Position size calculator for stocks and lots
How many shares or lots fit the loss you can accept on one trade.
Result
The risk budget is ₹5,000.00. The distance between the two levels is ₹5.00. After rounding down, 1,000 units fit the budget. Their position value is ₹2,50,000.00. Value and the risk budget are different amounts.
Risk against capital
- At risk at this quantity₹5,000.00
- Rest of your capital₹4,95,000.00
If the stop-loss is reached, ₹5,000.00 of the ₹5,00,000.00 capital you entered is lost — 1.00% of it.
Position value against capital
- Position value₹2,50,000.00
- Capital not deployed₹2,50,000.00
The position is worth ₹2,50,000.00 — 50.0% of the capital you entered. Quantity and entry price alone set this figure. A margin product can require less cash up front.
The position these figures give
- Capital you entered₹5,00,000.00
- Risk budget · 1% of that capital₹5,000.00
- Entry–stop distance · entry to stop-loss distance₹5.00
- Capital the position needs · quantity × entry price₹2,50,000.00
- At risk at this quantity · what the stop-loss actually costs₹5,000.00
- Reward against risk · add a target price to fill this in—
- Quantity · rounded down to your lot multiple1,000
Rounding down to the lot multiple is why the amount at risk is never more than the budget. It is arithmetic on figures you supplied — this page does not suggest a capital, a percentage or a stop-loss distance.
Formula: quantity = floor( (capital × risk%) ÷ |entry − stop| ) rounded down to your lot multiple, so the actual risk never exceeds your budget.
Each file lists the source and the check date for every rate. The CSV comes as two files, the figures and their sources.
The link carries only these inputs. Saved inputs stay in this browser only, and are off until you turn them on.
Try one change
Each button changes exactly one input and says what that did to the headline figure. Reset undoes it.
Continue: how often must this quantity be right to finish level? → Carries the quantity and the level you entered into the break-even frequency calculator. The bracket and charges are set there.
What this calculator does and does not do
What this calculator does
- Turns a capital figure, a risk percentage and a stop distance into a whole quantity, rounded down to your lot or share multiple.
- Shows the amount actually at risk after that rounding, which is always a little below the budget rather than equal to it.
- Describes the reward-to-risk of the two distances you entered, if you enter a target.
What it does not do
- Suggest where to place a stop, what to trade, or what fraction of your capital to risk. No point on the slider is marked or preferred.
- Account for gaps, slippage or partial fills. The realised loss can exceed the budgeted one.
- Know what margin a broker will ask for. The capital required figure is the position's value, not the cash needed to carry it.
Show the method and assumptions
The method
- Risk budget = capital × risk per trade (%).
- Entry–stop distance = the gap between the entry price and the stop price.
- Quantity = risk budget ÷ entry–stop distance, rounded down to your lot size.
- Position value = quantity × entry price.
What it assumes
- The stop fills exactly at the price you typed.
- Gaps, slippage and charges can make a real loss bigger.
- Rounding down keeps the risk inside your budget.
Sources, effective dates and exclusions
- Calculated on
- today
Published lot sizes are the ones in force today.
Source: NSE and BSE index derivative contract-size circulars
- Rules in force from
- 28 Oct 2025
- Source published
- 3 Oct 2025
- Last reviewed
- 5 Oct 2026
Not included
- Live market prices. Every price here is one you type.
- The margin your broker blocks.
What could change this?
- The distance between the two levels. Halve it and the quantity doubles. The risk budget does not move.
- The lot multiple. Rounding down to a whole lot can leave part of the budget unused, and a budget smaller than one lot gives a quantity of zero.
- The risk share you choose. The calculator never suggests it. Change it and everything below it scales.
- Gaps, slippage and partial fills. The planned risk assumes an exit exactly at the level you entered. The market does not promise that.
The three steps behind the quantity
Step 1. Risk budget
Your capital multiplied by the risk-per-trade percentage you chose. It is the rupee amount the rest of the calculation is sized to.
Step 2. Entry–stop distance
The distance between the entry price and the stop-loss price you entered. It is an absolute value, so it is the same in either direction.
Step 3. Quantity
Divide the budget by the entry-to-stop distance. Round down to your or share multiple to keep planned risk inside the budget.
How position sizing works
Risk-based position sizing turns a chosen risk budget into a quantity. The budget is a share of your capital, such as 1% or 2%. Find the distance between the opening price and the stop-loss. Divide the budget by that distance. Then round down to your lot or share multiple. At that stop price, the planned risk stays inside the budget.
Reading the two bars
The first bar splits your capital three ways. There is the amount at risk if the stop-loss is reached, the part of the budget that lot-rounding leaves unused, and the remainder. The second bar compares the position value with the same capital. A position can be worth more than the capital you entered. That is what and leverage do. When it happens, the bar is drawn to the larger of the two figures. The uncovered part then gets its own segment, rather than being squeezed inside a full bar. Every figure in both bars is also printed as text beside it.
Reward-to-risk
If you add a target price, the tool shows the reward-to-risk ratio. That is the distance to the target divided by the distance to the stop. It is a description of the two distances you entered. It is not a forecast, and not a suggestion to take any trade.
Where this appears in NISM Series VIII
Unit VII of the NISM-Series-VIII: Equity Derivatives curriculum is Introduction to Clearing and Settlement System. It covers risk management, SPAN margining, mark-to-market and position limits. That is the exchange side of how much exposure a participant may carry. This calculator works the same idea from the participant's own capital. It converts the result into whole lots, which is the market lot idea from Unit VI (Trading Mechanism). See the NISM Series VIII syllabus and exam format.
