Fixed Position Size

Quick answer: Fixed position size is the simplest sizing rule, in which every trade uses the same fixed quantity of lots, contracts or shares regardless of the trade's stop distance, volatility or the account's current equity.

In simple words

Fixed position sizing means you always trade the same amount, for example one lot of Nifty every time, no matter what the setup looks like. It is the easiest rule to follow because there is nothing to calculate. The weakness is that it treats every trade as if it carried the same risk, when a wide stop or a volatile day can make one lot far more dangerous than another. It is a reasonable starting point but a blunt instrument.

Purpose

Fixed position sizing exists as the default, lowest-effort way to size trades; understanding it matters mainly to see why more risk-aware methods replace it.

Visual explanation

Professional explanation

What fixed position sizing actually is

Fixed position sizing commits to a constant trade quantity that does not change from trade to trade: always one lot, always two lots, or always a set number of shares. The size is chosen once, usually from what the account can afford or what feels comfortable, and then repeated. Because nothing is recomputed per trade, it is the least demanding method to operate and the easiest to automate or follow by hand. Its defining feature, constancy, is also the root of its problems, because real trades are not equally risky.

It ignores the risk of the individual trade

The money actually lost on a losing trade is the quantity times the stop distance times the point value, so holding quantity fixed lets the loss vary with the stop distance. A tight ten-point stop and a wide hundred-point stop, both traded at one lot, expose the account to ten times different rupee losses even though the position size is identical. Fixed sizing therefore controls the wrong variable: it fixes the number of lots rather than the amount at risk, which is the number that governs survival. Two trades that look the same on the ticket can carry wildly different threats to capital.

It does not adapt to volatility or account growth

A fixed quantity behaves very differently as conditions change. In a calm market one lot of Bank Nifty risks a modest sum on a normal daily range, but in a volatile regime the same lot can swing several times as much, so a constant size silently raises risk exactly when danger is highest. Fixed sizing also fails to compound: as the account grows, the constant lot becomes a smaller fraction of equity, slowing growth, and as the account shrinks in a drawdown, the same lot becomes a larger fraction, accelerating losses. It is pro-cyclical in the wrong direction.

Where a fixed size is defensible

There are narrow cases where fixed sizing is acceptable. If every trade genuinely uses a similar stop distance in a similar-volatility instrument, then fixing quantity approximately fixes risk, and the method is a passable shortcut. It is also useful as a deliberately conservative cap, one lot maximum, for a beginner learning process before adding complexity, or when exchange lot indivisibility means a small account can only ever trade one lot anyway. In these situations the simplicity is a feature rather than a flaw, provided the trader knows the assumptions being relied on.

Why professionals move beyond it

Serious risk frameworks almost always replace fixed sizing with a risk-based method, because the goal is to hold the rupee risk per trade roughly constant, not the lot count. Fixed fractional and percentage-risk models compute the quantity from the stop distance so that each loss costs a similar fraction of capital, and volatility-based methods further adjust for how much the instrument is moving. Fixed sizing is best understood as the baseline these methods improve upon, the sizing equivalent of a flat rate that ignores the specifics of each case.

Formula

Fixed position size vs fixed fractional sizing

Practical example

Advantages

• Requires no calculation, so it is trivial to follow and automate
• Removes discretion over size, reducing one source of impulsive decisions
• Acceptable when every trade uses a similar stop in a similar instrument
• Serves as a simple conservative cap while a beginner learns process

Limitations

• Fixes the lot count, not the rupee risk, so losses vary with the stop distance
• Ignores volatility, raising real risk in turbulent regimes at the same size
• Does not compound as equity grows nor de-risk as equity falls
• Can indirectly encourage tight, unsound stops just to keep a lot affordable
• Treats a low-conviction and high-conviction trade as identical in size

Common mistakes

• Assuming one lot means constant risk when the stop distance varies
• Keeping the same size after a large drawdown, so it becomes a bigger fraction
• Never increasing size as the account grows, capping compounding
• Trading a fixed lot in a volatile instrument sized for a calm one
• Choosing the fixed size from margin available rather than risk tolerated
• Widening or removing the stop to make a fixed lot fit a bad entry

Professional usage

Professional desks rarely use a purely fixed size except as a hard cap, for instance a maximum lots-per-trade limit layered on top of a risk-based model. The primary sizing logic almost always targets a constant risk per trade rather than a constant quantity, because the rupee at risk, not the lot count, is what compounds a drawdown. When a fixed quantity does appear, it is usually a constraint imposed by lot indivisibility or a per-instrument position limit, not the method by which size is chosen.

Frequently asked questions

Voice search & related questions

Natural-language questions people ask about Fixed Position Size.

Sources & references

Last reviewed 12 July 2026. Educational content only — not investment advice. Markets and rules change; verify current conventions with SEBI, NSE/BSE and your broker.