Updated September 2026
When a position is down, there are really only three choices: hold as-is, add more (averaging down), or sell and cut the loss. This calculator computes what your numbers would become under the "add more" path — but it has no way to tell you which path is right for a specific situation, because that depends on things outside any formula: your read on the asset, your risk tolerance, and your existing exposure. This page is a framework for thinking through that decision more carefully, not a recommendation.
The single most useful question to ask before adding to a losing position is whether anything about your original reason for buying it has actually changed, separate from the price itself moving. There are three honest answers:
A question that's easy to skip: regardless of what you think about the asset, does adding to this position push it past a size you'd be comfortable with as a share of your overall portfolio? Averaging down mechanically means putting more capital into something that has already moved against you — a decision that increases concentration exactly when the position has already shown it can be wrong. If the position was already at or near your personal size limit before the drop, "it's a better price now" doesn't change the concentration math; it may make it worse, since you're now considering an even larger dollar commitment to reach the same target percentage of your portfolio you'd have hit with a smaller add at the original price.
Run the numbers for the position as it stands, and again for the position with the proposed add, using the calculator. Two things are worth looking at side by side: how much lower does the break-even actually move (sometimes it's less than intuition suggests — see the worked example for how the effect depends on relative lot sizes), and how much larger does your total dollar exposure become. A modest break-even improvement bought with a large increase in exposure is a different trade-off than a large break-even improvement from a small additional commitment.
A commonly cited sanity check: ignoring that you already own this position, would you buy it today, at today's price, as a brand-new decision? If yes, adding to your existing position and opening a small new position are economically the same choice, and averaging down is at least consistent with your standalone view of the asset at current prices. If the honest answer is no — you wouldn't buy it fresh today — then the only reason to add is the existing position itself, which is a description of the sunk-cost reasoning covered in why averaging down can go wrong, not an independent case for the purchase.
Some situations don't need an elaborate framework: if the reason you bought the asset has been directly contradicted by new information (the company's competitive position genuinely eroded, the project's stated plans changed materially, the thesis you wrote down at purchase time turned out to be wrong), continuing to add capital doesn't fix that — it just means more capital is exposed to a thesis you no longer believe. In that situation, cutting the loss and redeploying elsewhere is the more disciplined choice, even though it's the psychologically harder one to execute, precisely because it means accepting the loss is real rather than treating a lower average cost as a way to avoid acknowledging it.
The choice isn't always binary. A smaller add than originally considered, or a partial sale rather than a full exit, can be reasonable ways to express genuine uncertainty rather than forcing a decision to look more confident than it is. The calculator handles any size add or the multi-lot view for tracking a position over several partial moves — the framework above is about sizing the decision honestly, not about which button to click.
Is there a rule of thumb for when to average down vs. cut losses? No single rule applies across situations — this page is a framework for structuring the question, not a formula that outputs an answer. The inputs (has the thesis changed, does this fit your risk limits, would you buy it fresh today) are things only you can assess for a specific position.
Does this calculator recommend either path? No — it computes the arithmetic outcome of adding to a position (new average cost, break-even, exposure) so that whichever decision you make is at least made with accurate numbers. Not financial advice.