What it does not do
It does not tell you where to place a stop, what to buy or sell, what percentage of your capital to risk, or whether a trade is suitable for you. The percentage on the slider is yours to set and no value on it is marked or preferred. Market gaps, and partial fills mean the actual loss can differ from the budgeted figure.
See how an order meets the book: Market, limit and stop orders: what each one controls compares all three order types. A price touching a level and an order filling there are separate events.
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Open →A worked example: where the quantity comes from
Capital ₹5,00,000, one per cent of it at risk, an entry at ₹250 and a stop at ₹245. The share can be bought one at a time. Three divisions, in order:
Risk budget = 5,00,000 × 1% = ₹5,000 Entry–stop distance = 250 − 245 = ₹5 Quantity = 5,000 ÷ 5 = 1,000 shares
Now look at what that position is worth: 1,000 × ₹250 = ₹2,50,000, which is half the capital, for a risk of one per cent of it. That gap is the part people find surprising, and it is the whole point of the second bar above. The value of the position follows the distance to the stop, not the risk figure.
Widen the stop to ₹240 and the distance doubles to ₹10. Quantity halves to 500 and position value halves to ₹1,25,000. The planned risk stays at ₹5,000. The view is unchanged. Only the stop level moved.
Widen it far enough and the division stops having an answer that can be traded. Capital ₹50,000, half a per cent of it at risk, an entry at ₹2,400 and a stop at ₹2,100:
Risk budget = 50,000 × 0.5% = ₹250 Entry–stop distance = 2,400 − 2,100 = ₹300 Quantity = 250 ÷ 300 = 0.83 → 0
A single unit puts ₹300 at risk and the budget is ₹250. No whole quantity fits inside it. The answer is none, and that is what the calculator returns. It gives a quantity of zero with the reason printed beside it, rather than a one rounded up out of a fraction. Rounding up would overshoot the budget by a fifth, on the one figure the whole calculation exists to hold. Three things could change instead: the capital, the share of it at risk, or the distance to the stop. Choosing between them is not arithmetic, and this page does not do it.
Common mistakes
- Reading the quantity as a recommendation. It is the largest whole number of units that keeps the modelled loss at the stop inside the budget — arithmetic on the levels you entered, not a view on the trade.
- Reading the risk at this quantity as the most you can lose. It assumes the exit fills at the stop. A gap, slippage and the charges on both legs are all outside it.
- Assuming the position value must fit inside the capital. The calculator sizes by risk, so the value of the position can exceed the capital you entered — that is a fact about the arithmetic, not a margin calculation.
Position sizing FAQ
How do I calculate position size from risk per trade?
Position size in shares equals the rupee amount you are risking on the trade divided by the per-share stop-loss distance (entry price minus stop-loss level). For example, risking Rs 5,000 with a Rs 25 per-share stop distance gives 5,000 / 25 = 200 shares. The rupee risk itself is typically derived as a chosen percentage of total trading capital.
What is the 1% / 2% rule in position sizing?
The 1% / 2% rule is a convention where the rupee amount risked on a single trade is capped at 1% or 2% of total trading capital, defining the loss taken if the stop-loss is reached. On Rs 5,00,000 of capital, a 1% rule sets per-trade risk at Rs 5,000 and a 2% rule at Rs 10,000. It is a capital-allocation formula and does not predict outcomes.
How does the stop-loss distance affect quantity?
For a fixed rupee risk, quantity is inversely proportional to the per-share stop-loss distance, since quantity equals rupee risk divided by that distance. A wider stop distance produces a smaller share count, while a narrower stop distance produces a larger one. Doubling the stop distance halves the calculated quantity for the same risk budget.
What is reward-to-risk ratio and how is it calculated?
Reward-to-risk ratio compares the per-share distance from entry to a target against the per-share distance from entry to the stop-loss, expressed as a multiple such as 2:1. It is computed as (target price minus entry price) divided by (entry price minus stop-loss level) for a long position. The ratio is a description of the trade's geometry, not a forecast of which level is reached.
How is position size calculated for NSE F&O contracts that trade in lots?
In NSE F&O, instruments trade in fixed lot sizes, so the share-based quantity from the risk formula is converted to whole lots by dividing by the lot size and rounding down. If the risk formula allows 240 units and the lot size is 75, that is 240 / 75 = 3.2, which rounds to 3 whole lots. Because lots are indivisible, the realised risk per lot can differ from the exact rupee budget.
What does notional position value mean and how does it differ from risk?
Notional position value is quantity multiplied by entry price, representing the total capital deployed or exposure, whereas risk is quantity multiplied by the per-share stop-loss distance. A trade can have a large notional value but a small defined risk if the stop distance is narrow. The two figures answer different questions: capital committed versus amount exposed to loss at the stop.
Understand the idea
Read the short lesson behind this tool.
Where to go from here
Why quantity is a division rather than a measure of conviction, and how steeply it falls away as the distance to the level widens.
Read the lesson Then thisBreak-even win rate calculatorThe quantity above sets what each round trip costs. This turns that cost into a requirement: how often the trade has to come good simply to finish level.
OpenPaper Trading Try it on the practice trading desk
Last checked on 5 October 2026.
Lot size is the number of units of the underlying that one derivatives contract stands for.
Read moreMargin is the money a participant must keep in place to carry a leveraged position.
Read moreImpact cost is the difference between the price shown on screen and the price a trade is actually filled at.
Read more