AVERAGE COST CALCULATOR

Stock Average Cost Calculator

See your new average cost after another purchase.
Or work out how much you need to reach a target average.

Your numbers

New average cost

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Enter your current position and new purchase.

Understand your total investment

Existing cost: —
Additional cost: —
Total cost: —
Total quantity: —

Fees, taxes and currency conversion are excluded. Displayed results are rounded to 8 decimal places.

How to calculate average cost for stocks and crypto

Average cost is weighted by quantity, rather than a simple average of two prices. This calculator combines your existing position with one additional purchase.

New average = (current average × current quantity + purchase price × purchase quantity) ÷ total quantity

For example, if you own 10 shares at $100 and buy 10 more at $80, your total cost is $1,800 for 20 shares. Your new average cost is $90 per share.

How much do I need to reach my target average?

Choose Target average and enter your current average, quantity, new purchase price and target. The result shows the additional quantity and cost required.

Additional quantity = current quantity × (current average − target average) ÷ (target average − purchase price)

Your target must lie between your current average and the new purchase price. Reaching exactly the purchase price is not possible with a finite additional quantity. Whole-share mode rounds the required quantity up and shows the resulting average. A target equal to your current average requires no additional purchase.

Frequently asked questions

Can I use this for stocks and crypto?

Yes, when purchasing the same asset in the same currency. Enter decimal quantities for fractional shares or crypto. This tool does not calculate futures leverage, liquidation prices or funding payments.

Does averaging down immediately reduce my loss?

No. An additional purchase increases your position and invested capital. Further price declines can increase your total loss. This tool calculates a scenario and does not recommend buying.

Why does my broker show a different average cost?

Execution prices, fees, exchange rates, stock splits and rounding may differ. This tool uses only your entered prices and quantities. It is not a tax cost-basis calculator.

Results describe your assumptions and do not predict or guarantee returns. Your inputs are not saved to our server.