Average Down / Cost Basis Calculator
Buying more of a position at a lower price pulls your average cost down — but it also puts more money into a trade that's already moving against you. This shows your new average, your total exposure, and exactly how far the price has to recover for you to break even.
- • New average = (shares₁ × price₁ + shares₂ × price₂) ÷ (shares₁ + shares₂).
- • Move to break even = new average ÷ latest price − 1.
Worked example: 100 shares at $100 plus 100 more at $80 gives a $90 average — so from $80 the price needs to rise +12.5% just to break even.
A lower average is not the same as a good trade — averaging down a loser can be throwing good money after bad. Decide your risk before you add, not after. Educational tool, not advice.
A calculator shows what a rule should do on paper. Whether a strategy actually beats simply buying and holding — costs on, losses shown, no hindsight — is a different question, and the only one that pays. Test one on real data, free, no sign-up.