Lot Size Calculator

How lot size works

A lot is a standard unit of currency traded. A standard lot is 100,000 units of the base currency, a mini lot is 10,000 units (0.1 standard lot), and a micro lot is 1,000 units (0.01 standard lot). Lot size sets how much each pip move is worth. The trade's risk is set by three things: the lot size, the stop loss in pips, and the pip value.

The formula is: lots = risk in dollars ÷ (stop in pips × pip value per standard lot). Rearranged, the loss at that size equals the stop in pips times the pip value times the lots, so it lands on your risk amount.

What a pip is worth

For most pairs quoted against the US dollar, such as EURUSD, GBPUSD, AUDUSD and NZDUSD, one pip (0.0001) on one standard lot is worth $10. For USD-base pairs such as USDCAD, USDCHF and USDJPY, the pip value in dollars changes with the price, so the calculator asks for the current price. Brokers may quote a different contract size or pip definition, so check the value on your own platform. The override field lets you enter it directly.

Worked example

Take a $10,000 account, 1% risk and a 25-pip stop on EURUSD. Risk is 1% × $10,000 = $100. Each standard lot risks 25 pips × $10 = $250 at that stop. Lots = $100 ÷ $250 = 0.40 standard lots. That is 4.00 mini lots, 40.0 micro lots, or 40,000 units. At 0.40 lots the loss is 0.40 × $250 = $100, exactly your risk.

If the stop were 50 pips instead, the same $100 risk would support only 0.20 standard lots. Wider stops mean smaller size, and the dollar risk stays fixed.

Using it with a prop firm daily loss limit

Prop firm accounts often have a daily loss limit, for example 5% of the starting balance, in addition to a maximum drawdown. Size each trade so that a full stop-out leaves room under the daily limit. On a $50,000 account with a 5% daily limit ($2,500), risking 1% per trade means a stop-out costs $500, so you could take several losing trades before reaching the limit. Remember that open trades can lose more than planned before they close, and a single gap or slippage event can exceed your stop.

Common mistakes

• Sizing by feel, then moving the stop. Choose the stop from your setup first, then size the lot.
• Mixing up pips and points, or assuming every pair has the same pip value. JPY pairs use 0.01 as the pip, not 0.0001.
• Forgetting that rounding down protects you. Rounding up to the next lot increases risk above the planned amount.
• Using the account balance instead of the risk amount. Risk % should be taken from the balance you can actually lose, after the day's open profit or loss.

Frequently asked questions