The 1% Risk Rule in Trading: Formula, Examples & Position Sizing

The 1% risk rule is a simple risk-management guideline:

> Do not plan to lose more than 1% of your trading account on a single trade.

If your account is worth $10,000, 1% is $100.

That does not mean you should invest only $100.

It means the planned loss, if your stop is reached, should be around $100 before accounting for slippage, gaps, fees, and other execution differences.

The basic formula is:

Maximum risk per trade
= Account size × Risk percentage

For a $10,000 account:

$10,000 × 1%
= $100

Once you know the maximum amount you are willing to risk, you can use your entry price and stop price to calculate position size.

The 1% rule is designed to limit the damage from any single trade.

Instead of deciding position size based only on confidence, available cash, or the number of shares you want to buy, the rule starts with a maximum loss budget.

For example:

Account size = $25,000
Risk per trade = 1%

Maximum planned risk
= $25,000 × 0.01
= $250

That $250 becomes the risk budget for the trade.

You then work backward from the stop-loss distance to determine how many shares you can take.

The first calculation is:

Maximum risk amount
= Account size × Risk percentage

At 1% risk:

Maximum risk amount
= Account size × 0.01

Then calculate the risk per share:

Risk per share
= |Entry price − Stop price|

Finally:

Position size
= Maximum risk amount ÷ Risk per share

These three steps connect your account size, stop distance, and position size.

Suppose:

Account size = $10,000
Risk per trade = 1%
Entry price = $50
Stop price = $47.50

Step 1: Calculate the Maximum Risk

$10,000 × 1%
= $100

Your planned maximum risk is $100.

Step 2: Calculate Risk per Share

$50 − $47.50
= $2.50

You are risking $2.50 per share.

Step 3: Calculate Position Size

$100 ÷ $2.50
= 40 shares

The risk-based position size is 40 shares.

The position value would be:

40 × $50
= $2,000

Notice the difference:

Position value = $2,000
Planned risk = $100

The 1% rule limits the planned loss, not the total amount invested in the position.

This is one of the most common misunderstandings.

A 1% account-risk rule and a 1% stop-loss are not the same thing.

1% Account Risk

This refers to the amount of your total account that you are willing to lose on one trade.

For a $20,000 account:

1% account risk
= $200

1% Stop-Loss

This refers to how far the stop price is from the entry price.

If you enter at $100 and place the stop at $99:

Stop-loss percentage
= 1%

Those are two different measurements.

A trade can have:

• 1% account risk with a 3% stop;
• 1% account risk with a 5% stop;
• 1% account risk with a 10% stop.

The position size changes to keep the planned dollar risk near the same level.

Suppose you have a $20,000 account and use a 1% risk limit.

Your risk budget is:

$20,000 × 1%
= $200

Now compare three trades with the same entry price but different stop distances.

The wider the stop, the smaller the position.

The narrower the stop, the larger the position.

The risk budget remains the same.

This is the core idea behind risk-based position sizing.

The 1% rule does not make losing trades disappear.

Its purpose is to prevent one loss from doing disproportionate damage to the account.

It Limits the Impact of a Single Loss

If you risk 10% of your account on one trade, one full loss is a major setback.

If you risk 1%, the same losing trade has a much smaller effect on total capital.

It Reduces the Effect of Losing Streaks

Losses often come in clusters.

If you lose five trades in a row while risking 1% of the current account value each time, the account declines gradually rather than collapsing from a small number of trades.

It Forces Position Size to Respond to Volatility

A wider stop means fewer shares.

A tighter stop means more shares.

The rule therefore discourages using the same share count on every trade regardless of volatility.

It Makes Risk Comparable Across Trades

A $5 stop on a $200 stock and a $1 stop on a $20 stock are very different in price terms.

Converting both into a dollar risk budget makes the trades easier to compare.

Suppose you start with $10,000 and risk 1% of the current account balance on each trade.

If each trade loses the full planned amount, the account changes roughly like this:

After five consecutive full-risk losses, the account would be about $9,509.90 before fees and execution differences.

That is a decline of roughly 4.9%, not 5% exactly, because the 1% amount gets smaller as the account balance falls.

This is one reason percentage-based risk controls can slow the pace of drawdowns.

Some traders use a fixed dollar amount instead of recalculating a percentage every time.

For example:

Maximum risk per trade = $100

This is simple, but the risk percentage changes as the account value changes.

If the account is $10,000:

$100 = 1%

If the account falls to $8,000:

$100 = 1.25%

If the account grows to $20,000:

$100 = 0.5%

Using a percentage keeps risk proportional to account size.

Using a fixed dollar amount keeps the number simple.

Neither approach removes market risk, but they behave differently as the account changes.

The answer depends on how you define your trading capital.

Some traders calculate risk from total account equity.

Others use only the capital specifically allocated to a strategy.

For example, imagine you have:

Brokerage account value = $50,000
Capital allocated to active trading = $20,000

If your rule is based on the active-trading allocation:

1% of $20,000
= $200

If it is based on total account equity:

1% of $50,000
= $500

The important part is consistency.

Changing the denominator from trade to trade makes the risk rule less meaningful.

No.

The 1% figure is a rule of thumb, not a universal law.

Some traders use less than 1%, especially when:

• trading highly volatile stocks;
• holding positions through earnings;
• trading illiquid securities;
• running multiple correlated positions;
• experiencing a drawdown;
• testing a new strategy.

Others may use more than 1%, but larger risk percentages increase the impact of losses and losing streaks.

The useful question is not whether 1% is “correct.”

It is whether your risk level is small enough that one trade cannot materially damage the account.

Suppose you have a $20,000 account.

Now assume each trade has a $4 risk per share.

The risk percentage directly changes position size.

