When you add to a crypto position, the new average entry is total purchase cost divided by total coins acquired. Each buy is weighted by how many coins it added, so averaging two prices directly is only correct when both buys acquired the same coin quantity. Enter each purchase as its own row in the Average Cost Calculator to combine different dollar amounts or coin quantities.
Why the arithmetic is weighted
A simple average gives every price equal weight. A position's average cost gives each purchase weight according to its quantity. If one buy acquires 0.01 BTC and another acquires 0.03 BTC, the second buy has three times the effect on the average because it represents three times as many coins.
For buys entered as dollars, calculate each buy's coin quantity as:
coins acquired = dollars spent ÷ buy price
Then combine the rows:
average entry = total cost ÷ total coins acquired
This is the same weighted-average principle used for investment cost basis: total investment cost divided by the number of units held. The Investor.gov glossary entry on average cost describes the concept for securities. Here, the example applies the arithmetic to crypto quantities and excludes tax-lot accounting rules.
Worked example: a smaller buy at a lower price
Assume you first spend $600 on a coin at $60,000. That purchase adds:
$600 ÷ $60,000 per coin = 0.01 coin
Later, you spend $300 at $30,000 per coin. The second buy also adds 0.01 coin:
$300 ÷ $30,000 per coin = 0.01 coin
Together, the buys cost $900 and acquire 0.02 coin. The weighted average entry is:
$900 ÷ 0.02 coin = $45,000 per coin
The arithmetic mean of $60,000 and $30,000 also happens to be $45,000 here, but only because the coin quantities acquired were equal. The dollar amounts differed, yet each buy added 0.01 coin. If the second purchase had been $600 at $30,000, it would add 0.02 coin, and the average would instead be $40,000: ($600 + $600) ÷ (0.01 + 0.02).
With no purchase fees, this is exactly how the calculator combines USD-mode rows. It converts each dollar amount to coins using that row's price, adds costs and quantities, then divides total cost by total coins. You can add multiple buys; the tool supports up to 20 rows.
How to enter buys when amounts differ
Use a separate row for each purchase rather than combining prices or averaging the price column yourself. For each row, check whether your records show a dollar amount spent or a coin quantity bought. The calculator accepts both kinds of entry:
- USD mode: enter the dollars spent and the purchase price. The tool derives coins as amount divided by price.
- Coins mode: enter the number of coins bought and the purchase price. The tool derives cost as quantity multiplied by price.
For example, a record might show $250 spent at $25,000, while another receipt states that 0.006 coin was purchased at $40,000. The first row contributes 0.01 coin and $250; the second contributes 0.006 coin and $240. The combined average before fees is ($250 + $240) ÷ (0.01 + 0.006), or $30,625 per coin. This example illustrates why the mode must match the amount you have: interpreting 0.006 coins as $0.006, or treating $250 as coin quantity, changes the result completely.
Use the calculator to add the rows and inspect total cost, total coins, average entry, estimated break-even, and current P&L. For a position-size calculation based on a planned entry and stop, see the position size calculator. To estimate profit from a planned entry and exit, see the crypto profit calculator.
How the fee input changes the result
The average-cost tool applies its fee percentage by reducing the coins received for each buy. It leaves the entered purchase cost intact. For USD-mode buys, it calculates the pre-fee quantity from dollars divided by price, then multiplies that quantity by one minus the fee percentage. The average is total cost divided by this lower net coin amount.
For example, if a $100 buy at $10,000 has a 1% fee estimate, the pre-fee quantity is 0.01 coin and the calculator treats the received amount as 0.0099 coin. Its average for that single row is $100 ÷ 0.0099, or about $10,101.01 per coin. With two buys, it applies the entered rate to each row and sums the resulting net quantities.
The displayed break-even is then calculated as average entry divided by one minus the fee rate, which estimates the additional price needed to cover a sale fee at that same percentage. The current P&L calculation is net coins multiplied by the current price minus total purchase cost; it does not subtract a separate sale fee from that P&L figure. Treat the fee fields and outputs according to those definitions, and compare them with your own exchange statement if it includes other charges, discounts, or taxes.
Common mistakes
- Averaging prices without weights. Use total cost divided by total coins. The midpoint of two prices is valid only when both buys add the same quantity.
- Mixing dollars with coin quantity. Select USD mode for an amount spent and Coins mode for an amount of crypto. The purchase price is needed in either mode.
- Using the current price as a historical fill price. Enter the actual price for each purchase. A changed market quote does not rewrite the price paid on an earlier buy.
- Omitting a purchase or duplicating a row. The result is only as complete as the transactions entered. Reconcile rows against your own records before relying on the average.
- Assuming fee handling matches every exchange statement. This calculator uses a single percentage estimate and models it as fewer coins received. Actual fees can differ by order type, venue, discount, or other conditions.
- Treating average entry as a tax calculation. An average entry estimate is not a substitute for jurisdiction-specific cost-basis or tax-lot accounting.
FAQ
How do I average two crypto buys with different amounts?
Add their costs and divide by the combined coins acquired. If the amount is specified in dollars, first divide each spend by its own fill price to find the coins from that buy.
Should I average the two prices directly?
Only if each buy acquired the same coin quantity. Otherwise use the weighted calculation: total cost divided by total quantity.
Does adding a buy below my average always lower it?
If the additional buy acquires a positive quantity below the current average and the costs and quantities are measured consistently, the combined weighted average falls. A buy above the current average raises it.
Does the calculator include fees?
Yes, when you enter a fee percentage. It reduces the coins received on each buy and estimates a break-even price that includes a sale fee at the same percentage. Its current P&L output does not subtract a separate exit fee.
Can I use different amounts in each row?
Yes. Choose USD mode when the row is a dollar spend or Coins mode when it is a crypto quantity, and enter that buy's own price.
Not financial advice. This guide explains weighted-average arithmetic, not whether or how to trade.