The stock average calculator combines an existing share position with a new purchase to estimate the new weighted average cost per share. It also shows total shares, total invested amount and the change from the old average price.

How it works

Enter the existing quantity and average cost, then the quantity and price of the new purchase. The calculator adds the cost of both lots and divides by the combined number of shares.

The formula

New average = (old quantity × old average + new quantity × new price) ÷ (old quantity + new quantity). Average change = old average − new average.

Quantities and prices must be non-negative and the combined quantity must be greater than zero. The result is a weighted cost average only. If the new purchase price is above the old average, the displayed average reduction can be negative because the new average has increased.

Worked example

100 shares at an average cost of 35 plus 50 shares at 28 produce total cost 4,900 across 150 shares. The new average is 32.6667 and the change from the old average is 2.3333.

This calculator is a mathematical position-cost tool, not a recommendation to buy additional shares. Averaging down can increase total exposure and losses if the investment continues to decline.

Frequently asked questions

Does buying more shares always lower my average cost?

No. The average falls only when the new purchase price is below the existing average. Buying above the existing average raises the weighted average.

Does the calculation include commissions or taxes?

No. It uses only the quantities and prices entered. Add transaction costs to the effective purchase cost separately if they are relevant.

Does a lower average cost mean the investment is safer?

No. The calculation describes cost basis only and does not measure market risk, business quality or future return.

Saudi Stock Average Calculator

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