Doubling the risk percentage from 1% to 2% doubles the planned dollar risk and, with the same stop distance, doubles the share count.

The 1% rule usually refers to risk per trade, not total portfolio risk.

If you have five open trades and each can lose 1% of the account, your total planned open risk may be much larger than 1%.

For example:

5 positions × 1% risk each
= 5% gross planned risk

That does not necessarily mean all five positions will lose at the same time.

But if the positions are highly correlated, the risks can become concentrated.

For example, holding several semiconductor stocks may look like several separate trades, but they may react similarly to the same industry news.

This is why per-trade risk and portfolio-level risk should be considered separately.

Imagine you hold:

• one semiconductor stock;
• another semiconductor stock;
• a semiconductor ETF;
• a leveraged semiconductor ETF.

If each position carries 1% planned risk, the portfolio may still behave like one large concentrated bet.

A risk limit per trade does not automatically create diversification.

You should also consider whether several positions depend on the same market factor, sector, macro event, or earnings theme.

A stop-loss price is not a guaranteed exit price.

Suppose:

Account size = $10,000
Planned risk = 1% = $100
Entry = $50
Stop = $48
Position size = 50 shares

The planned risk is:

50 × $2
= $100

But if the stock gaps down and the actual exit happens at $46:

50 × $4
= $200

The actual loss would be 2% of the original account, not 1%.

This is especially relevant around:

• earnings;
• major economic data;
• regulatory announcements;
• biotech trial results;
• overnight news;
• illiquid stocks.

The 1% rule controls planned risk, not guaranteed maximum loss.

Slippage occurs when the actual execution price differs from the expected price.

Suppose your planned risk is exactly $100.

A small amount of slippage may push the actual loss to $105 or $110.

That does not automatically mean the risk process failed.

It means the real market introduces execution costs that a simple formula cannot perfectly predict.

If slippage is consistently material, one approach is to size the position slightly below the mathematical maximum.

Usually, if the calculation gives a fractional or awkward number of shares, rounding down is the more conservative choice.

Suppose:

Risk budget = $100
Risk per share = $3.20

Then:

$100 ÷ $3.20
= 31.25 shares

If you are trading whole shares, 31 shares keeps planned price risk below $100:

31 × $3.20
= $99.20

Rounding up to 32 shares would produce:

32 × $3.20
= $102.40

That exceeds the original risk budget.

Suppose:

Account size = $30,000
Risk percentage = 1%
Entry = $120
Stop = $111

Maximum risk:

$30,000 × 1%
= $300

Risk per share:

$120 − $111
= $9

Position size:

$300 ÷ $9
= 33.33 shares

Using whole shares, you could round down to 33:

33 × $9
= $297 planned price risk

The position value would be:

33 × $120
= $3,960

Again, the position value is much larger than the risk amount.

Suppose:

Account size = $30,000
Risk percentage = 1%
Entry = $120
Stop = $118

Maximum risk is still:

$300

Risk per share is now:

$2

Position size becomes:

$300 ÷ $2
= 150 shares

Position value:

150 × $120
= $18,000

The stop is tighter, so the formula allows a much larger position.

But the trade now has more exposure to:

• ordinary price noise;
• slippage;
• liquidity constraints;
• gap risk;
• transaction costs.

This is why position-size math should not be separated from the quality of the stop level itself.

A simple workflow looks like this:

1. Determine the account balance or capital allocation you use for risk calculations.
2. Multiply it by your chosen risk percentage.
3. Define your entry price.
4. Define the stop price based on the trade idea.
5. Calculate risk per share.
6. Divide the maximum risk amount by risk per share.
7. Round down if needed.
8. Check whether the resulting position is practical given buying power, liquidity, and portfolio concentration.
9. Reassess if the trade involves unusual gap or event risk.

In formula form:

Account size
× Risk %
= Maximum risk amount

Then:

|Entry − Stop|
= Risk per share

Then:

Maximum risk amount
÷ Risk per share
= Position size

You can also use the BasisPilot Position Size Calculator to calculate the share count directly.

For the stop-distance calculation itself, see How to Calculate Stop-Loss Percentage.

What is the 1% rule in trading?

The 1% rule means limiting the planned loss on a single trade to about 1% of your account or designated trading capital.

For a $10,000 account, 1% is $100.

How do I calculate 1% risk?

Use:

Account size × 0.01

For example:

$15,000 × 0.01
= $150

Does the 1% rule mean I can only invest 1% of my account?

No.

It refers to planned loss, not position value.

You may hold a position worth much more than 1% of the account while still limiting the planned loss to about 1%.

Is a 1% risk rule the same as a 1% stop-loss?

No.

A 1% risk rule refers to account-level loss.

A 1% stop-loss refers to the percentage distance between entry price and stop price.

Can I still lose more than 1%?

Yes.

A stop order may execute below or above the planned price because of gaps, slippage, volatility, liquidity, or fast markets.

The 1% rule controls planned risk, not guaranteed maximum loss.

Is 2% risk per trade too much?

There is no universal threshold that is appropriate for everyone.

But moving from 1% to 2% doubles the planned loss per trade and increases the impact of losing streaks.

Should I reduce risk after losses?

Some traders reduce their risk percentage during drawdowns, while others keep the same percentage and allow the dollar risk amount to fall naturally as account equity declines.

The important point is to use a rule that is consistent and small enough to keep losses manageable.

The 1% rule is not about predicting which trades will win.

It is about controlling how much damage one losing trade can do.

The core calculation is:

Maximum risk
= Account size × Risk percentage

Then:

Position size
= Maximum risk ÷ Risk per share

Used consistently, this approach turns position sizing into a repeatable risk decision rather than a guess based on confidence or available cash.