Stock Average Calculator
Buying more shares at a lower price changes what you effectively paid for your whole holding — but the new figure is not a simple midpoint. This stock average calculator blends both purchases into one weighted average buy price, shows the combined amount you have put in, and updates the moment you type, so you can sanity-check an averaging-down decision before you place the order.
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How to use this calculator
- Type the number of shares from your first purchase and the price you paid per share.
- Add the second lot — usually the top-up you are considering at today's lower rate.
- Read the weighted average on the right; it already accounts for lot sizes, unlike a simple midpoint.
- Check total invested against the cash you actually want deployed in this one stock.
- Change either price to preview how the next dip would move your break-even level.
The formula behind it
The tool uses the weighted average formula: multiply each lot's share count by its purchase price, add those rupee amounts together, then divide by the combined share count. Written out, average price = (Q1 × P1 + Q2 × P2) ÷ (Q1 + Q2). The weighting matters because a bigger lot drags the average towards its own price far more than a small one does. Prices here are clean trade prices — brokerage, taxes and levies sit on top of your true break-even, which is why the result is labelled a trade-price average.
Worked example
An investor holds a mid-cap IT stock that has slid over a rough quarter. She had bought 120 shares at ₹1,410 earlier in the year. With the stock now trading near ₹1,265, she doubles down with 180 more shares rather than trying to time an exact bottom.
| First purchase | 120 shares × ₹1,410 |
|---|---|
| Second purchase | 180 shares × ₹1,265 |
Step by step
- 120 × ₹1,410 = ₹1,69,200
- 180 × ₹1,265 = ₹2,27,700
- Total invested = ₹1,69,200 + ₹2,27,700 = ₹3,96,900
- Total shares = 120 + 180 = 300
- Average = ₹3,96,900 ÷ 300 = ₹1,323.00
Her weighted average buy price lands at ₹1,323 per share — below her original ₹1,410 entry, so any future rally past ₹1,323 puts the whole position in profit.
Frequently asked questions
Why is my average not simply midway between the two prices?
Because lots are rarely equal. The average is weighted by share counts, so whichever purchase involved more money pulls the result towards itself. Only when both lots have identical share counts does the plain midpoint match the weighted figure.
Does this average include brokerage and other charges?
No. The calculation uses clean trade prices, which matches the buy average most broker apps display. Your real break-even sits slightly higher once brokerage, STT and exchange charges are loaded onto the buying leg.
I averaged up instead of down — does the same math work?
Yes. The formula never cares whether the second price is lower or higher. Adding shares above your original entry lifts the weighted average towards the newer, pricier lot exactly the same way.
Can I combine three or more purchases?
The calculator takes two lots side by side, but the principle scales: multiply every lot's quantity by its price, sum all of it, and divide by total shares. Chain the tool twice to fold a third lot into an existing average.
What is the difference between my average price and break-even?
Average price is what you paid per share across all lots. Break-even is the selling price that repays your entire position including selling-side costs. Keep a small cushion above the average so statutory charges do not turn a paper profit into a flat or negative net result.
What the average price actually controls
Your weighted average is the hinge every later decision swings on. Stop-loss levels, partial-exit plans and dividend yield calculations all start from that single number, which is why guessing it from memory is risky after even two purchases. Averaging down by ten percent in price does not move your average by ten percent — the shift depends entirely on how large the new lot is relative to the old one, and running the numbers beforehand tells you whether the planned top-up is big enough to matter.
There is also a portfolio-level angle. Money sunk into rescuing one falling stock is money not earning anything elsewhere, so experienced investors compare the improved average against a simple alternative: starting a fresh position in a healthier name. The arithmetic here gives you the honest input for that comparison rather than an emotional attachment to defending an earlier decision.
Averaging down versus averaging up
Averaging down feels natural to Indian retail investors raised on 'buy the dip', but it concentrates risk in a thesis that is already being questioned by the market. A disciplined version sets the second lot size before the fall ever happens — for instance, matching rupee amounts rather than share counts — so the rescue cannot grow endlessly. Using this calculator before placing the order turns that discipline concrete: you see exactly how much the average improves per rupee added, and can cap the lot where improvement flattens out.
Averaging up gets less attention, even though adding shares only when the market is confirming your original thesis avoids the classic trap of committing fresh capital against a falling price. The arithmetic is identical — only the direction of the second price changes — yet the discipline required differs sharply: you must sell part of the position just as readily when confirmation disappears. Whichever style you follow, record each lot's date and price; six months later, the weighted average plus those dates also decide which tax bucket your shares fall under when you finally sell.
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Data sources & verification dates
- Income Tax Department — Section 45 & Weighted Cost Basis for Shares — verified as of 2026-08-26
- SEBI Investor Portal — Equity Averaging & Risk Guidelines — verified as of 2026-08-26
- NSE India — First-Time Investor FAQs & Order Execution Rules — verified as of 2026-08-26
stockcalculator.in Research Desk — Editorial team; verifies every figure against official sources before publishing
Last updated . Figures are re-verified against official sources on every revision — see our methodology.
Disclaimer
Calculations on stockcalculator.in run entirely in your browser using the inputs you provide. Figures shown are estimates for education and planning only. We are not SEBI-registered investment advisers and nothing on this site is investment advice. Verify anything material with your broker, fund house, or a qualified adviser before acting on it.