Position size calculator: shares from a risk budget
Turn a risk budget into a number of shares: capital, the percentage you would lose if the stop is hit, and a stop set a multiple of ATR (average true range) away. The 1% and 2× ATR are conventions, not recommendations.
Prefilled with: Britannia on 1 January 2026, the calmest day in the position sizing post's window (historical, for illustration).
What it does
Position sizing starts from the rupees you are prepared to lose, not the rupees you hope to make. Enter your capital, the percentage of it you’d lose if the stop is hit, the share price, its ATR (average true range) and how many ATRs away the stop sits. The calculator shows the rupees at risk, the stop price, the number of shares and how big the position is relative to your capital.
It starts from the post’s calmest day for one stock, a historical example. Reset to the post’s example puts it back.
The formula
Risk (₹) = Capital × risk %
Stop distance = k × ATR
Shares = Risk ÷ Stop distance (rounded down)
What it leaves out
The 1% risk and the 2× ATR stop are conventions from the trading literature, not recommended settings. The calculator doesn’t pick a stock, a price or a stop for you. It assumes the stop fills at its price: a gap through it, or a fast market, loses more than the budget. Brokerage, taxes and slippage aren’t modelled, and a stop-based method doesn’t map neatly onto long-term investing in funds, where there’s no stop price.
How it works
The method, step by step, with the worked example this tool reproduces: Position sizing: the 1% rule, and letting volatility pick the number.