Reverse Average Entry Calculator
Find how many more coins to buy to reach a target average entry price, including cash needed, buy fees and a limited budget.
Your holdings and next buy
Required purchase
Next-buy price: 80 USDT / BTC — manual assumption.
- Additional coins needed
- 1 BTC
- Purchase cash
- 80 USDT
- Assumed buy fee
- 0 USDT
- Total cash including fee
- 80 USDT
- Resulting total quantity
- 2 BTC
- Target average before fees
- 90 USDT / coin
Fees are additional cash, excluded from the average entry. Outputs use up to 12 significant digits; tiny values may use scientific notation. Exchange lot sizes, minimum orders, slippage and stablecoin depegging are excluded.
How to solve a target average entry
Let Q be existing coins, A the current average, T the target and B the next-buy price. The new weighted average is (Q × A + x × B) ÷ (Q + x).
x = Q × (A − T) ÷ (T − B). Purchase cash = x × B. Fee = purchase cash × fee percent ÷ 100.
Substitution: 1 × (100 − 90) ÷ (90 − 80) = 1 additional BTC.
Worked example: 1 coin at 100, a target of 90 and a next-buy price of 80 require 1 × (100 − 90) ÷ (90 − 80) = 1 more coin. Purchase cash is 80 USDT, total quantity is 2 coins and the average is 90 before fees.
A changed target must be strictly between your average and next-buy price. Buying below the current average can lower it; buying above it can raise it. Buying at the target cannot reach it in a finite order unless your average already equals it.
With a limited budget, affordable coins = budget ÷ (1 + fee percent ÷ 100) ÷ B. The affordable average is shown separately and does not imply the target is reached.
Check a series of known fills with the forward average-entry calculator. This tool sizes a hypothetical purchase and does not place orders or store holdings.