How position size is calculated
Position size answers one question: how much can I buy or sell so that, if my stop is hit, I lose exactly what I planned and not a rupee more?
Lots = Quantity ÷ Lot size, rounded down
Example: you risk ₹2,000 on a Nifty option bought at ₹152.5 with a stop at ₹128. Risk per unit is ₹24.5, so you can hold up to 81 units. Rounded down to whole lots of your contract's size, the actual risk is never above ₹2,000.
Why think in R
R is the amount you risk on a trade. A trade that makes twice its risk is +2R; a full stop-out is −1R. Measuring every trade in R lets you compare a Nifty option with a BTC scalp, and shows whether your winners are big enough to pay for your losers.
Forex lot size calculator
In forex, size is counted in lots: a standard lot is 100,000 units of the base currency, a mini lot 10,000 and a micro lot 1,000. Pick Forex / Gold above and the calculator turns your risk into lots, rounded down to 0.01.
Example: a $5,000 account risking 1% ($50) on EURUSD, entry 1.1650 and stop 1.1680 (30 pips). One standard lot moves $300 over those 30 pips, so the size is 50 ÷ 300 = 0.166 → 0.16 lots (16,000 units), and the actual risk is $48. For pairs that don’t end in your account currency (USDJPY with a dollar account), enter the conversion rate so the risk comes out in dollars.
Gold (XAUUSD) lot size
One lot of gold is usually 100 ounces, so a $1 move is $100 per lot. Set units per lot to 100. Example: risking $50 with entry 3,640 and stop 3,628 ($12) gives 50 ÷ 1,200 = 0.041 → 0.04 lots, risking $48. Some brokers use other contract sizes for gold and indices — use theirs.
Add this calculator to your website
Run a trading blog, a course or a Telegram channel's website? Put this position size calculator on your own page for free. Pick the look, copy the code and paste it into an HTML block. No sign-up, and it works on WordPress, Blogger, Webflow and plain HTML.
Frequently asked questions
How is position size calculated?
Divide the amount you are willing to lose on the trade by the distance between your entry and your stop. The result is the number of units. For F&O, divide units by the lot size and round down to whole lots.
What is R in trading?
R is the amount you risk on a trade. A trade that makes twice its risk is +2R; a full stop-out is −1R. Measuring in R lets you compare trades of any size and in any market.
How much should I risk per trade?
Many traders keep risk to a small, fixed slice of capital, often 0.5% to 2% per trade, so a losing streak cannot wipe out the account. The right number is one you will follow every single time.
Why does the calculator round lots down?
Rounding up would put you above your planned risk. If even one lot is more than your risk, the trade is too big for your rule: skip it or pick a contract with a tighter, valid stop. Don’t move the stop just to fit.
How do I calculate lot size in forex?
Divide your risk by the money one standard lot makes or loses between your entry and stop. With $50 of risk and a 30-pip stop on EURUSD ($300 per standard lot), that is 0.16 lots. The Forex / Gold mode does this for you and rounds down to 0.01 lots.
How do I calculate lot size for gold (XAUUSD)?
A gold lot is usually 100 ounces, so each $1 move is $100 per lot. Divide your risk by (stop distance × 100): $50 of risk with a $12 stop gives 0.04 lots. Check your broker’s contract size.
Does this work for crypto and US stocks?
Yes. Switch to Stocks / Crypto and the result is in units, which can be fractional for crypto. Pick $ for dollar-priced markets.
Track every trade in R, automatically
Profit Prism Journal measures each trade in R, gives every setup its own stats, and warns you before you break your loss limits.
Start journalingFor education only. Not investment advice. Trading involves substantial risk of loss.