Most blown accounts do not come from bad entries. They come from a lot size picked by feel. If you know how to calculate lot size in forex, every trade risks the same, small, planned amount, whether you trade EURUSD, USDJPY or gold.
This guide gives you one formula, four worked examples and a checklist of mistakes to avoid. If you just want the answer for a trade right now, use our position size calculator and come back to learn why it works.
What lot size actually means
A lot is the trade size in forex. On most brokers:
| Lot type | Size | Typical pip value on a USD-quoted pair |
|---|---|---|
| Standard lot (1.00) | 100,000 units of the base currency | about $10 per pip |
| Mini lot (0.10) | 10,000 units | about $1 per pip |
| Micro lot (0.01) | 1,000 units | about $0.10 per pip |
The bigger the lot, the more every pip is worth, for you and against you. Lot size is the only part of a trade that you fully control, so it is where risk management starts.
Contract sizes are not identical everywhere. Check the symbol’s Specification in MetaTrader (right-click the symbol in Market Watch) before you trust any example, including ours.
The lot size formula
Lot size = Risk amount ÷ (Stop loss in pips × Pip value per 1 lot)
Each part is simple:
- Risk amount: account balance × risk percentage. A $10,000 account risking 1% is $100.
- Stop loss in pips: the distance from your entry to your stop, taken from the chart, not guessed.
- Pip value per 1 lot: what one pip is worth in your account currency for a full 1.00 lot. Our pip value calculator gives it for any pair.
Two rules turn the result into a real order:
- Round down to your broker’s lot step (usually 0.01). Rounding up means you risk more than planned.
- Place the stop where the trade idea is wrong, then size the lot to fit it. Never shrink the stop to fit a lot you wanted.
Step by step with four examples
All examples use a $10,000 USD account risking 1% ($100). Prices are illustrative.
Example 1: EURUSD, 20-pip stop
- Risk: $100
- Stop: 20 pips
- Pip value: $10 per lot
- Lot size = 100 ÷ (20 × 10) = 0.50 lot
Example 2: GBPUSD, 40-pip stop
- Stop: 40 pips, pip value $10 per lot
- Lot size = 100 ÷ (40 × 10) = 0.25 lot
A wider stop means a smaller lot for the same dollar risk. This is the part new traders skip.
Example 3: USDJPY, 25-pip stop
Here the quote currency is yen, so the pip value is not $10. One pip (0.01) on 100,000 units is 1,000 JPY. At a price of 150.00 that is about $6.67.
- Pip value: 1,000 ÷ 150 ≈ $6.67 per lot
- Lot size = 100 ÷ (25 × 6.67) = 0.60 lot
The pip value moves with the USDJPY price, so recheck it when price changes a lot.
Example 4: Gold (XAUUSD), $5 stop
Gold is quoted in dollars per ounce, and one standard lot is usually 100 oz. A $1 move is about $100 per lot.
- Stop: $5 price distance
- Lot size = 100 ÷ (5 × 100) = 0.20 lot
Brokers describe gold “pips” differently, so for gold it is safer to work in dollars of price movement. Our gold lot size calculator does exactly this.
Lot size by risk percentage
Same $10,000 account, EURUSD, 20-pip stop:
| Risk per trade | Dollars at risk | Lot size |
|---|---|---|
| 0.5% | $50 | 0.25 |
| 1% | $100 | 0.50 |
| 2% | $200 | 1.00 |
Doubling the risk doubles the lot, and it also changes how fast a losing streak hurts. Ten losses in a row at 2% leaves you down about 18%, and you then need about 22% to get back to even. Our drawdown recovery calculator shows the exact numbers for your case, and the risk of ruin calculator shows how risk per trade changes the odds of a bad run.
What risk percentage should you use?
There is no universal number, and nobody can promise one keeps you safe. Many traders working with small edges keep risk at or below 1% per trade so that a long losing streak is survivable. Prop firm traders often go lower, because daily loss and max loss limits are tight. Our The5ers position size calculator checks a lot size against those limits.
Pick a number you can lose ten times in a row without changing your plan.
Check margin after you size
Lot size from risk tells you how much you lose if the stop is hit. It does not tell you whether the account can carry the position. Before sending the order, check the required margin with a margin calculator. If you plan several trades at once, add up their risk too. Risk is spread across all open positions, not just the newest one.
Also check that the trade is worth taking. A 1:1 trade needs to win more than half the time to pay, while a 1:2 trade breaks even near 33%. The risk reward calculator shows this before you enter.
Six mistakes that break the formula
- Using the same lot every trade. A fixed 0.10 lot risks a different amount on every stop distance.
- Rounding up. 0.37 lot rounded to 0.40 is about 8% more risk than planned.
- Ignoring the spread. Your stop is hit at the bid or ask side. On tight stops, spread is a real share of the risk.
- Wrong pip value on JPY pairs and gold. Use the symbol’s actual contract specification.
- Sizing after the stop has moved. Recalculate when you change the stop or add to a position.
- Counting only one trade. Three correlated trades at 1% each behave like one 3% bet.
Calculate it faster on the chart
Doing this by hand once is useful. Doing it on every trade, under pressure, is where mistakes slip in. Our own Lot Architect indicator for MetaTrader lets you drag the entry, stop loss and take profit lines on the chart and shows the lot size, margin, risk and R:R as you move them. Sizing can use risk percent, risk in dollars or fixed lots. It does not give signals and does not guarantee results; it only removes manual math.
These are our own products, and we earn money if you buy them.
Frequently asked questions
How do I calculate lot size for a $100 account?
The formula is the same. At 1% risk you risk $1, so with a 20-pip stop on EURUSD the lot is 1 ÷ (20 × 10) = 0.005, which is below the 0.01 minimum on most brokers. That is the real lesson: very small accounts often cannot size correctly at 1%, and the minimum lot forces higher risk. Use a cent account or a wider-risk plan knowingly, not by accident.
What is the lot size for 1% risk?
It depends on your stop distance and pair, not on the account alone. Use: lot = (balance × 0.01) ÷ (stop in pips × pip value per lot).
Is a bigger lot size better?
No. A bigger lot increases profit and loss at the same rate. It only helps if your risk per trade stays inside your plan.
Does leverage change the lot size?
Not the risk-based lot size. Leverage changes the margin needed to hold the position, not how much you lose when the stop is hit.
Should I change lot size after wins and losses?
Many traders recalculate from the current balance so that risk stays at the same percentage. Others keep it fixed for a set period. Either is fine if you follow it consistently and write it down.
Key takeaways
- Lot size = risk amount ÷ (stop in pips × pip value per lot).
- Set the stop first, then size the lot. Round down.
- Recheck pip value on JPY pairs and gold, and check margin and total open risk.
- Use a calculator or tool so the math is not done under pressure.
Trading leveraged products carries a high risk of loss. This article is educational, not financial advice. Read our risk disclaimer and see how our tools are built.