Position size calculator
Work out the right lot size for Gold (XAUUSD), Bitcoin, Ethereum, US100, US500, US30, US Oil and Natural Gas, from your account size, risk and stop loss, with spread, commission and margin included. Free, no sign-up.
How the lot size is calculated
Lots = Money at risk ÷ ((Stop distance + Spread) × Contract size + Commission per lot)
Decide how much money you are willing to lose before you pick a lot size. The stop distance then sets the size: a tight stop allows more lots, a wide stop needs fewer, and every losing trade costs about the same. The money a price move is worth depends on the contract size: 1 lot of gold is usually 100 ounces, so a $1.00 move is worth $100 per lot. The result is rounded down to your broker's lot step so the risk is never exceeded.
Typical contract sizes
| Market | Also called | 1 lot | A 1.00 move, per lot |
|---|---|---|---|
| Gold | XAUUSD, GOLD | 100 oz | $100 |
| Bitcoin | BTCUSD | 1 BTC | $1 |
| Ethereum | ETHUSD | 1 ETH | $1 |
| US Tech 100 | US100, NAS100, USTEC | $1 × index | $1 per point |
| US 500 | US500, SPX500 | $1 × index | $1 per point |
| US 30 | US30, DJ30, WS30 | $1 × index | $1 per point |
| US Oil (WTI) | USOIL, WTI, XTIUSD | 1,000 barrels | $1,000 |
| Natural Gas | NATGAS, XNGUSD | 10,000 MMBtu | $10,000 |
Brokers differ (some indices are $10 or $20 per point, some oil contracts are 100 barrels). Check yours in your trading platform: open the symbol's contract specification and read the contract size.
Worked examples
| Market | Risk | Stop + spread | Per lot | Lot size |
|---|---|---|---|---|
| Gold XAUUSD | $100 | $15.00 + $0.20 | 15.20 × 100 = $1,520 | 100 ÷ 1,520 = 0.06 lots |
| US100 | $100 | 70 + 1.5 points | 71.5 × $1 = $71.50 | 100 ÷ 71.5 = 1.39 lots |
| US Oil | $100 | $0.50 + $0.03 | 0.53 × 1,000 = $530 | 100 ÷ 530 = 0.18 lots |
Practise the sizes risk-free in the paper trading simulator, with the same markets. Read the full guide: how to calculate position size.
Go further in the free workspace
The Ten12 Mentors workspace adds a pre-trade checklist and, for Pro members, checks every trade against your daily loss limit, losing streak and total open risk. Ten12 GuardX can help you keep to your risk rules.
Frequently asked questions
How do I calculate the lot size for XAUUSD (gold)?
On most platforms 1 lot of XAUUSD is 100 ounces, so a $1.00 move is $100 per lot. Divide the money you are willing to lose by (stop distance + spread) × 100. Example: $100 risk with a $15 stop and a $0.20 spread gives 100 ÷ 1,520 = 0.06 lots.
How is the lot size worked out for US100, US500 and US30?
Index contracts are usually $1 per point for 1 lot, so lots = money at risk ÷ (stop in points + spread). Some providers use $10 or $20 per point: change the contract size to match yours.
What contract size should I use for US Oil and Natural Gas?
Common settings are 1,000 barrels per lot for US Oil (WTI) and 10,000 MMBtu per lot for Natural Gas. Providers differ, so check the contract specification on your platform and enter that contract size.
Does the calculator include spread and commission?
Yes. The spread is added to the stop distance and the commission per lot (round trip) is added to the cost of a full stop, so a stopped-out trade costs no more than your planned risk.
How much should I risk per trade?
Many educators suggest 0.5% to 1% of the account per trade while learning, and rarely more than 2%. Prop-firm style rules, like those in the Ten12 Challenge, often cap risk at 2% per trade.
Educational calculator. Contract sizes, spreads and commissions differ by broker; results are estimates and not a recommendation to trade. Trading carries a substantial risk of loss.