Steps
Break each buy into an amount and a price: coins from that buy = amount ÷ price.
Add all the coin amounts to get coins held, then divide total invested by coins held to get the average cost.
The same method applies to buys of different sizes: the larger buy carries more weight in the average.
Formulas
amount i ÷ price isum of coins across all buystotal invested ÷ coins heldcoins held × current price − total investedWorked example (recompute it yourself)
Three buys: 1,200 USDT at 2,600, 800 USDT at 2,400, 1,500 USDT at 2,200:
Coins per buy = 0.46153846 / 0.33333333 / 0.68181818, so coins held = 1.47668998 ETH and total invested = 3,500 USDT.
Average cost = 3,500 ÷ 1.47668998 ≈ 2,370.17 USDT, below the simple average of the three buy prices, 2,400 USDT.
At a current price of 2,471 USDT, position value = 1.47668998 × 2,471 ≈ 3,648.90 USDT, an unrealised gain of about +148.90 USDT (+4.25%).
Notes
The calculation above excludes fees; including buy fees raises the effective average cost slightly.
Average cost only says where your cost sits. It is not advice to keep buying: averaging down lowers the cost but increases position size.
FAQ
Why is it below the simple average of the three prices?
Because the amounts differ: the 2,200 buy is the largest and acquired the most coins, pulling the weighted cost down. The weighted average here is 2,370.17 versus a simple average of 2,400 USDT.
Is the method the same for equal amounts?
Yes. Both use "amount ÷ price" per buy, summed into coins held, then divided into total invested. The only difference is that uneven amounts show a bigger weighting effect.