Forex Position Size Calculator

What is forex position sizing?

Position sizing is the process of deciding how big a forex trade should be (measured in lots or units) given how much of your account you are willing to lose if the trade hits its stop-loss. It is the single most important risk-management step in trading. Two traders with the same edge but different position-sizing rules will end up with completely different equity curves: one survives a drawdown streak, the other blows up.

Position-size formula

The standard formula used by professional traders, prop firms and brokers is:

Position Size (lots) = (Account × Risk%) ÷ (Stop Loss pips × Pip Value per lot)

• Account: your account balance in the account currency (e.g. $10,000 USD).
• Risk %: the fraction of the account you are willing to lose if the stop is hit (typically 0.5 to 2%).
• Stop Loss pips: distance from entry to stop-loss, in pips.
• Pip Value per lot: depends on the pair and your account currency. For most USD-quoted majors, 1 pip on a standard lot (100,000 units) ≈ $10.

Worked example: EUR/USD, 1% risk

Account: $10,000 USD. Risk per trade: 1%. Pair: EUR/USD. Stop-loss: 50 pips.

• Dollar risk = $10,000 × 1% = $100
• Per-lot loss at 50 pips = 50 × $10 = $500 per lot
• Position size = $100 ÷ $500 = 0.2 lots (20,000 units, or 2 mini lots)

If the trade hits the stop, you lose $100, the pre-defined risk. Each pip against you costs $2. The calculator above does this math for you, using a pre-set pip value for each pair (JPY pairs, gold and silver differ from USD majors).

More position size examples

The formula never changes. What changes is the pip value, the balance you size from, and how honest the stop distance is. These examples use the same pip values as the calculator.

Example 2: a JPY pair (USD/JPY)

Account $5,000, risk 1%, stop 25 pips. On USD/JPY one pip is 0.01 in price, and the calculator uses about $9.1 per pip per standard lot (the exact figure moves with the USD/JPY rate).

• Dollar risk = $5,000 × 1% = $50
• Per-lot loss = 25 × $9.1 = $227.50
• Position size = $50 ÷ $227.50 ≈ 0.22 lots

Because a JPY pip is worth a little less than $10, the position is slightly larger than the 0.20 lots you would get on EUR/USD with the same risk and stop.

Example 3: gold (XAU/USD)

Account $10,000, risk 0.5%, stop $5 below entry. Most brokers quote a gold pip as $0.01, so a $5 stop is 500 pips. A standard gold lot is usually 100 ounces, which makes one pip worth $1 per lot.

• Dollar risk = $10,000 × 0.5% = $50
• Per-lot loss = 500 × $1 = $500
• Position size = $50 ÷ $500 = 0.1 lots (about 10 ounces)

Gold contract sizes vary by broker. If yours uses a different lot size or pip definition, check the pip value on the order ticket. The "units" figure in the calculator assumes 100,000-unit forex lots, so ignore it for metals.

Example 4: sizing after a drawdown

The account from example 1 has fallen to $7,500. Same 1% risk, same 50-pip EUR/USD stop.

• Dollar risk = $7,500 × 1% = $75
• Position size = $75 ÷ $500 = 0.15 lots

Keeping the old 0.2 lots would risk $100, which is 1.33% of the current balance. Sizing from the current balance shrinks positions during a losing run and grows them as the account recovers.

Example 5: adding the spread to the stop

Account $10,000, risk 1%, a 30-pip technical stop on EUR/USD, and a 2-pip spread. You pay the spread on entry, so the real distance to the stop is 32 pips.

• Sized on 30 pips: 0.33 lots. If stopped out, the loss is about $107, not $100.
• Sized on 32 pips: 0.31 lots. The loss stays at the planned $100.

Example 6: a non-USD account (GBP)

The calculator's pip values are in US dollars. Choosing a different account currency changes the symbol shown, not the pip value. For a GBP account, convert the pip value yourself. At an assumed GBP/USD rate of 1.25, $10 per pip is £8 per pip.

