What Position Sizing Actually Controls
Two numbers define a trade's risk: how far your stop is from your entry, and how many units you hold. Position sizing locks the second so you control the first thing that matters — the dollars at stake. The goal isn't to guess direction better. It's to make sure that being wrong, which you will be often, stays survivable.
The standard discipline is the 1% rule: risk no more than 1% of your account on any single trade. Some traders run 2% when conviction is high, some run 0.5% while learning. The exact number is yours. The principle isn't: the loss on any one trade is small enough that a losing streak is an annoyance, not an extinction event.
The Formula
Position size = (account × risk %) ÷ (entry − stop)
That's it. The numerator is the dollars you're willing to lose. The denominator is the dollars you lose per unit if the stop hits. Divide and you get the number of units that makes the trade risk exactly what you decided.
Account $10,000, risking 1% = $100. You're long at $50 with a stop at $48, so your risk per coin is $2. $100 ÷ $2 = 50 coins, a $2,500 position. If the stop fires you lose $100 — full stop, regardless of leverage or how hard price moved.
Want a tighter stop at $49.50? Risk per coin drops to $0.50, so you'd hold 200 coins for the same $100 risk. Tighter stop, bigger position, identical dollar risk. The position size calculator does this instantly, but knowing the mechanics keeps you honest.
The dollar risk is fixed by you, not by the chart. A tighter stop lets you hold more units for the same loss; a wider stop forces fewer. The figure you protect is always the same $100.
Position size from a fixed $100 risk (varies by stop distance, $50 entry)
Why This Is Where Accounts Die
Most blow-ups aren't from a bad strategy. They're from a good strategy run at a size that can't survive variance. A trader with a real edge and a 55% win rate will still hit five losers in a row eventually — that's just probability. At 1% risk, five straight losses is a 5% dip you barely feel. At 10% risk per trade, the same streak is a 50% drawdown that needs a 100% gain to undo, and by then the trader is tilted, oversizing to "make it back," and finishing the job.
Leverage makes this worse because it disguises the real exposure. A "small" 0.5 BTC position at 20x is the risk of a 10 BTC spot position. Size off the dollars at risk to your stop, never off the notional or the leverage number — those lie to you about how much you actually stand to lose.
| 1% Risk Per Trade | 10% Risk Per Trade | |
|---|---|---|
| Loss on one trade | ✅ 1% — barely felt | ⚠️ 10% — stings every time |
| Five losers in a row | ✅ ~5% dip | ❌ ~50% drawdown |
| Gain needed to recover that streak | ✅ ~5% | ❌ 100% |
| Survives normal variance? | ✅ Yes — designed to | ❌ No — one streak ends it |
| Room to stay disciplined | ✅ Losses stay boring | ❌ Tilt, revenge-size, blow up |
How a Journal Exposes Sizing Mistakes
The tell is in the variance of your losses. If your trades are sized correctly, your losing trades should cost roughly the same — your planned risk, over and over. When they don't, when some losses are 3x or 5x others, you're sizing by emotion: bigger when you're confident or chasing, smaller when you're scared.
Tradermake.money imports every fill and shows the actual loss on each closed trade, so the inconsistency is impossible to hide. The PnL tracker charts your real per-trade results, and the AI coach calls out the oversized trades and the days you abandoned your own rule. Consistent sizing is visible as a flat band of losses; chaos shows up as spikes.