Free tool · no sign-up

Stock average down calculator

Averaging down changes your cost basis, and the number that matters afterwards is not what you paid first. Enter each lot and this returns the blended average, which is the price the position has to clear before it is green.

Up to three lots. Leave a row blank to ignore it. Nothing you type is sent anywhere; the maths runs in your browser.

How it works

The blended average is total cost divided by total shares, not the midpoint of the two prices. Buying 100 at $50 and 100 at $40 gives $45 because the lots are equal. Buy 100 at $50 and 300 at $40 and the average is $42.50, because the larger lot pulls it further.

To break even is how far the stock has to move from your most recent price to reach that average. It is the honest version of the question averaging down is usually asked to answer.

Averaging down lowers your average and raises your size at the same time. The second number is the one that decides what a further move costs you, which is why position size belongs in the same conversation.

Common questions

Does averaging down lower my break-even price?

Yes, it lowers the average cost per share, so the position turns green sooner than it would have. It also increases the number of shares exposed, so a further decline costs more per point than it did before.

Should the calculator include commissions?

Add them into the lot price if you want cost basis after fees. Most US brokers charge nothing on stock trades now, so the difference is usually immaterial for equities and material for options.

Is this the same as dollar cost averaging?

No. Dollar cost averaging is buying on a fixed schedule regardless of price. Averaging down is adding specifically because the price fell, which is a different decision and carries different risk.

SES Technology Ventures LLC. These tools are for arithmetic, not advice.