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Risk & position sizing

Position Size Calculator

Size a trade from balance, risk and stop distance, for forex, stocks, crypto, futures and indices. Most calculators stop at the lot size. This one also prices the costs into the size, shows the margin it demands, and tells you what the trade does to your expectancy and drawdown.

The trade
Stop defined by
Costs, leverage, edge
The size
Position size
0.49 lots
48,733 units
Risk if stopped
$250
1.00% of balance
Stop distance50.0 pips
Notional exposure$56,774
Margin required$1,892
Effective leverage2.3 : 1
Round-turn cost$6.34
Cost as share of risk2.5% of risk
Risk / reward1 : 2.00
Profit at target, after costs$481
Break-even win rate33.3%
Expectancy at your win rate0.35R per trade
Losses in a row to −20%23 losses
USD account. Pip value $10 per standard lot. Spread and commission are subtracted from the risk budget before sizing.
Save this plan and it feeds your expectancy, drawdown and risk-of-ruin statistics. Save to dashboard

The formula

Position size is the only variable that lets you fix the loss in advance. Choose the loss first, measure the distance to the stop, then divide.

risk amount = balance × risk %
stop distance = | entry − stop |
value per unit = pip value, or 1 per point
size = (risk amount − costs) ÷ (stop distance × value per unit)

The subtraction is the part most calculators leave out. If spread and commission come out of the same pot as the stop, the size that risks exactly 1% is smaller than the naive answer.

Worked example

A $25,000 account, 1% risk, long EUR/USD at 1.1650, stop 1.1600, target 1.1750, 0.6 pip spread, $7 per lot round turn.

risk amount25,000 × 1% = $250
stop distance0.0050 = 50 pips
value per pip$10 per standard lot
naive size250 ÷ 500 = 0.50 lots
cost-adjusted size250 ÷ 513 = 0.487 lots

Half a lot is 50,000 units of base currency: about $58,250 of exposure against $250 of accepted risk. The exposure is large, the loss is bounded, provided the stop is honoured.

What this one does that a lot-size calculator does not

Cost-adjusted

Spread and commission come out of the risk budget before the size is computed, not after.

Volatility stops

Define the stop as an ATR multiple and the size adjusts with conditions instead of your mood.

Margin and leverage

The size that is affordable on margin is not the size that is sane on risk. Both numbers are shown.

Edge, not just size

Break-even win rate, expectancy at your own hit rate, and how many losses in a row reach −20%.

Every market

Forex in pips including JPY pairs, and stocks, crypto, indices and futures in price units.

Assumptions this calculator makes

Account currency is USD
Non-USD accounts need the pip value converted at the current rate.
One standard lot is 100,000 units
Mini lots are 10,000 and micro lots 1,000 units.
JPY pip value uses the entry price
For JPY-quoted pairs a pip is 0.01, worth 1,000 ÷ price per lot.
Slippage is not modelled
A gap through your stop can produce a larger loss than calculated.
Expectancy assumes your inputs hold
It applies the win rate you typed to this trade's reward-to-risk, nothing more.
Nothing here is a forecast
The calculator quantifies one trade under your inputs. It does not predict profit.

Frequently asked

How much should I risk per trade?

Most systematic traders size between 0.25% and 2% of equity. The right number follows from your strategy's expectancy and drawdown profile, not from preference. Run it through the risk of ruin and drawdown calculators before committing.

Why is your lot size smaller than other calculators?

Because spread and commission are subtracted from the risk budget first. Set both to zero and the number matches the standard formula exactly.

Should position size change with volatility?

If the stop is volatility-based it already does. Choose the ATR multiple mode: a wider stop in volatile conditions gives a smaller size at the same risk. See ATR Calculator.

Why is margin different from risk?

Margin is collateral against the notional exposure. Risk is the loss you accept if the stop is hit. They are unrelated numbers, and a size that is affordable on margin can still be reckless on risk. See Margin Calculator.

Does it work for stocks and crypto?

Yes. Pick the market and the output becomes a share, coin or contract count. The arithmetic is identical, only the value per unit changes.

What if the size is below my broker's minimum?

Then the trade is too large for the account at that stop distance. Widen the account, tighten the stop, or skip the trade. Do not round the size up.

Related tools

All tools →
Risk/Reward Calculator Break-even win rate for a given ratio. Stop Loss Calculator Stop distance from risk and a fixed size. Pip Calculator Pip value for the pair you are sizing. Risk of Ruin Calculator Whether that risk level survives a losing run.

Keep the plan, then measure what it did.

Saved trades feed your expectancy, drawdown and risk of ruin, so the next size is set by evidence rather than habit.