On this page (11 questions)
- ↑ Calculator
- 1What does a position size calculator (lot size calculator) do?
- 2How do you calculate lot size?
- 3How much is a 0.01 lot worth?
- 4Why is pip value different for JPY pairs and cross pairs?
- 5How do you calculate lot size for gold (XAUUSD)?
- 6How do you calculate lot size for US30 and NAS100?
- 7How do you size futures contracts like MNQ?
- 8What lot size fits a $500, $5,000 or $10,000 account?
- 9How much should you risk per trade?
- 10How does a prop firm's daily loss limit affect position size?
- 11Why does the calculator round down?
What does a position size calculator (lot size calculator) do?
It works out how big a trade can be so that, if your stop-loss is hit, you lose only the amount you chose to risk. A lot size calculator answers the same question: forex and CFD positions are measured in lots, futures in contracts.
Position sizing always comes back to one idea: risk amount ÷ what one unit of the position loses if the stop is hit. What changes between markets is how “one unit” is measured, whether that’s a pip on a forex lot, a dollar on an ounce of gold, a point on an index CFD or a tick on a futures contract.
How do you calculate lot size?
Lots = risk amount ÷ (stop-loss in pips × pip value per lot), where the risk amount is your account balance × your risk percentage. With a $10,000 account, 1% risk and a 20-pip stop on EUR/USD, that’s $100 ÷ (20 × $10) = 0.50 lots.
The $10 comes from the size of a standard lot. A standard lot is 100,000 units of the base currency, and on a pair like EUR/USD each pip is worth $10. Smaller lots scale down in proportion:
Lot sizes
| Lot | Size in the platform | Units of base currency | Pip value on a USD-quoted pair |
|---|---|---|---|
| Standard | 1.00 | 100,000 | $10.00 |
| Mini | 0.10 | 10,000 | $1.00 |
| Micro | 0.01 | 1,000 | $0.10 |
Worked example
- Risk amount$10,000 × 1%= $100
- Loss per lot if the stop is hit20 pips × $10= $200
- Position size$100 ÷ $200= 0.50 lots
How much is a 0.01 lot worth?
A 0.01 lot is 1,000 units of the base currency, so on a pair quoted in US dollars, such as EUR/USD, one pip is worth $0.10. On JPY pairs and on pairs where the dollar is the base currency, the pip value moves with the exchange rate.
That’s why a fixed “$10 per pip” rule only works for pairs quoted in your account currency. For every other pair, the calculator works the pip value out from the exchange rate.
Why is pip value different for JPY pairs and cross pairs?
On JPY pairs a pip is 0.01 instead of 0.0001, because the yen is quoted to two decimal places. And when your account currency isn’t the pair’s quote currency, the pip value has to be converted: at your stop price if your account currency is in the pair (USD/JPY in a USD account), or at the current exchange rate if it isn’t (EUR/GBP in a USD account).
For USD/JPY, one pip is 0.01 yen per dollar, where EUR/USD uses 0.0001. So one pip on a standard lot is 100,000 × 0.01 = 1,000 yen. For a USD account with USD/JPY at 150.00, that’s 1,000 ÷ 150 = $6.67 per pip, not $10. Size a JPY trade with the $10 figure and you’ll risk about a third less than you meant to.
Cross pairs such as EUR/GBP work the same way: the pip value is in the quote currency (GBP) and gets converted to your account currency.
How do you calculate lot size for gold (XAUUSD)?
At many brokers one lot of XAUUSD is 100 troy ounces, so a $1 move in gold changes a 1-lot position by about $100. Divide your risk by (stop distance in dollars × 100) to get lots, after checking your broker’s contract size.
That 100-ounce figure is common but not universal. A standard lot “commonly represents 100 ounces in retail CFD trading”, and brokers can use a different contract size, so look up the symbol’s specification in your platform before you trust any gold calculation, including this one.
Example: $10,000 account, 1% risk ($100), stop $5.00 below entry. Loss per lot is $5 × 100 oz = $500, so the position is $100 ÷ $500 = 0.20 lots.
How do you calculate lot size for US30 and NAS100?
Index CFDs are sized by the value of one point per lot, and that value differs between brokers. Find it in your broker’s contract specification, then lots = risk ÷ (stop in points × value per point per lot).
Example, assuming a contract worth $1 per point per lot (check yours): $100 risk and a 50-point stop on US30 give $100 ÷ (50 × $1) = 2.00 lots. If your broker’s contract is $10 per point, the same trade is 0.20 lots. That factor of ten is why the calculator asks for the value per point rather than guessing it.
How do you size futures contracts like MNQ?
Futures are sized in whole contracts: contracts = risk ÷ (stop in ticks × tick value), rounded down. The Micro E-mini Nasdaq-100 (MNQ) is $2 × the Nasdaq-100 index with a minimum tick of 0.25 index points, so one tick is worth $0.50 per contract.
Example: $200 risk, 20-point stop on MNQ.
Worked example
- Stop in ticks20 points ÷ 0.25= 80 ticks
- Loss per contract80 × $0.50= $40
- Contracts$200 ÷ $40= 5 contracts
For any other contract, enter its tick size and tick value from the exchange’s specification and the calculation is the same.
What lot size fits a $500, $5,000 or $10,000 account?
The balance alone doesn’t decide it. The size also depends on your risk percentage and stop distance, so the same account can take a small position on a wide stop or a larger one on a tight stop.
Choose a risk percentage first, then let the stop set the size. At 1% risk and a 20-pip stop on EUR/USD ($10 per pip per lot):
- $500 account:$5 ÷ $200 = 0.025 lots, which rounds down to 0.02 lots
- $5,000 account:$50 ÷ $200 = 0.25 lots
- $10,000 account:$100 ÷ $200 = 0.50 lots
Double the stop to 40 pips and every one of those sizes halves before rounding, giving 0.01, 0.12 and 0.25 lots.
How much should you risk per trade?
That’s your decision, and this calculator won’t make it for you. It shows what each choice means in money: on $10,000, 0.5% is $50, 1% is $100 and 2% is $200.
It helps to see a losing streak in numbers. Ten losses in a row, each risking a fixed percentage of the current balance, leave you down about 4.9% at 0.5%, 9.6% at 1% and 18.3% at 2%.
How does a prop firm's daily loss limit affect position size?
A daily loss limit caps what you can lose in one day, so size each trade so that the losses you might take today still fit under it. If the limit leaves $500 of room and you might take three losing trades, each trade should risk no more than about $166.
Work out that room from your firm’s own rules, including whether it counts open trades and how it resets. Firms define it differently, and the calculator only knows the numbers you give it.
Why does the calculator round down?
Brokers accept position sizes only in fixed steps, and futures trade in whole contracts, so the exact answer usually has to be rounded. Rounding down keeps your real risk at or below what you chose; rounding up would put you over it.
The result also doesn’t include spread, commission, swap or slippage, which can make a real loss slightly bigger than the planned risk. This calculator is a tool for doing the arithmetic, not trading advice.