Average Share Price Calculator

Use this calculator to estimate how another purchase could change the average price paid for your shares. It combines your existing holding with the proposed purchase and includes any dealing fees you enter.

How the calculation works

The calculator first works out the cost of your existing holding from the number of shares and their existing average price.

It then calculates the cost of the proposed investment using the number of new shares, their purchase price and dealing fees. These costs are added together and divided by the total number of shares:

New average share price = total cost basis ÷ total shares

The results show your new average share price, total number of shares, total cost basis and the cost of the proposed investment.

If you provide a current market price, the calculator will also show an estimated unrealised gain or loss. This result is only displayed when a current market price is supplied.

The calculator handles an empty existing holding and zero new shares safely.

Important information

• This calculator uses a simple weighted average calculation.
• It is not an HMRC share-pooling or Capital Gains Tax calculation.
• Any unrealised gain or loss is shown only when you enter a current market price.
• Results depend on the figures you enter and are estimates for guidance only.
• Tax treatment depends on individual circumstances and can change.
• This calculator does not provide personalised financial, investment or tax advice.