Stock Average Cost Calculator - Average Down or Up and Find Your New Cost Basis
Stock Average Cost Calculator
See your new average price after you buy more
Average Down or Up
Buying more at a lower price lowers your average cost, and buying at a higher price raises it. The result shows your new average and how much it changed.
Work Backwards
Enter the average price you would like and the calculator tells you how many extra shares at the new price would get you there.
See Profit or Loss
Add the current price to see the value of the whole position and what you would make or lose.
Private
The numbers stay in your browser and are not stored.
How Average Cost Works
Your average cost per share is the total amount you paid, including fees, divided by the number of shares you own. If you own 100 shares bought at 50 and buy 50 more at 40, you have spent 7,000 for 150 shares, so the average is 46.67. The average is the price the stock must reach for you to break even on that position, before selling costs.
Averaging down lowers your break-even price, but it also puts more money into a stock that is falling, which can turn a small loss into a larger one if it keeps dropping. It works best for a company you still believe in and have a plan for. This calculator does the arithmetic only. It is not advice, and it does not account for taxes, which in many places treat each purchase lot separately.
Key Takeaways
- Include fees: Commissions on the new purchase are added to the cost, so enter them to see the true average.
- Lots matter for tax: Tax rules often use specific purchase lots, not the blended average shown here.
- Related calculators: See also the Stock Profit Calculator and the Dollar-Cost Averaging (DCA) Calculator.