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Average cost calculator: what did you really pay per unit?

Enter up to six purchases and the fee you pay on each. The calculator shows how many units you own and the average price you paid for them, which is rarely the average of the prices.

By the Bitfolio Explainer Desk · Checked against primary sources · 5 min read

Education only, not investment, tax or legal advice. Crypto-assets are high-risk — risk disclosure.

A pink piggy bank standing on scattered US dollar bills — Photo: “Piggy-Bank version 2” by cafecredit, CC BY 2.0, via flickr.com · Edited: duotone, cropped.

The short answer

Your average cost is the total you spent divided by the units you received. Four $100 buys at $50, $40, $25 and $40 with a 0.5% fee get 10.945 units, an average cost of $36.55, below the $38.75 average of the four prices.

Key takeaways

Average cost per unit = total spent ÷ total units received, fees included.
Equal dollar amounts buy more units when the price is low, so the average cost usually lands below the plain average of the prices.
Your average cost is the price the asset must reach, before selling costs, for the whole position to break even.
Spreading purchases out does not prevent losses and can trail a single lump-sum purchase when prices rise.

How do you use the average cost calculator?

Three steps

1
Enter each purchase
For each buy, type the dollars you spent (including the fee) and the price per unit at the time. Leave unused rows empty.
2
Set the fee
Enter the percentage fee taken from each purchase. Use 0 if fees were charged separately and already added to the amount spent.
3
Read the result
You get total spent, units acquired, your average cost per unit and, for comparison, the simple average of the prices you entered.

It suits a regular buying plan, which Investor.gov describes as investing equal portions at regular intervals regardless of market ups and downs¹, but any set of purchases of one asset works.

What formula does the calculator use?

Units from each buy = amount spent × (1 − fee) ÷ price. The fee comes out of the money first; the rest buys units.
Total units = sum of the units from every buy.
Average cost per unit = total spent ÷ total units.
Simple average of prices = sum of the prices ÷ number of buys (shown only for comparison).

The average cost is a weighted average: each price counts in proportion to the units it bought. Because a fixed dollar amount buys more units at a low price, low prices carry more weight. Fees are included, which matches how the IRS describes cost basis for crypto: the amount spent to acquire it, including fees and commissions³.

Worked example: four $100 buys at different prices

Worked example

$400 spread over four purchases (illustrative)

You spend $100 each time at prices of $50, $40, $25 and $40, with a 0.5% fee per purchase.

You receive 10.945000 units for $400.00, so your average cost is $400 ÷ 10.945 = $36.55 per unit. The simple average of the four prices is $38.75. Without the fee, the average cost would be $36.36.

Purchase by purchase; a $0.50 fee comes out of each $100 (illustrative, calculator formula)

Buy	Spent	Price	Units
1	$100.00	$50.00	1.9900
2	$100.00	$40.00	2.4875
3	$100.00	$25.00	3.9800
4	$100.00	$40.00	2.4875
Total	$400.00	—	10.9450

The $25 purchase alone supplies 36% of the units, which pulls the average down. At the last price of $40 the holding is worth $437.80, above the $400 paid. To break even before any selling fee, the price only needs to be back at $36.55, not at the first price of $50.

Is spreading out purchases better than buying all at once?

Not reliably. It depends on the path prices take. The same $400 with the same 0.5% fee gives different winners on two made-up price paths:

Units bought with $400: four $100 buys vs one lump sum at the first price (illustrative)

Price path	Spread out	All at once	More units
Falls, then recovers: $50 → $40 → $25 → $40	10.9450	7.9600	Spreading out
Rises steadily: $25 → $40 → $50 → $60	10.1158	15.9200	All at once

Figure · Two ways to invest the same money

Spreading out (DCA)

Buys more units when cheap
Softens short-term price swings
Cash waiting may earn little
Pays a fee on every purchase

Lump sum

Fully invested from day one
Often ahead when prices rise
Exposed to a bad entry point
Fewer transaction fees

Source: [2]

FINRA notes that holding cash longer and investing gradually lowers risk but often produces lower returns than a lump sum, especially over longer periods, and that per-trade fees can make it more expensive².

What does the calculator leave out?

Selling costs and profit. It reports cost, not gain. Use our profit and loss calculator to add a sale price and sell fee.
Spreads and slippage. The price you enter should be the price you actually got. See liquidity and slippage.
Tax-lot rules. Tax authorities may not use an average. For crypto in the U.S., the IRS treats units as sold first in, first out unless you specifically identify which units you sold³.
Flat fees. The fee field is a percentage. A fixed $1 charge on a $100 buy is 1%; convert before entering it.
Opportunity cost. Money waiting for later purchases may sit in cash.

Risk warning

Averaging does not protect against losses

If the price keeps falling, every purchase is worth less than you paid, however smooth your average looks. Crypto-assets can fall sharply and stay down. Only invest money you can afford to lose.

What mistakes do people make when averaging down?

Common beginner mistakes

Averaging the prices
The simple average ($38.75 here) overstates your cost when you bought fixed dollar amounts.
Leaving fees out
Fees raise your true cost per unit and your break-even price.
Treating a lower average as a gain
A lower average cost only matters if the price later rises above it.
Mixing different assets
Average cost works for one asset at a time. Combining two coins in one calculation gives a meaningless number.

Frequently asked questions

Is average cost the same as cost basis?

They are related but not identical. Cost basis is assigned per unit or lot for tax purposes, and U.S. crypto rules use first in, first out unless you identify specific units³. Our U.S. crypto tax basics explains more.

How often should purchases be made?

The calculator does not care about timing, only amounts and prices. What matters is a schedule you can keep, such as each payday.

Why is my exchange's average price different?

Platforms may exclude fees, count fees paid in another token or include transfers. Check what your platform's figure includes.

Can I include sales in the calculation?

No. It handles purchases only. After a sale, the remaining units' cost depends on which units your tax rules treat as sold.

The bottom line

Your average cost is total spent divided by units received, and it is usually lower than the average of the prices when you buy fixed dollar amounts. It tells you your break-even price, not whether the plan was wise: averaging smooths the entry price but cannot stop losses, and FINRA notes a lump sum often does better when prices rise².

Sources

Dollar Cost Averaging (glossary) — Investor.gov, U.S. Securities and Exchange Commission Primary source
Dollar-Cost Averaging — FINRA, 2026 Primary source
Frequently Asked Questions on Virtual Currency Transactions — Internal Revenue Service (IRS), 2026 Primary source

How we checked this page: every figure above links to the numbered source it came from. Spotted an error? Tell the desk — see our editorial policy.