Position Size Calculator
Most beginners decide how many shares to buy by feel: a round number, whatever the balance allows, or the same quantity as last time. Position sizing turns that decision around. You first decide how much of your capital you are prepared to lose if the trade plan is wrong, and only then work out the quantity.
The logic is short. Your risk amount is a fixed percentage of your capital, often a small one such as 0.5% or 1%. The gap between your entry and your stop-loss is the risk on each share. Divide the first by the second and you have a quantity that keeps a loss at the stop-loss within your limit, however wide or tight the stop is.
This calculator does that arithmetic for you. Enter your account capital, the percentage you are willing to risk on one trade, your planned entry and stop-loss, and, for futures and options, the contract lot size. It shows the amount at risk, the quantity (rounded down to whole shares or whole lots), and the total position value, so you can also see how much capital the position would tie up.
It is a learning tool for understanding risk. It does not suggest what to trade or where to place a stop-loss.
How to use this calculator
1. Enter your account capital in rupees.
2. Enter the percentage of capital you are prepared to risk on this one trade, for example 1.
3. Enter your planned entry price and your stop-loss price. A stop-loss below entry is read as a long position; above entry, as a short position.
4. If you trade futures or options, enter the lot size. The quantity is then rounded down to whole lots. Leave it blank for shares.
5. Tap Calculate. Check the amount at risk, the quantity and the position value, and read the note if the position is larger than your capital.
Worked example
Capital ₹5,00,000. Risk per trade 1%. Entry 1,250. Stop-loss 1,230.
• Amount at risk = 5,00,000 × 1% = 5,000
Risk per share = 1,250 − 1,230 = ₹20
• Quantity = 5,000 ÷ 20 = 250 shares
• Position value = 250 × 1,250 = 3,12,500 (62.5% of capital)
With a lot size of 75, the 250 shares round down to 3 lots: 3 × 75 = 225 units. Position value = 225 × 1,250 = 2,81,250, and the actual loss at the stop-loss = 225 × 20 = 4,500, which is inside the ₹5,000 limit.
Frequently asked questions
What does position size mean?
Position size is the quantity of shares or contracts in one trade. Here it is worked out from the amount you are prepared to lose if the price reaches your stop-loss, rather than from how much money is available.
Why is the quantity rounded down?
Rounding down keeps the loss at your stop-loss at or below the amount you chose. Rounding up would let a single trade risk slightly more than your limit.
Does the calculator include brokerage, taxes or slippage?
No. It uses the prices you enter. Brokerage, taxes, slippage and price gaps past the stop-loss can make a real loss larger than the figure shown.
Is this investment advice?
No. It is an educational calculator. It does not suggest any security, entry, stop-loss or risk level. Those decisions stay with you.
Education only. These are educational calculators, not investment advice.
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