Position sizing is the whole game

Ask a struggling trader what they are working on and you will almost always hear about entries. A better indicator, a cleaner setup, the right pattern.

Almost nobody says "my position sizing." Which is unfortunate, because that is where the account is actually being lost.

The arithmetic nobody wants to do#

Losses and the gains needed to recover them are not symmetric. This is not a motivational point; it is arithmetic:

At 50% you need to double your money just to get back to flat — with half the capital, and a damaged decision-making process.

There is a level of drawdown beyond which recovery stops being a trading problem and becomes a fantasy. Position sizing is what keeps you on the survivable side of that table.

Why F&O makes this urgent#

In the cash market, sizing errors are slow. Buy too much of a stock and you have an uncomfortable position, but the stock does not usually halve overnight.

Derivatives compress that timeline. Lot sizes mean the minimum position is often larger than a small account should carry. Leverage means a modest adverse move is a large rupee loss. Expiry means there is no waiting it out.

There is also a structural issue that is not discussed enough: when regulators raise contract values, the minimum viable account size rises with them. After a lot-size increase, a single lot can represent more risk than a ₹50,000 account should ever take on one trade. The trader has not changed. The minimum bet has.

If that describes you, the honest answer is not to take the trade anyway with a tighter stop. It is that this instrument is currently too large for this account.

The rule#

Risk a small, fixed percentage of capital on any single trade. Most durable traders use somewhere between 0.5% and 2%.

Note carefully what that percentage refers to. It is not how much capital you deploy. It is how much you lose if the trade goes to your stop.

Risk budget   = capital × risk %
Risk per lot  = |entry − stop| × lot size
Lots          = floor(risk budget ÷ risk per lot)

That floor matters. Round down, always. Rounding 1.8 lots up to 2 quietly converts your 1% rule into a 1.4% rule, and it will be the trade you round up on that hurts.

Work out a real number#

Try these three cases:

1. ₹2,00,000 capital, 1% risk, entry ₹180, stop ₹120, lot 75. Risk per lot is ₹4,500 against a ₹2,000 budget — the calculator returns zero lots. Not a bug. The trade does not fit the account.
2. Now widen the stop to ₹90. Risk per lot gets worse, not better. A wider stop on the same capital is not a fix.
3. Now set capital to ₹10,00,000. The same trade becomes two lots and fits comfortably. Nothing about the trade changed — only whether this account could carry it.

The three ways people break the rule#

Averaging down. A losing position gets added to, so the risk you accepted at entry doubles. The original plan said you were wrong at the stop. Adding says you were right, just early — a claim with no evidence behind it.

Revenge sizing. After a loss, the next trade is bigger to recover it. This is the mechanism that turns a 5% drawdown into a 40% one, and it happens in the moment when your judgement is at its worst.

Drift. No single decision, just gradually larger positions after a good run. Sizing quietly doubles over a month, and the first serious loss now costs several times what an equivalent loss cost you earlier.

All three feel like different mistakes. They are the same one: the size stopped being decided in advance.

Why this beats a better strategy#

Two traders, same 55%-win-rate system, same 1:1 payoff.

Trader A risks 1% per trade. A run of six losses — which will happen, and often — costs about 6%. Annoying, entirely recoverable, and the system carries on working.

Trader B risks 10% per trade because the edge looks good. The same six-loss run costs roughly 47%. Now they need close to a double just to get back to flat, and they will almost certainly change the system before that happens — abandoning an edge that was working, because the sizing made a normal losing streak feel like proof of failure.

Same strategy. Same market. Same trades. Completely different outcomes, decided entirely by a number chosen before either trade was taken.