Position size calculator for options
Most big losses do not come from a bad entry. They come from too many lots on a normal trade. Decide how much of your capital one trade may lose, enter your stop loss and lot size, and see how many lots keep that loss inside your rule.
Your trade
Nothing you enter leaves this page.
The money in your trading account, not your total savings.
The share of capital you accept losing if this trade hits its stop. Many traders keep it at 1% or 2%.
How far the option premium can move against you before you exit. Set it from the chart, before you size the trade.
Units in one lot. Nifty moved to 65 in January 2026. NSE reviews lot sizes from time to time, so check the number in your broker's option chain.
The price you plan to buy at. Used to check the lots fit your capital.
Your position size
2 lots
130 units
- Most you can lose
- ₹3,000
- Risk on one lot
- ₹1,300
- Loss if stop is hit
- ₹2,600
- Premium needed
- ₹15,600
If the stop is hit, you lose ₹2,600. That is inside your 1% rule. One more lot would take the loss to ₹3,900, past your limit.
This calculator runs in your browser. Nothing you enter is sent to us, stored or logged. It is built for buying options. Selling options needs margin and is not covered here.
Why position size matters more than the entry
Two traders can take the same trade, with the same entry and the same stop. If one takes 2 lots and the other takes 10, the second one loses five times as much on the same mistake. The chart was the same. The size was not.
Sizing from a fixed risk per trade keeps any single loss small enough to recover from. Ten losing trades in a row at 1% risk cost about a tenth of your capital. At 5% risk, the same streak costs about 40%.
The hard part is not the maths. It is keeping to the number after a loss, when the urge is to double up and win it back. Our guide to stopping revenge trading covers what to do in that moment.
Questions
How do I calculate position size for options?
Multiply your capital by the share you will risk, for example 1% of ₹3,00,000 is ₹3,000. Multiply your stop loss in points by the lot size to get the risk on one lot. Divide the first number by the second and round down. That is your number of lots.
How much should I risk per trade?
Many traders keep it at 1% or 2% of capital. The exact number matters less than keeping it the same on every trade, especially the one right after a loss.
What if even one lot risks too much?
Then the trade does not fit your account at that stop. Use a tighter stop that still makes sense on the chart, pick a cheaper contract, or skip the trade. Do not widen your risk rule to make it fit.
Does this work for option selling?
No. It is built for buying options, where the premium you pay is the most you can lose on the position. Selling needs margin and can lose more than the premium you collect.
Does this calculator send my numbers anywhere?
No. It is arithmetic that runs in your browser. Nothing you enter is sent, stored or logged.
Size every trade. Then cap the day.
Position size limits one trade. A daily loss limit protects the whole day. LossGuardian watches your real P&L from your broker and alerts you the moment you reach the limit you set. It is read-only, so it never places or cancels an order.