Options Position Sizing: How Much to Risk Per Trade
Decide the rupees you are willing to lose on a trade before you decide how many lots to buy. That order of operations is what position sizing means, and for most retail option traders the number sits between 1% and 2% of trading capital per trade.
Position sizing is the calculation that converts a fixed rupee risk budget into a lot count, using the distance between your entry and your planned exit as the risk per lot. Get it right and a bad run is survivable. Get it wrong and one week can undo a year.
What follows is the arithmetic: setting the budget, why margin is not risk, a worked example on a Rs 5 lakh account, and the errors that show up in real accounts.
Start with one number: rupees at risk per trade
Pick a percentage of your trading capital you accept losing on any single idea. Not your net worth, not your salary. The capital allocated to options.
One percent is conservative and slow. Two percent is common among traders with a tested method. Above three percent you need a hit rate most people do not have. On a Rs 4,00,000 account, 2% is Rs 8,000, and that is your ceiling for the trade including charges. The budget is a cap that lets you be wrong repeatedly without being removed from the game.
Is the margin your broker asks for the same as your risk?
No, and confusing the two is the most expensive mistake in this topic.
Margin is a deposit the clearing corporation requires to cover adverse movement. Risk is what you actually lose if the trade fails. For a bought option they coincide, since maximum loss is the premium. For a sold option, SPAN and exposure margin might be Rs 1,20,000 while the possible loss is far larger, because a short naked option has no upper bound.
So the sequence is never “I have margin for four lots, so I will take four”. It is “my risk budget allows this loss, therefore this many lots”. What gets blocked is explained here on options margin requirements.
The sizing formula, step by step
- Fix your options capital figure and write it down.
- Multiply by your risk percentage for the rupee budget.
- Define the exit before entry: the premium at which you cut, or the level that invalidates the idea.
- Compute risk per unit: entry premium minus exit premium for a buyer, exit minus entry for a seller.
- Multiply risk per unit by lot size for risk per lot, then divide the budget by that figure and round down. Always down.
- Check margin last, taking the smaller of what risk allows and what margin allows.
If the formula returns less than one lot, the trade is too big for the account. That is information, not an obstacle to work around.
A worked example on a Rs 5 lakh account
Buying a call
Capital is Rs 5,00,000 and your risk setting is 1.5%, so the budget is Rs 7,500. Nifty is at 25,000 and the 25,000 call trades at Rs 120. Suppose the lot size is 75, so one lot costs 120 multiplied by 75, which is Rs 9,000.
You plan to exit if the premium halves, at Rs 60. Risk per unit is Rs 60, so risk per lot is 60 multiplied by 75, which is Rs 4,500. Then 7,500 divided by 4,500 is 1.67. Round down: one lot.
Change one thing. If you hold to expiry with no stop, risk per lot is the full Rs 9,000 premium, so 7,500 divided by 9,000 is 0.83, meaning zero lots. The trade does not fit unless you accept a stop or pick a cheaper strike, say a further out of the money call at Rs 45, where one lot risks Rs 3,375.
Selling a strangle
Same account. You sell one lot each of a call and a put, collecting Rs 150 per unit combined, so Rs 11,250. Margin might be around Rs 1,50,000.
Your rule is to close if the combined premium doubles to Rs 300. Risk per unit is Rs 150, so risk per lot pair is Rs 11,250, which is 2.25% of capital. That exceeds a 1.5% budget, so the position is one size too large. Tighten the stop to Rs 250 and risk becomes 100 multiplied by 75, so Rs 7,500 and exactly 1.5%.
Notice what never entered the calculation: the Rs 1,50,000 margin. The account could fund three such positions; risk sizing says not even one at the original stop. This walkthrough on calculating options profit and loss covers the payoff side.
Risk note: a stop on a short option is a plan, not a guarantee. On a gap opening the premium can be past your level before you act, so the loss can exceed the sized amount, a hazard described here on naked options.
How many lots can you trade with Rs 1 lakh?
Often one, sometimes none. The table assumes a Rs 120 premium, a lot size of 75, and an exit at half the premium, so Rs 4,500 risk per lot.
| Options capital | Risk at 1% | Risk at 2% | Lots at 1% | Lots at 2% |
|---|---|---|---|---|
| Rs 1,00,000 | Rs 1,000 | Rs 2,000 | 0 | 0 |
| Rs 2,50,000 | Rs 2,500 | Rs 5,000 | 0 | 1 |
| Rs 5,00,000 | Rs 5,000 | Rs 10,000 | 1 | 2 |
| Rs 10,00,000 | Rs 10,000 | Rs 20,000 | 2 | 4 |
Zero lots on a Rs 1,00,000 account is not a failure of the method. It says one index lot is too large a bite, so the routes are a cheaper strike, a debit spread, or building capital first. Lot sizes are revised periodically by the exchanges, so confirm the current one on the NSE contract specifications page.
Why a run of losses matters most
Losses compound against you. Five straight losses at 2% risk leave 0.98 to the power of five, about 0.904, so roughly a 10% drawdown. Recoverable. Five at 10% risk leave 0.90 to the power of five, about 0.590, a 41% drawdown needing a 69% gain to get back to even. Streaks of five losers are ordinary at a 55% hit rate.
Sizing mistakes that end accounts
- Doubling size after a loss to win it back, which turns a normal drawdown into a terminal one.
- Stacking correlated positions. Three Nifty trades in the same direction is one position at triple size.
- Ignoring charges. STT at 0.15% on premium sold, plus brokerage and GST, widens the real loss beyond the modelled one, one of several common options trading mistakes.
Frequently Asked Questions
What percentage of my capital should I risk on one options trade?
Between 1% and 2% suits most retail traders. Use 1% while your method is unproven or your win rate unmeasured, and consider 2% only after several months of recorded results. Above 3%, a normal streak of five or six losses digs a hole deep enough that most people quit the method.
Should position size change when implied volatility is high?
Yes, indirectly. High implied volatility means bigger premiums and wider swings, so the same stop distance in percentage terms costs more rupees per lot. Since risk per lot rises, the formula returns fewer lots on its own. Keep the budget fixed and let the lot count fall.
Can I use a stop loss order on options?
You can, and stop limit orders are usually preferred to market stops, because option books can be thin and a market stop may fill far from your level. A gap opening can also jump past your trigger. Treat stops as a discipline tool, not a promise of an exact exit price.
Does position sizing change for weekly versus monthly options?
The formula stays the same but the inputs change. Weekly options decay fast, so premiums move violently in percentage terms and a normal intraday swing can hit a tight stop. Many traders use a wider stop on weeklies, which raises risk per lot and so reduces the lots the same budget allows.
How does tax treatment affect the capital I should allocate?
F&O income is non speculative business income reported in ITR-3, and losses carry forward for eight years, but only if you file the return by the due date. That relief does not make losses cheap, and it should never widen your per trade risk.
Key Takeaways
- Set the rupee risk first, then derive lots: budget divided by risk per unit multiplied by lot size, rounded down.
- Margin is a deposit requirement, not a measure of risk, and a short option’s loss can far exceed it.
- On a Rs 5,00,000 account at 1.5% risk, a Rs 120 premium with a Rs 60 stop and a 75 unit lot supports one lot, not two.
- If the formula returns less than one lot, take a cheaper strike or a defined risk spread instead.
- Five losses at 2% risk cost about 10% of capital; five at 10% cost about 41%, needing a 69% gain to recover.
