Position sizing and the 1% rule, with worked math

Position sizing means choosing how big a trade is from how much you are willing to lose, not from how sure you feel. The formula is position size = amount at risk divided by distance to your stop. Under the 1% rule, a $2,000 account risks $20 per trade, so a stop 2% away allows a $1,000 position and a stop 5% away allows $400.

The 1% is what you lose, not what you buy

The most common misreading of the 1% rule is "put 1% of the account into each trade." On $2,000 that would mean $20 positions, too small to teach you anything. The rule caps the loss instead. If the trade hits your stop, the account should be down about 1% and no more.

Two numbers set the size of every trade:

• Amount at risk: account balance times your risk percentage. On $2,000 at 1%, that is $20.
• Distance to stop: how far price must move against you before your stop-loss closes the trade, either as a percentage of entry or as a price per unit.

Divide the first by the second:

Position size = amount at risk / distance to stop

In dollars of exposure, $20 / 2% = $1,000. In units, $20 / $1.00 per share = 20 shares. Same trade, written two ways.

The stop comes first. Decide where the trade idea is proven wrong (under a recent swing low, below a support level), then work out the size. Stop placement has its own page: stop-loss and take-profit.

Two trades on a $2,000 paper account

Both examples are hypothetical: an ETF priced at $50, an account of $2,000, and a 1% risk budget of $20.

Stop 2% away

You buy at $50.00 and place the stop at $49.00. The distance is $1.00 per share, which is 2% of the entry.

• Shares: $20 / $1.00 = 20
• Position value: 20 x $50 = $1,000
• Loss if stopped out: 20 x $1.00 = $20, which is 1% of the account

Half the account is in the trade. Only 1% of it is at risk.

Stop 5% away

Same entry, but this time the chart says the idea is only wrong below $47.50, where the last swing low sits. The distance is $2.50, or 5%.

• Shares: $20 / $2.50 = 8
• Position value: 8 x $50 = $400
• Loss if stopped out: 8 x $2.50 = $20

The wider stop got a smaller position, and the loss at the stop is identical. That is the whole mechanism. Markets that swing hard, like crypto, tend to need wider stops and so get smaller positions. A quiet market with a tight, logical stop gets a bigger one. Your dollar risk stays flat across all of them, which is what makes one trade's result comparable to the next.

When the formula asks for more money than you have

Tighten the stop in the example above to 0.5% ($49.75) and the formula wants $20 / 0.5% = $4,000 of exposure. That is twice the account.

You have three honest choices. Accept a smaller risk (a $2,000 position with a 0.5% stop risks $10). Move the stop to a level that actually means something on the chart. Or skip the trade. Borrowing the difference with leverage makes the numbers fit, but it adds margin and liquidation risk on top of the trade itself.

Very tight stops also cost more in practice than they look on paper. Ordinary noise hits them more often, so a trade that risks less per attempt can cost more across ten attempts.

Ten losses in a row at 1% versus 10%

Long losing streaks happen even to strategies that make money, because that is how randomness behaves. Flip a fair coin 200 times and you will usually find six or more tails in a row somewhere in the sequence. A strategy that wins half its trades has the same losing streaks, and one that wins four trades in ten has longer ones.

Here is a hypothetical $2,000 account taking 10 straight losses, each time risking a fixed fraction of whatever the balance is at that moment:

• 1% per trade: $2,000 becomes $1,808.76. That is 9.6% down, and a 10.6% gain gets you back to where you started.
• 10% per trade: $2,000 becomes $697.36. That is 65.1% down, and you now need a 186.8% gain just to break even.
• A flat $200 per trade (10% of the starting balance, never adjusted): the account is at zero after the tenth loss.

Two things protect the 1% account. Each loss shrinks the next bet, so the tenth loss costs $18.27, not $20. And recovery math is lopsided: a 10% loss needs an 11.1% gain to repair, while a 50% drawdown needs 100%. At 1% per trade you stay in the zone where losses are cheap to recover. At 10% per trade, six losses leave the account down 46.9% and needing an 88.2% gain.

The arithmetic leaves out the human part. Down 9.6%, following your plan is still easy. Down 65%, the pull is to size up and win it back quickly, which is how a bad month turns into an empty account. The trading psychology guide covers that pull in more detail.

Choosing your own percentage

1% is a convention, not a law. The range you will see most often is 0.5% to 2% per trade. Beginners belong at the low end, because a strategy with no track record has an unknown win rate and unknown streaks.

Some situations argue for going lower than you planned:

• Positions that move together. Long Bitcoin and long Ethereum at 1% each behaves more like one 2% bet than two separate ones.
• Stops that might not fill at their price. In a fast market or across a price gap, the exit can land well past the stop. That slippage can turn a planned 1% loss into 1.5% or worse.
• A new strategy or a new market. Cut size until you have a few dozen trades of evidence.

Risk size only covers the losing side. The risk/reward ratio covers the winning side. Risk 1% with a target twice as far away as your stop, and a winner adds roughly 2%. At that ratio, a strategy that wins 40% of its trades comes out ahead before costs (0.4 x 2 minus 0.6 x 1 is a gain of 0.2 units of risk per trade), while one that wins 30% loses slowly.

Habits that quietly break the rule

A risk rule on paper and a risk rule in practice drift apart through small exceptions:

• Moving the stop further away after entry. Your size was calculated for the original stop. A wider stop on the same size means more than 1% at risk.
• Adding to a losing trade. Every add raises the loss at the stop.
• Sizing off the starting balance after a drawdown. After a few losses, 1% of $1,800 is $18, not $20. Recalculate from the current balance before each trade.
• Rounding up. If the formula says 8.4 shares, buy 8.
• Treating leverage as extra room. Leverage changes how much margin you post, not what you lose at the stop. Size times the dollar distance to the stop is still the loss, provided the liquidation price sits beyond your stop.

Practicing the calculation until it is automatic

With practice, sizing a trade takes well under a minute. Getting there takes repetition, and repeating it with real money is an expensive way to learn.

Alphacent starts every account with $2,000 in paper money, the same balance used on this page. Free trades use a fixed $1,000 position size, so on the free plan you run the formula in reverse: set the stop first, then check what $1,000 at that distance puts at risk (a stop 2% away risks $20, a stop 5% away risks $50). Before each paper trade, write down four things: entry, stop, dollar risk and the size the formula gives. After 20 trades, compare the loss you planned on each losing trade with the loss you actually took. If the real numbers run bigger, one of the habits above is leaking. On the free plan you close the trade yourself when price reaches your stop level. Stop-loss orders and choosing your own size ($500 to $10,000) are Pro features in the app.

Worked examples on this page use a hypothetical paper account and are for learning only, not advice. In Alphacent, free trades use a fixed $1,000 size; choosing your size, stop-loss and take-profit orders, and leverage are Pro features.

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