Free trading calculator

Position Size Calculator

Calculate how many shares, coins, or price-based units fit your planned risk. Enter your account balance, risk percentage, entry price, and stop-loss price to estimate your maximum loss and position size before placing a trade.

Maximum risk
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Price risk per unit
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Position size
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Position value
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Important: This calculator assumes that both your account and the instrument’s quoted price are in USD and that profit or loss changes dollar-for-dollar with each unit. Forex lots, futures, options, CFDs, and leveraged contracts can use different contract sizes and pip or tick values. For those instruments, confirm the result with your broker’s specifications and the UCharts pip calculator.
Position sizing formula

How the calculator determines position size

The calculation limits the planned loss to a percentage of your account balance. It does not predict whether a trade will win, account for gaps or slippage, or guarantee that an order will close at the stop price.

1. Maximum risk
Account balance × risk percentage
2. Price risk per unit
Absolute value of entry price − stop price
3. Position size
Maximum risk ÷ price risk per unit
How to use it

Five steps to calculate a position

Define the trade and its invalidation level before calculating size. The calculator should be the final step in planning, not a substitute for a trading plan.

01
Enter account balance
Use the capital available in the account, not the buying power offered through leverage.
02
Choose risk percentage
Use a level that fits your own plan, experience, and ability to tolerate losses.
03
Enter planned entry
Add the price at which you expect the position to be opened.
04
Enter stop-loss price
Use a price that invalidates the trade idea rather than an arbitrary distance.
05
Round the result down
Use the nearest supported share or unit increment without exceeding the calculated size.
Worked examples

Position size calculation examples

These simplified examples assume a USD account and an instrument quoted in USD. Fees, spreads, slippage, taxes, and leverage are excluded.

Stock — long
Standard equity trade
Balance: $10,000
Risk: 1% = $100
Entry: $100 | Stop: $95
Risk per share: $5
20 shares
ETF — short
Stop above the entry
Balance: $25,000
Risk: 0.5% = $125
Entry: $500 | Stop: $505
Risk per share: $5
25 shares
Crypto — long
Fractional Bitcoin position
Balance: $20,000
Risk: 2% = $400
Entry: $105,000 | Stop: $103,000
Risk per BTC: $2,000
0.20 BTC
Small account
Conservative example
Balance: $1,000
Risk: 0.5% = $5
Entry: $50 | Stop: $48
Risk per share: $2
2.5 shares*

*If fractional shares are unavailable, round down to two shares. Never round up beyond the calculated position size.

Risk management

The mathematics of a 1% risk example

Using a constant percentage means position risk decreases as the account declines. The examples below illustrate compounding; they are not a recommended risk level or a promise of performance.

Starting balance
$10,000
Illustrative account balance
1% risk example
69 losses
Approximately halves the account when compounded
5% risk example
14 losses
Takes the account below half when compounded
Breakeven at 2:1
33.3%
Before spreads, fees, slippage, and taxes

Position sizing controls the amount planned for loss; it cannot control execution. Price gaps, slippage, liquidity, leverage, and correlated positions can make realized losses larger than the calculator’s estimate.

Common mistakes

Position sizing errors to avoid

A correct formula can still produce an unsuitable trade if the inputs or assumptions are wrong.

1
Ignoring account changes
A fixed dollar amount represents a different percentage after the account grows or declines. Recalculate using the current account balance.
2
Choosing the stop to force a larger size
Set the invalidation point from the trade setup first. Moving the stop closer simply to increase size changes the trade’s logic.
3
Widening the stop after entry
Increasing stop distance after the position is open raises the planned loss unless the position is reduced at the same time.
4
Overlooking correlated exposure
Several positions influenced by the same currency, sector, or market factor can behave like one larger position during volatility.
5
Confusing units with lots or contracts
Forex, futures, options, and CFDs have contract specifications. A calculated unit count is not automatically a valid lot or contract size.
6
Forgetting trading costs
Commissions, spreads, funding costs, and slippage reduce the distance available before the maximum planned loss is reached.
FAQ

Position size calculator questions

What does a position size calculator do?

It estimates the number of shares or price-based units that fit a chosen maximum loss. The calculation uses account balance, risk percentage, entry price, and stop-loss price.

Does this calculator work for both long and short trades?

Yes. It uses the absolute difference between entry and stop prices, so the stop can be below the entry for a long trade or above the entry for a short trade.

Can I use this as a forex lot size calculator?

Not by itself. Forex results depend on the currency pair, account currency, pip value, and contract size. Use the pip calculator and confirm the final lot size against your broker’s specifications.

Why can the calculated position value exceed my account balance?

The formula limits loss at the stop; it does not limit purchase value. A position value above the account balance would require margin or leverage and may be unavailable or unsuitable. Confirm buying-power and margin requirements with your broker.

Should I round the position size up or down?

Round down to the nearest share, fractional-share increment, coin increment, or supported unit. Rounding up increases the planned loss beyond the selected risk percentage.

Does a stop-loss guarantee the calculated maximum loss?

No. A stop order can execute at a worse price because of gaps, volatility, slippage, or limited liquidity. Treat the result as an estimate rather than a guaranteed loss limit.

Related UCharts resources

These calculators and guides cover the next parts of trade planning, chart analysis, and risk evaluation.

Risk-reward calculator
Compare the planned loss with the potential reward before taking a position.
Pip calculator
Measure price movement and review pip values for forex-related calculations.
Technical analysis guide
Learn about trends, support, resistance, indicators, volume, and chart structure.
How to read stock charts
Understand price, volume, timeframes, and the chart levels used to plan entries and stops.
Stock market analysis for beginners
Explore technical, fundamental, and sentiment-based approaches to market analysis.
How traders evaluate a prop firm
Review drawdown, platform, payout, and rule considerations before paying an evaluation fee.

Educational use only: This calculator and its examples are general information, not individualized financial, investment, tax, or trading advice. Trading can result in losses, including losses beyond deposited funds when leverage is used.