Position Size Calculator for Any Market

A repeatable pre-trade routine

Consistency comes from doing the same five things before every order, in the same order. The calculator is step four, not step one — it converts a plan that already exists into an order size.

• Pick the level that invalidates your idea and place the stop-loss there.
• Pick a realistic target at the next structural level, not a round number.
• Set the risk percentage you use for every trade and do not adjust it per setup.
• Read off the position size and the required margin.
• Check the risk/reward ratio clears your minimum before you send the order.

Long and short positions are not mirror images in practice

The arithmetic is symmetrical: a short with the stop the same distance above entry produces the same size and the same maximum loss. The trading reality is not. Short positions carry borrow costs on stocks, funding rates on perpetual crypto contracts, and unbounded theoretical loss above entry, which is exactly why a hard stop matters more on the short side.

The calculator enforces the correct geometry — stop above entry and target below it for shorts — so a mistyped price shows as a validation message rather than a silently wrong size.

Position size versus position value

Position size is a quantity: shares, units or coins. Position value is that quantity priced at your entry, and it is what determines margin and exposure. Small risk can coexist with very large exposure when the stop is tight, which is how traders get surprised by margin calls on a trade they thought was conservative.

The results panel shows both numbers plus the account-exposure multiple so the two never get confused.

The core position sizing formula

The entire calculator reduces to one relationship: position size equals the risk amount you accept divided by the distance between your entry and your stop-loss. The market decides where the stop belongs; the formula decides the size that keeps the loss constant.

• Risk amount = account balance × risk % ÷ 100
• Risk per unit = |entry price − stop-loss price|
• Position size = risk amount ÷ risk per unit = (balance × risk %) ÷ (entry − stop)
• Position value = position size × entry price
• Required margin = position value ÷ leverage

Worked example — stocks

A $10,000 account following the 1% rule accepts a loss of $100 on any single idea. With support at $145 and a planned long entry at $150, the risk per share is $5, so the position size is $100 ÷ $5 = 20 shares. Position value is 20 × $150 = $3,000, and a take-profit at $165 makes the reward per share $15 — a risk/reward ratio of exactly 3:1 and a break-even win rate of 25%.

Worked example — forex pips, lots and pip value

Forex is sized in lots: a standard lot is 100,000 units, a mini lot 10,000 and a micro lot 1,000. A pip is 0.0001 of price for most pairs and 0.01 for pairs quoted in yen. On a dollar-quoted pair a standard lot is worth $10 per pip, so a long entered at 1.1000 with a stop at 1.0950 is a 50-pip stop worth $500 of risk per standard lot. With $100 of risk on a $10,000 account the answer is 0.2 standard lots — 2 mini lots or 20 micro lots. A 0.01 pip size instead of 0.0001 would mis-state the stop a hundredfold, which is why the calculator exposes the pip-size selector.

Worked example — crypto volatility, precision and leverage

Crypto stops are often wide, and the formula handles that automatically: a wider stop produces a smaller coin quantity instead of a larger loss. On Bitcoin at $65,000 with a 6% stop at $61,100, the risk per coin is $3,900, so $100 of risk sizes a position of 0.0256 BTC worth about $1,666; at 10× leverage the isolated margin is roughly $167. For tokens priced in fractions of a cent the calculator keeps eight decimals so results in tens of millions of units do not collapse into rounding error, and it flags when required margin exceeds your balance.

Understanding the calculator's outputs

Position value is the total notional exposure — units multiplied by entry — and can be many times your balance while your risk stays small, so it must be read separately. Required margin is the collateral your broker locks up, equal to position value divided by leverage; it is not the amount you can lose. Maximum loss is the risk amount itself, balance multiplied by risk percentage, while total risk over a losing streak can stack if several correlated trades are sized off the same percentage. The R:R ratio is reward per unit divided by risk per unit and must be read against the break-even win rate of 100 ÷ (1 + R:R). Stop distance is the gap between entry and stop, shown as pips for forex and as a percentage for stocks and crypto.

Risk management best practices

Most professional traders risk 0.5% to 2% of account equity per trade, held constant across winners and losers. One percent risk costs roughly 9.6% of the account after ten straight losses — painful but recoverable. Leverage sets the margin, not your risk: a 10× account and a 1× account holding the same position lose the same dollars on the same move; leverage only changes the cash locked up and the liquidation price. Risking more than 5% per trade is the fastest reliable route to a terminal drawdown, because losses recover asymmetrically: a 50% drawdown needs a 100% gain to break even.