How do I calculate lot size in forex?

Multiply your account balance by the percentage you want to risk, then divide by the stop-loss distance in pips times the pip value per lot. For example $10,000 × 1% = $100; $100 ÷ (50 pips × $10 per lot) = 0.20 lots on EUR/USD with a USD account.

Should I round the lot size up or down?

Down. Rounding up to the broker's lot step means risking more than planned. If the rounded size is zero, the trade is too large for your account at that stop distance.

Position Size Calculator (Lot Size) for Forex

Inputs

Account balance

Risk per trade (%)

Account currency

Currency pair

Stop-loss distance (pips)

Distance from entry to stop-loss. Use whole pips (a 5-digit quote of 0.00250 = 25 pips).

Current price of the pair

Pre-filled with the ECB reference rate of 2 October 2026. Type in the live price from your platform for an exact result.

Conversion rate: 1 USD = ? USD

Broker lot step

Leverage (optional)

Results

Enter valid numbers to see the result. The calculator updates as you type.

Calculator limits

Results are arithmetic on the numbers you enter, not trading advice. Brokers may use different contract sizes (especially for exotic pairs and CFDs), round lot sizes differently and convert profits at their own rates. Leveraged forex and CFD trading carries a high risk of losing money quickly; most retail CFD accounts lose money. Check your broker's contract specification before you trade.

The position size formula

Units = (Account balance × Risk %) ÷ (Stop-loss in pips × Pip value per unit)
Lots = Units ÷ 100,000

The calculator works out the pip value per unit for your pair and account currency (see the pip value calculator), then finds the size at which a stop-loss hit loses exactly your chosen percentage. It then rounds down to your broker's lot step, so the real risk is never higher than planned.

Worked example — EUR/USD, USD account

Balance $10,000, risk 1% = $100. Stop-loss 50 pips. EUR/USD pip value = $0.0001 per unit ($10 per standard lot).

Units = $100 ÷ (50 × $0.0001) = 20,000 units = 0.20 lots. If the stop is hit, 50 pips × $2 per pip = $100.

Worked example — USD/JPY, USD account

Balance $5,000, risk 2% = $100. Stop 40 pips. USD/JPY at 150.00, so 1 pip on 1 unit = 0.01 ÷ 150 = $0.0000667.

Units = $100 ÷ (40 × 0.0000667) ≈ 37,500 units = 0.375 lots → 0.37 lots after rounding down (actual risk ≈ $98.67).

Small accounts

With a small balance the correct size is often below the 0.01-lot minimum. For example, risking 1% of $200 ($2) with a 30-pip stop on EUR/USD needs 0.0067 lots — less than one micro lot. The honest options are a tighter (but still logical) stop, a broker that allows smaller sizes, or not taking the trade. Our guide to position sizing for $100–$1,000 accounts has full tables.

What the calculator does not know

Slippage and gaps. A stop-loss becomes a market order; around news or weekend gaps it can fill worse than the stop price, so the loss can exceed the planned amount.
Spread and commission. Add them to the stop distance if you want the planned risk to include costs.
Correlated positions. Two trades on EUR/USD and GBP/USD with 1% each behave much like one 2% trade.

Read the full lesson on position sizing and on risk management.

Other calculators

Last reviewed: October 4, 2026