The 1% rule, and the arithmetic most traders skip

How much you can lose on one trade decides your position size — not conviction. The formula, worked through with real numbers.

· 2 min read

Most people decide how many shares to buy by asking how much they want to make. The 1% rule turns that around: you decide how much you can afford to lose, and the position size falls out of the arithmetic.

The rule

Risk no more than 1% of your account on a single trade. On ₹10,00,000 that is ₹10,000 — not the amount you invest, the amount you lose if the trade goes against you and your stop is hit.

That distinction is where most of the confusion lives. Buying ₹2,00,000 of a stock is not risking ₹2,00,000. You are risking the distance between your entry and your stop.

Working it through

Say you want to buy a stock at ₹1,500 and you have decided that below ₹1,460 your reason for owning it no longer holds.

Step 1 — your risk budget.

₹10,00,000 × 1% = ₹10,000

Step 2 — what one share risks.

₹1,500 − ₹1,460 = ₹40

Step 3 — the position size.

₹10,000 ÷ ₹40 = 250 shares

So you buy 250 shares — ₹3,75,000 of stock — and if the stop is hit you lose ₹10,000. The position looks large. The risk is not.

The part people get wrong

A tighter stop does not mean less risk. It means a bigger position for the same risk, and a greater chance of being stopped out by ordinary noise before the idea has a chance to work.

Move the stop to ₹1,490 in the example above and the arithmetic gives you 1,000 shares — ₹15,00,000 of stock on a ₹10,00,000 account, which you cannot buy without leverage. The rule has not saved you from anything; it has told you the stop is too tight for the size you were imagining.

This is why the calculator caps the suggested quantity at what your capital can actually buy, and reports the real maximum loss rather than the budget you asked for. Because shares come in whole numbers, the two are rarely identical.

Why 1%

There is nothing sacred about the number. It is a survival rate.

At 1% per trade, ten consecutive losses cost about 10% of the account. At 5%, the same streak costs 40%, and recovering from 40% takes a 67% gain rather than an 11% one. The asymmetry is what does the damage: losses compound against you faster than gains compound for you.

Ten losses in a row is not a hypothetical. Any strategy with a 50% hit rate will produce that run eventually, and the only question is whether your account is still there when it does.

Try it before you risk anything

The position size calculator does this arithmetic for any entry and stop, and the paper trading desk lets you run the result with virtual capital — including brokerage and statutory charges, which quietly change the maths on small positions.

Nothing here is investment advice. Trading carries a significant risk of capital loss.