Average cost calculator — average down with the numbers in front of you
Enter each buy and see the average, the break-even after fees and the P&L at the live price. Then ask the harder question: how much more money does it take to pull the average to the number you have in mind?
— —
—
—
—
Enter a target and a buy price above.
The arithmetic behind the number
Average cost = total dollars spent ÷ total units. Fees are part of the dollars spent, which is why the break-even sits above the average: you must also pay the fee on the way out, so break-even = average ÷ (1 − sell fee). With the default 0.1% and 0.1% fees, a $55,000 average breaks even at about $55,110.
The target-average solver rearranges the same formula. Holding U units at average A, buying X units at price P gives a new average of (A·U + P·X) ÷ (U + X). Set that equal to the target T and solve: X = U·(A − T) ÷ (T − P). The closer the target is to the buy price, the more you must add — halving the distance to break-even roughly doubles the position.
Averaging down is a sizing decision
Every extra buy lowers the average and raises the exposure. Before adding, put the new total through the portfolio tracker to see the weight it would have, and through the drawdown calculator to see what another leg down would cost. Dollar-cost averaging on a schedule is the disciplined version of the same maths; averaging down after a loss is the emotional one. The formula does not care which you are doing — you should.
Questions people ask
How is average cost calculated?
Total dollars spent divided by total units bought. Two buys of 0.1 BTC at $60,000 and 0.1 BTC at $50,000 cost $11,000 for 0.2 BTC, so the average is $55,000. Fees raise the cost side and therefore the break-even.
What is averaging down?
Buying more after the price falls so the average cost drops. It lowers the price you need to get back to even, but it also puts more money into a position that is already losing — it is a sizing decision dressed up as a discount, and it is how many first accounts end up 80% in one coin. Use the target-average solver to see the money involved before deciding.
How much do I need to buy to bring my average to a target?
If you hold U units at average A and can buy at price P, the units X that bring the average to T satisfy (A·U + P·X) ÷ (U + X) = T, so X = U·(A − T) ÷ (T − P). It only works when P is below T and T is below A. The calculator solves it and shows the dollars.
Does the price update live?
If you pick a coin from the list, the current price ticks from the same exchange WebSocket that powers the site's live prices, so the P&L line moves with the market. You can also type any price manually.
Is my data saved?
The rows stay in this browser only (localStorage) so you can come back to them; nothing is uploaded. Clear them with the button.