Stock Average Price Calculator

About this calculator

When you buy shares of the same stock at different prices over time, your true cost basis is not any single purchase price but the weighted average across all buys: Average price = Σ(price_i × shares_i) / Σ(shares_i) — each purchase’s price is weighted by how many shares it added, so a larger buy pulls the average toward its price more than a small one does.

This blended cost is what investors use to calculate their actual break-even price, gains or losses, and cost basis for tax reporting, and it’s the number that matters after averaging down (buying more shares when the price drops) or dollar-cost averaging into a position over time — not the price of your first or most recent trade. This calculator takes up to three buy prices with their share counts and returns the total shares purchased, total cost, and blended average price per share.