is what shocks traders. Two good days raised the floor, and then two losing days squeezed the buffer to almost nothing. One bad trade wipes the account.
Here's the counterintuitive part that catches even experienced traders: winning early makes your situation more dangerous, not safer.
If you run up $3,000 in profit in your first week on a $50K account with $2,500 trailing drawdown, your drawdown floor is now at $50,500 — above your starting balance. Your account is at $53,000, but if you give back that $3,000, you blow the evaluation. You don't get to "use" the profit you built. The trailing floor already followed it up.
Traders who go on a hot streak early often press their size, give some back, and suddenly realize they've already used up the cushion they thought they had. The solution isn't to avoid winning — it's to reduce size as the trailing floor rises and your buffer tightens relative to your trading style.
Not all prop firms trail the drawdown the same way. There are two main approaches:
The drawdown floor updates in real time based on your current account equity, including open positions. If you're up $500 on an open trade, the floor rises immediately — even before you close the trade. This is the stricter version. You can be sitting on unrealized gains, have the floor rise, then watch the trade retrace and now you're closer to the floor than you expected.
Some structures only update the trailing high at end of day, based on your closed P&L. Open positions don't affect the floor until you close them. This gives traders more intraday flexibility, but the same overall logic applies — once equity peaks, the floor locks in.
These two firms handle the downside protection differently, and the distinction matters for how you approach trading them.
| Feature | Apex Trailing DD | Topstep Max Loss Limit |
|---|---|---|
| Structure | Trailing from equity high | Fixed floor (does not trail up) |
| $50K account | $2,500 trailing | $2,000 below starting balance |
| Does it follow profits? | Yes — rises with equity | No — fixed at $48,000 |
| Daily loss limit | None on most accounts | Yes — separate daily limit |
| Risk if you go on hot streak | Higher — floor rises | Lower — floor stays fixed |
Topstep's Max Loss Limit is significantly more forgiving from a trailing perspective. If you start a $50K Topstep combine and your account goes to $55,000, your loss floor is still $48,000 — it doesn't follow you up. You now have $7,000 of buffer, not $2,000. This is a meaningful structural difference that makes Topstep's rules more prop-friendly for traders who go on early winning streaks.
Apex's trailing drawdown also eventually "locks in" once your profit target is reached — on some accounts the trailing stops trailing once you've hit the profit goal. Verify the current rules with Apex directly, as they update their structures periodically.
1. Size conservatively in week one. This cannot be overstated. Your first few trading days set the equity high. If you blow up in week one, you never had a chance to prove your edge. Use 50-75% of your normal size until you've established a positive cushion.
2. Track your buffer, not just your P&L. The number that matters is not "how much am I up" but "how much space do I have between current equity and the drawdown floor." Know this number before every session.
3. After a new equity high, reduce size. When you set a new account high, recognize that your buffer is now at maximum and the floor just rose. Any reversion hurts. Either take a day off or trade lighter until the P&L stabilizes.
4. Never let one trade threaten a significant portion of your buffer. If you have $1,500 of buffer remaining and you're sizing a trade with $400 of risk, that's 27% of your remaining cushion on one setup. That's too much. A standard guideline is no more than 10-15% of remaining buffer per trade.
5. Flat days have value. In a trailing drawdown structure, a $0 day protects your buffer. Don't feel compelled to trade if conditions are poor. The floor doesn't drop when you're flat.
Here's a simple framework to keep yourself honest. Before each trade, calculate what percentage of your remaining buffer you're risking.
If your account is at $51,200 and the floor is at $49,500, your buffer is $1,700. A $300 trade risk is 17.6% of buffer. That's borderline aggressive for a prop combine. At $150 risk, you're at 8.8% — much safer.
Position sizing tools like EdgeSizer help you calculate the trade risk side of this equation precisely. Once you know the exact dollar risk per trade, you can check it against your buffer before pulling the trigger.