Stock Average Calculator
Find your stock cost basis after multiple buys at different prices. Get average price per share, total cost, and unrealized profit or loss.
About This Calculator
The Stock Average Calculator helps investors determine their weighted average purchase price (cost basis) when buying shares of the same stock at different prices. Whether you are averaging down after a price drop or building a position over time, knowing your exact cost basis is essential for making informed decisions and calculating capital gains for tax purposes.
The calculation uses the weighted average formula: Cost Basis = (p₁ × q₁ + p₂ × q₂ + ... + pᵢ × qᵢ) / (q₁ + q₂ + ... + qᵢ), where each purchase price is weighted by the number of shares bought at that price. This ensures the average accurately reflects how much you truly paid per share. Simply add your buy transactions, optionally enter the current market price, and the calculator instantly computes total shares, total cost, average price, current value, and profit or loss with percentage return.
Regional Notes
India: Long-term capital gains (LTCG) on listed equity shares held for more than 12 months are taxed at 10% on gains exceeding ₹1 lakh per financial year (without indexation). Short-term capital gains (STCG) on shares held for 12 months or less are taxed at 15%. Cost basis is calculated using the first-in-first-out (FIFO) method by default for Indian tax purposes.
US: The IRS allows three cost basis methods: FIFO (first-in-first-out), specific identification, and average cost (for mutual funds only). For stocks, FIFO is the default method. Shares held over 1 year qualify for long-term capital gains rates (0%, 15%, or 20% depending on taxable income). Short-term gains are taxed as ordinary income. The cost basis adjusts for stock splits and dividends.
UK: HMRC uses a "share pool" or "section 104 holding" method where all shares of the same class in the same company are pooled and a single average cost is calculated. Capital gains above the annual exempt amount (£3,000 for 2025-26) are taxed at 10% for basic rate taxpayers and 20% for higher rate taxpayers.
Frequently Asked Questions
What is stock average or cost basis?
Stock average (cost basis) is the weighted average price you paid per share when buying the same stock at different prices. It is calculated by dividing the total cost of all shares by the total number of shares owned.
How do I calculate average stock price after multiple buys?
To calculate average stock price, multiply shares by price for each purchase, add all results to get total cost, then divide by total shares. For example, buy 10 shares at ₹150 and 15 shares at ₹130: total cost = ₹3,450, total shares = 25, average price = ₹138 per share.
Why is knowing cost basis important for tax reporting?
Cost basis determines your capital gain or loss when you sell shares. In India, LTCG above ₹1 lakh on stocks held over 12 months is taxed at 10% without indexation. In the US, shares held over 1 year qualify for lower long-term capital gains rates (0%, 15%, or 20% depending on income). In the UK, capital gains above the annual exemption (£3,000 for 2025-26) are taxed at 10% (basic rate) or 20% (higher rate).
Can I average down my stock cost basis?
Yes, averaging down means buying additional shares at a lower price than your original purchase, which reduces your overall cost basis per share. This strategy lowers the price needed to break even but requires conviction that the stock will rebound.
What is the formula for weighted average stock price?
Weighted average stock price = (p₁ × q₁ + p₂ × q₂ + ... + pᵢ × qᵢ) / (q₁ + q₂ + ... + qᵢ), where p is price per share and q is number of shares for each buy. This gives you the true cost basis accounting for different position sizes.
Does the stock average calculator include brokerage fees?
This basic calculator does not include brokerage fees, taxes, or other transaction costs. For a more comprehensive analysis including fees, use our full Stock Calculator which factors in commissions and additional charges.
How do I calculate profit or loss on my stock investment?
Stock profit or loss = (Current Market Price - Cost Basis) × Total Shares. Enter the current market price in this calculator to see your unrealized profit or loss, both in absolute terms and as a percentage return.