ACB Calculator

ACB Calculator

Updated Aug 9, 2026 By Jehan Wadia

#	Type	Date	Shares	Price / Share	Commission	Cost / Net Proceeds	ACB of Sold	Capital Gain / Loss	Shares Held	Running ACB	ACB / Share
Enter transactions above and click Calculate ACB.

Type

Date

Price / Share

Commission

Cost / Net Proceeds

ACB of Sold

Capital Gain / Loss

Shares Held

Running ACB

ACB / Share

Enter transactions above and click Calculate ACB.

Introduction

The Adjusted Cost Base (ACB) Calculator helps you track what your shares really cost you. ACB is the average price you paid for each share, plus any fees like commissions. You need this number to work out your capital gain or loss when you sell.

Just add each Buy or Sell you made. Type in the date, the number of shares, the price per share, and the commission. The calculator then shows your ACB per share, your total book value, and your realized gain or loss after every trade.

It uses the weighted average cost method, the same way the Canada Revenue Agency (CRA) expects. So when you buy more shares at a new price, your ACB per share updates right away. When you sell, the tool subtracts the ACB of those shares from your net proceeds to find your gain or loss. If you only need the average buy price without the tax side, the Stock Average Calculator is a quicker option, and the Stock Profit Calculator handles a single round-trip trade.

You also get a full table of every step and a chart that compares your ACB per share to the price you paid or got. This makes it easy to see your numbers, keep good records, and get ready for tax time.

How to use our ACB Calculator

Enter each time you bought or sold shares. The calculator works out your adjusted cost base (ACB), your ACB per share, and your capital gain or loss on every sale.

Type: Pick Buy if you bought shares, or Sell if you sold them.

Date: Type the date of the trade. This is optional, but it helps keep your records in order.

Shares: Enter how many shares you bought or sold in that trade. You can use partial shares.

Price / Share: Enter the price you paid or got for one share, before fees.

Commission: Enter the trading fee for that order. Leave it at 0 if there was no fee. Fees on a buy raise your ACB. Fees on a sell lower your proceeds.

Add Transaction: Click this to add another buy or sell row. Add your trades in the order they happened.

Calculate ACB: Click this to see your shares held, total ACB, ACB per share, and total realized gain or loss. A table and chart show how your ACB changes after each trade.

Remove and Reset: Click Remove to delete one trade row. Click Reset twice to clear everything and start again.

What Is Adjusted Cost Base (ACB)?

Adjusted cost base, or ACB, is the average cost you paid for the shares you own. In Canada, the Canada Revenue Agency (CRA) uses your ACB to work out your capital gain or loss when you sell an investment. Your ACB includes the price of the shares plus any fees, like broker commissions, that you paid to buy them.

How ACB Is Calculated

Canada uses the weighted average cost method. That means all shares of the same stock in the same account are pooled together. You do not track each buy on its own. Instead:

ACB per share = total book value ÷ total shares you hold (the same idea behind any Weighted Average Calculator)
When you buy: add the cost plus commission to your total ACB, and add the new shares to your share count. This changes your average cost.
When you sell: your ACB per share stays the same. You remove the sold shares' share of the ACB from your book value.

Working Out Capital Gain or Loss

When you sell, the math is simple:

Capital gain or loss = net proceeds − ACB of the shares sold

Net proceeds are the sale price times the number of shares, minus the selling commission. If the answer is positive, you have a capital gain. If it is negative, you have a capital loss. In Canada, you normally report 50% of a capital gain as taxable income. Capital losses can lower capital gains from the same year, past years, or future years. To estimate the tax owing on those gains, try the Capital Gains Calculator or the Capital Gains Tax Calculator, and check how the gain fits your bracket with the Taxable Income Calculator.

A Quick Example

You buy 100 shares at $25 with a $9.99 fee. Your ACB is $2,509.99, or about $25.10 per share. Later you buy 50 more shares at $30 with a $9.99 fee, adding $1,509.99. Now you hold 150 shares with a total ACB of $4,019.98, so your ACB per share is about $26.80. If you then sell 75 shares at $35 with a $9.99 fee, your net proceeds are $2,615.01 and the ACB of those shares is about $2,010. Your capital gain is roughly $605. To see what that trade returned in percentage terms, run the numbers through the ROI Calculator or the CAGR Calculator.

Things That Change Your ACB

Commissions and fees: buying fees raise your ACB. Selling fees lower your proceeds. Ongoing fund fees are separate, and the Expense Ratio Calculator shows their long-run drag.
Return of capital (ROC): some ETFs and trusts pay ROC, which lowers your ACB.
Reinvested distributions (DRIPs): reinvested amounts raise your ACB, even if you never saw the cash. The DRIP Calculator and Dividend Calculator help you total up those reinvested payouts.
Stock splits: the share count changes, so ACB per share changes, but total ACB stays the same.
Foreign stocks: convert both buys and sells to Canadian dollars using the exchange rate on each trade date. The USD to CAD Calculator and Currency Calculator make that step easier.

Rules Worth Knowing

The superficial loss rule blocks a capital loss if you (or your spouse, or a company you control) buy the same stock within 30 days before or after the sale and still hold it. The denied loss is added to your ACB instead.

You must also keep one ACB pool per stock across all your non-registered accounts, not one per account. ACB does not matter inside an RRSP, RRIF, TFSA, or FHSA, because gains in those accounts are not taxed as capital gains. Keep your trade records and slips, since brokers do not always report ACB correctly. The same pooling idea applies to coins and tokens, which the Crypto Tax Calculator and Crypto Profit Calculator cover, and you can project the growth of what you keep invested with the Investment Calculator.

