Average cost calculator
After a few purchases at different prices, most people cannot say what they actually paid on average. This works it out.
How the average is weighted
It is total spent ÷ total units, not the average of the prices. Those differ whenever the buys were different sizes, and the difference is usually larger than people expect. A large buy at a bad price dominates the basis regardless of how many small good ones followed.
Break-even
Break-even equals the weighted average cost, before fees. Add both sides’ trading fees and the real figure is slightly higher — the trading fee impact tool covers that.
What this does not model
Nothing here is a tax cost basis. Jurisdictions differ on whether you may use average cost at all, and several require FIFO or specific identification instead. Do not use this figure on a tax return.
