How to use the position size calculator
- Choose the instrument: shares, futures or options.
- Enter your account size and the share of it you are willing to lose on one trade.
- Enter the entry price and the stop loss. For options, enter the premium you pay and the premium at which you will exit.
- For futures and options, enter the lot size.
The result shows the risk budget, the position size, the loss if the stop is hit and the value of the position, then the size at 0.5%, 1%, 1.5% and 2% risk.
Position size formula
For shares: a ₹5,00,000 account risking 1% has a budget of ₹5,000. Buying at ₹1,385 with a stop at ₹1,360 risks ₹25 a share, so the position is 5,000 ÷ 25 = 200 shares, worth ₹2,77,000. If the stop is hit, the loss is ₹5,000.
| Shares | Nifty futures | Nifty option bought | |
|---|---|---|---|
| Entry and stop | ₹1,385 and ₹1,360 | 25,050 and 24,990 | ₹120 and ₹90 premium |
| Risk a unit | ₹25 | 60 points | ₹30 |
| Risk a lot | Not applicable | ₹3,900 | ₹1,950 |
| Position size | 200 shares | 1 lot | 2 lots |
| Loss if the stop is hit | ₹5,000 | ₹3,900 | ₹3,900 |
| Position value | ₹2,77,000 | ₹16,28,250 | ₹15,600 of premium |
All three use a ₹5,00,000 account and 1% risk. In the futures and options cases the loss at the stop is below the budget, because the size is rounded down to whole lots.
Position sizing calculator for futures
Futures come in whole lots, so the size jumps in steps. One lot of Nifty futures with a 60-point stop risks ₹3,900. The table, from the position sizing calculator above, shows what that means at different risk levels.
| Risk per trade | Budget | Size | Loss if stopped |
|---|---|---|---|
| 0.5% | ₹2,500 | 0 lots | ₹0 |
| 1% | ₹5,000 | 1 lot | ₹3,900 |
| 1.5% | ₹7,500 | 1 lot | ₹3,900 |
| 2% | ₹10,000 | 2 lots | ₹7,800 |
At 0.5% the budget cannot pay for one lot, so the right size is zero: either widen the budget, tighten the stop or skip the trade. A wider stop needs a larger account for the same lot. The position value, ₹16,28,250 here, is more than three times the account, which is why the stop decides the risk and not the margin.
Position sizing in option trading
Position sizing in option trading has two cases.
- Bought options. Size on the premium. With entry ₹120 and exit ₹90, the risk is ₹30 a unit, or ₹1,950 a lot, so a ₹5,000 budget allows 2 lots. Remember the worst case: if the market gaps past your exit, the option can lose more than planned, up to the full ₹15,600 of premium, or 3.1% of the account. Some traders size bought options on the whole premium for that reason.
- Sold options. The loss on a sold option has no cap, and the premium can rise several times in a fast move. Size by the stop you will use, test it against a gap of a few percent in the index, and check the margin; the F&O margin calculator shows it. Hedged positions such as spreads have a known maximum loss, which makes sizing simpler.
Delta does not replace a stop. An option with a delta of 0.5 moves about half as much as the index at first, but the delta changes as the price moves, so size on the premium you will exit at.
Slippage, charges and gaps
A stop loss order limits the loss only if it fills near its price. In a fast market it can fill several points worse. Add the slippage you expect to the stop distance before sizing. A 60-point Nifty futures stop with 10 points of slippage is a 70-point risk, ₹4,550 a lot, still within a ₹5,000 budget.
Charges add to every loss too. A round trip in one lot of Nifty futures costs about ₹968 in brokerage and taxes, as the brokerage calculator shows, so the full loss at a 60-point stop is about ₹4,868. Overnight positions also face gaps: a stock or index can open beyond your stop, and the stop then fills at the open price.
How much to risk per trade
Most rule-based traders risk between 0.5% and 2% of the account per trade. The table shows what is left after a run of losses, with each trade risking the same share of the account as it then stands.
| Risk per trade | After 10 losses in a row | After 20 losses in a row |
|---|---|---|
| 1% | 90.44% of the account | 81.79% |
| 2% | 81.71% | 66.76% |
| 5% | 59.87% | 35.85% |
Runs of ten losses are common for strategies that win less than half the time. At 1% risk the account survives them comfortably; at 5% it loses 40%. Formulas that set the size from the win rate and the payoff, such as Kelly criterion position sizing, often give larger sizes than this and are usually used at a fraction. Pair the size with the trade's target: the risk reward ratio calculator shows the win rate a plan needs to break even.
Related calculators
- Risk reward ratio calculator for the reward against the risk and the break-even win rate
- F&O margin calculator for the margin the position needs
- Stock profit calculator for the result of a share trade after charges and tax
- Option profit calculator for the payoff of an options position
- Kelly criterion position sizing for sizing from the win rate and the payoff
- Lot size meaning for how lot sizes are set
- Options risk management for limits for whole positions and the account
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Frequently asked questions
How do I calculate position size?
Multiply your account by the share you will risk to get the risk budget, then divide it by the distance from entry to stop loss. For futures and options, divide the units by the lot size and round down.
How much should I risk per trade?
Most rule-based traders risk 0.5% to 2% of the account. At 1%, ten losses in a row leave about 90% of the account.
How do I size an options trade?
For a bought option, use the premium you pay and the premium at which you will exit as the entry and the stop. For a sold option, size by your stop, test a gap in the index, and check the margin.
Why does the calculator round down to whole lots?
Rounding up would take the loss above your budget. If one lot already risks more than the budget, the size is zero.
Does position sizing guarantee my maximum loss?
No. A stop can fill worse than its price in a fast market or after a gap, and charges add to the loss. Allow for slippage when you set the stop distance.
Should I size by margin or by risk?
By risk. Margin is what the broker blocks to hold the position. The loss you can take is set by the stop and the size, and one lot of Nifty futures controls a position worth more than ₹16 lakh.
What is the difference between position size and leverage?
Position size is the number of shares or lots. Leverage is the position's value divided by your capital. A 1-lot Nifty futures trade in a ₹5,00,000 account has leverage of about 3.3 times, even though it risks only ₹3,900 at the stop.
Sources
- NSE: revision in market lot of index derivative contracts from the January 2026 series (Nifty 65, Bank Nifty 30)
- Brokerage and statutory charges as in the QuantPower brokerage calculator, rates from 1 April 2026