Formulas used

Cost of a Buy Transaction

\text{Cost} = \text{Shares} \times \text{Price} + \text{Commission}

Running ACB After a Buy

\text{ACB}_{\text{new}} = \text{ACB}_{\text{prev}} + (\text{Shares} \times \text{Price} + \text{Commission})

ACB per Share (Weighted Average Cost)

\text{ACB per Share} = \frac{\text{Total ACB}}{\text{Shares Held}}

ACB of Shares Sold

\text{ACB}_{\text{sold}} = \frac{\text{ACB}_{\text{prev}}}{\text{Shares}_{\text{prev}}} \times \text{Shares}_{\text{sold}}

Net Proceeds of a Sell Transaction

\text{Net Proceeds} = \text{Shares}_{\text{sold}} \times \text{Price} - \text{Commission}

Capital Gain / Loss on a Sale

\text{Gain} = \text{Net Proceeds} - \text{ACB}_{\text{sold}}

Running ACB and Share Balance After a Sell

\text{ACB}_{\text{new}} = \text{ACB}_{\text{prev}} - \text{ACB}_{\text{sold}}, \quad \text{Shares}_{\text{new}} = \text{Shares}_{\text{prev}} - \text{Shares}_{\text{sold}}

Total Realized Gain / Loss

\text{Total Gain} = \sum_{i \in \text{sells}} \left( \text{Net Proceeds}_i - \text{ACB}_{\text{sold},i} \right)

Frequently asked questions

Does the order I enter my trades in matter?

Yes. Add your trades in the order they happened, oldest first. The calculator works down the list one row at a time. If a sell comes before the buy that gave you those shares, the math will be wrong or you will see an error.

Why do I get an error saying I cannot sell that many shares?

You tried to sell more shares than you held at that point in the list. Check three things:

Did you enter all your earlier buys?
Are your trades in date order?
Did you type the share count correctly?

Can I use this calculator for more than one stock at a time?

No. Use one calculation per stock. ACB is pooled by each individual security, so mixing two stocks in one list would give you a meaningless average. Run the calculator again for your next stock.

Do I have to fill in the date?

No, the date is optional. The calculator uses the row order, not the date, to do the math. Still, adding dates makes your table easier to read and helps with your tax records.

What if I leave the commission blank?

It is treated as $0. If your broker charges no fee, that is fine. If you did pay a fee, enter it, or your ACB and your gain will both be off.

Can I enter fractional shares?

Yes. The share field accepts decimals, so you can enter amounts like 12.345 shares. This helps with DRIPs and apps that sell partial shares.

Why does my ACB per share drop to $0.00 after I sell everything?

Because you own nothing. When your share count hits zero, your total ACB is zero too, so there is no cost per share left. Your realized gain or loss stays in the summary.

How do I enter a return of capital (ROC) payment?

ROC lowers your ACB but does not change your share count, so there is no direct field for it. A workaround is to reduce the price on an earlier buy row so your total ACB drops by the ROC amount. Keep a note of what you did for your records.

How do I handle a stock split?

Splits do not change your total ACB, only your share count. Adjust the shares and price on your earlier buy rows to the post split numbers. For a 2 for 1 split, double the shares and halve the price on each buy.

Does this calculator work out my tax bill?

No. It gives you the capital gain or loss. In Canada you then report the taxable part of that gain on your return. Use a capital gains tax calculator to estimate the tax owing.

Is the realized gain shown before or after tax?

Before tax. It is your full capital gain or loss from all sells added together, after commissions. No inclusion rate or tax rate is applied.

What does the chart show me?

The solid line is your ACB per share after each trade. The dashed line is the price of that trade. When the price line sits above the ACB line, you are buying or selling above your average cost.

Why did my ACB per share go up after I bought more shares?

Because you paid more than your old average. New buys are blended into the pool, so a higher price pulls the average up and a lower price pulls it down. Selling never changes your ACB per share.

Does a sell change my ACB per share?

No. A sell removes shares and removes their share of the book value at the same average cost. Your cost per share stays where it was until your next buy.

Should I include shares held in my TFSA or RRSP?

No. Gains in registered accounts are not taxed as capital gains, so ACB does not matter there. Only track your non registered, taxable holdings.

I hold the same stock at two brokers. Do I combine them?

Yes. The CRA wants one ACB pool per stock across all your non registered accounts. Enter every buy and sell from both brokers into one list, in date order.

How do I enter US stocks?

Convert each trade to Canadian dollars first, using the exchange rate on that trade date. Then enter the Canadian dollar price and commission. Do not mix currencies in one list.

Are my numbers saved if I close the page?

No. Nothing is stored or sent anywhere. Close or refresh the page and your entries are gone, so copy your table or take a screenshot before you leave.

Why do I have to click Reset twice?

It is a safety step so you do not wipe out your trades by accident. The first click asks you to confirm. Click again within five seconds to clear everything.

Can I enter reinvested dividends from a DRIP?

Yes. Treat each reinvestment as a Buy row. Enter the number of shares bought and the price per share, with $0 commission. This raises your total ACB, which is correct.

Does this handle the superficial loss rule?

No. The calculator shows the raw loss. If you rebought the same stock within 30 days before or after the sale, that loss may be denied and added to your ACB instead. Check that rule yourself.

Why is my gain slightly different from my broker's number?

Brokers often track ACB per account, not across all your accounts. They may also miss ROC, DRIPs, or foreign exchange. Your own pooled record is usually the more accurate one for tax.

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