• Account £10,000, risk 1% = £100
• Stop 40 pips on EUR/USD: per-lot loss = 40 × £8 = £320
• Position size = £100 ÷ £320 ≈ 0.31 lots

Using the unconverted $10 pip value gives 0.25 lots, which risks about £80 instead of £100. For a GBP account the error makes you trade smaller than planned. For a JPY or ZAR account the numbers are far off, so convert before you size.

How to use this position size calculator

1. Set your account currency. This sets the currency symbol on the results. Pip values stay in US dollars, so for a non-USD account convert the pip value as shown in example 6 above.
2. Enter your account balance. Use current balance, not initial deposit. A 20% drawdown means your 1% rule should size off the drawn-down balance, not the starting amount.
3. Pick your risk per trade. Conservative (≤1%), moderate (1 to 2%), aggressive (2 to 3%). The calculator colour-codes your choice.
4. Enter your stop-loss in pips. A wider stop survives noise but forces a smaller position. A tighter stop allows a larger position but is more likely to be triggered by routine volatility.
5. Choose your currency pair. The pip value we use is pre-calibrated per pair. JPY pairs and metals have very different pip values from USD majors.

The 1% rule explained

The 1% rule says: never risk more than 1% of your account on any single trade. The math behind it is simple: even a great strategy can produce a losing streak. With a 50% win rate and 1:1 R/R you have a roughly 1% chance of 7+ losses in a row. At 1% risk per trade, that streak is a 7% drawdown, painful but recoverable. At 5% risk per trade, the same streak is a 30%+ drawdown, which requires a 43% gain to break even.

Prop firms (FTMO, MyForexFunds, The5%ers, etc.) typically require traders to never exceed 2% per trade and 5% per day. Use the calculator to verify your sizing fits the firm's risk rules before entering the trade.

Quick reference: lot size at $10,000 account, EUR/USD

How position size scales with risk % and stop-loss distance. All values assume a $10,000 USD account on a USD-quoted major with $10 pip value per standard lot.

What is a pip?

A pip ("percentage in point") is the smallest standard price move in forex. For most major pairs (EUR/USD, GBP/USD, AUD/USD) one pip = 0.0001. For JPY-quoted pairs (USD/JPY, EUR/JPY) one pip = 0.01. For gold (XAU/USD), brokers usually quote pips as 0.01 of price. The calculator already maps each pair to its correct pip value, but if you're trading with a broker that defines pips differently, recheck the pip value displayed.

Common position-sizing mistakes

• Risking too much per trade. Anything above 2% destroys the math. Even a 60% win-rate edge can't survive 5% risk during a normal losing streak.
• Using too tight a stop. A 5 to 10 pip stop on a major pair has high probability of being triggered by routine spread/noise, not by your actual thesis being wrong. Size from the stop, not the other way around.
• Ignoring spread & slippage. A 30-pip stop with a 2-pip spread is really a 32-pip risk. During news, slippage can blow stops by another 10 to 20 pips. Pad your stop and recalculate.
• Static sizing during drawdown. If you started at $10,000 and you're now at $7,500, sizing 1% off the original $10,000 means you're actually risking 1.33% of current equity. Always size off current balance.
• Cross-pair pip-value drift. The pip values used here are approximate. For a non-USD account or exotic pairs, the live pip value depends on the cross rate, which moves constantly. Recheck before sizing large positions.

Position sizing for prop-firm traders

Funded-account traders (FTMO, The5%ers, MyForexFunds, etc.) operate under stricter rules than retail: typical drawdown limits are 5% daily and 10% trailing. The 1% rule effectively becomes 0.25 to 0.5% per trade because you need to absorb both your own losses and an unfavourable streak without breaching either limit. Plug in the prop-firm account size, set risk to 0.5%, and never increase size to chase payout targets. The funded account's rules will reset every loss to zero.

Related tools and concepts

• Economic Calendar - never size up before a high-impact news release without widening your stop.
• Percentage Calculator - quick math for win-rate, risk-of-ruin, and break-even R/R calculations.