What this calculator does
Compare your existing average purchase price with the new weighted average after an additional stock purchase. InvestCalc shows the before-and-after average, the change in average cost, total shares and total invested amount.
Try the Stock Average Calculator
Enter your own figures and explore an estimate in the InvestCalc calculator.
Open calculator ↗Compare your existing and new average price
The result highlights your existing average cost per share beside the new average cost after the additional purchase. It also shows the absolute and percentage change, so you can see exactly how the new transaction changes your average entry price.
How is the average share price calculated?
Your average cost per share is calculated by dividing the total amount invested across purchases by the total number of shares. Each purchase contributes according to its quantity and price.
Formula
New average price = (Existing shares × Existing average price + Additional shares × New purchase price) ÷ Total shares after purchase.
What this estimate excludes
Brokerage, exchange fees, taxes, currency conversion charges and other transaction costs are not included unless you add them separately to your inputs.
When should you use it?
Use the tool to understand how a hypothetical additional purchase changes your average cost. A lower average cost does not guarantee a profitable investment or make a stock fundamentally stronger.
Frequently asked questions
Does averaging down guarantee a profit?
No. It changes the average cost of your position; it does not reduce the underlying business or market risk.
Are brokerage and taxes included?
No. The result is a basic estimate before transaction costs and taxes.