About avgdown

avgdown is a free web calculator that shows how your average cost per share changes when you buy more of a stock you already own.

What it does

• Enter how many shares you plan to add and see your new average cost and how much it changes.
• Enter a target average and see how many shares at today's price would get you there.
• See your average including commissions and your break-even sell price after fees and sell taxes. Presets are included for US and Korean stocks, and every rate can be edited.
• Copy a link to your result to open it on another device or share it.

The guides explain the formulas with worked examples.

Everything runs in your browser

All calculations happen in the browser you are using. The numbers you enter are not sent to a server, and there are no accounts. Details are in the privacy policy.

Not investment advice

avgdown is a calculation tool. Its results and guides are general information only. They are not a recommendation to buy or sell any security and are not investment, tax or legal advice. Fees and tax rules change, so your broker and official sources are the authority for actual trades. You are responsible for your own decisions.

Contact

Bug reports and feedback are welcome through the contact page.