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Calculate average cost across multiple purchases.
Stock Average Calculator is a free browser-based tool that helps you calculate average cost across multiple purchases. It is part of ToolsMonk's stock market tools collection, so you can finish the job without downloading software, creating an account, or jumping between multiple websites.
This tool is especially useful for workflows such as finding your true average cost after buying a stock at several prices, working out the new average if you average down on a falling stock, and checking the break-even price across all your lots. Because it runs directly in your browser, you can use it on desktop, tablet, or mobile while keeping the process fast and easy for one-off tasks as well as repeat work.
Stock Average Calculator is designed for people who want a practical, privacy-friendly workflow with instant results inside the larger ToolsMonk library.
Enter each purchase as a price and quantity
Add as many lots as you have
See total shares, total invested, and the weighted average buy price
Add a hypothetical lot to see how it changes your average
Calculates your average buy price across multiple purchases of a stock
Add several buy lots at different prices and quantities
Shows total shares, total invested, and the weighted average price
Useful for averaging down or up positions
Runs in your browser — your holdings stay on your device
Free, with no signup
Finding your true average cost after buying a stock at several prices
Working out the new average if you average down on a falling stock
Checking the break-even price across all your lots
Planning an additional purchase to reach a target average
Stock Average Calculator is a powerful free online tool available on ToolsMonk that helps you calculate average cost across multiple purchases. Whether you're a professional, student, or casual user, our stock average calculator provides instant, accurate results right in your browser without requiring any software installation or account creation.
As part of our Stock Market Tools collection, this tool is designed with simplicity and power in mind. All processing happens client-side, ensuring your data remains completely private and secure. The tool works seamlessly across all modern browsers on desktop, tablet, and mobile devices.
Stock Average Calculator finds your true average buy price across multiple purchases of the same stock — a weighted average of total money invested divided by total shares, which is your real cost basis and break-even point.
The key insight is that it's weighted, not a simple average of prices. Because you typically buy different quantities at different prices, the larger lots pull your average toward their price. Buying 10 shares at $100 and 30 at $80 averages to $85, not $90 — and that $85 is the number that actually matters for break-even.
It's the standard tool for 'averaging down' — buying more after a price drop to lower your average cost. The calculator shows the new average clearly, but it's worth remembering that averaging down also increases your exposure to a stock that's already falling, so it's a risk decision, not just arithmetic.
Add a hypothetical lot to preview how a planned purchase would shift your average and break-even before committing. Everything runs in your browser, so your holdings stay private, and the output is an analysis aid rather than financial advice. Pair it with the Profit/Loss calculator to review outcomes.
Your average cost is a weighted figure — quantity at each price matters, so don't eyeball a simple midpoint
Use a hypothetical lot to preview your new break-even before averaging down or up
Averaging down lowers your cost but raises your exposure to a falling stock — weigh the risk, not just the math
Common questions about this tool, its workflow, and what to expect before you use it.
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