ACB calculator
ACB calculator: enter every buy and sale of one stock, fund or coin with its commission, and the calculator pools the buys into a single adjusted cost base, draws each sale out of the pool at its average cost, and works out the gain and the federal tax on it. 50% of the gain is taxable income.
The adjusted cost base is the average of everything you paid for the identical property you hold. It exists because Canada does not let you choose which shares you sold. You sold the average.
Transactions in one stock, fund or coin
- Units held
- 250
- Adjusted cost base
- $13,750
- ACB per unit
- $55
- Total capital gain
- $3,750
- Taxable capital gain
- $1,875
- Federal tax on the gain
- $384
| Date | Transaction | Quantity | Proceeds | ACB of units sold | Gain or loss | Units held | ACB | ACB per unit |
|---|---|---|---|---|---|---|---|---|
| January 15, 2026 | Buy | 100 | 100 | $4,000 | $40 | |||
| March 2, 2026 | Buy | 200 | 300 | $15,000 | $50 | |||
| May 20, 2026 | Buy | 100 | 400 | $22,000 | $55 | |||
| September 10, 2026 | Sell | 150 | $12,000 | $8,250 | $3,750 | 250 | $13,750 | $55 |
The rest of your year's sales
The ACB calculator above prices the buys and sales of one security. The calculator below is for the rest of the return: add sales of other shares, property and crypto, or import a broker or exchange file and it pools the buys at average cost for you, then totals the year.
The pool
What the adjusted cost base is
The adjusted cost base of an asset is what all of it cost you: the purchase prices plus the costs of buying, added together across every purchase. Buy the same property again and the new cost joins the old pool and the average moves. Nothing resets.
Each identical property keeps its own pool. Shares of one company pool separately from shares of another, and each cryptocurrency pools on its own, so enter one security at a time. A buying commission joins the pool's cost; a selling commission comes off the proceeds instead.
Canada has no holding-period concession, so which buy a sale traces back to never changes the tax. Every unit in the pool costs the same average.
How a sale works
Every sale draws the average
Each sell consumes the pool at its average unit cost. The gain is the proceeds minus the average cost of the units sold, never the price of a lot you picked. Sell 150 of 400 shares and the cost side of the gain is 150 times the average.
The pool that remains keeps the same average. Its quantity falls and its total cost falls with it, so the next sale measures against the same base until another buy moves it. In the example below, 250 shares remain at $13,750 after the sale, still the same per-share figure.
Worked example
Three buys, one sale: $55 a share
The calculator above opens on this example, so you can change any transaction and watch the pool move. You buy 100 shares for $4,000 on January 15, 2026, 200 more for $11,000 on March 2, 2026, and 100 more for $7,000 on May 20, 2026. The pool holds 400 shares at a total cost of $22,000, an average of $55 a share.
On September 10, 2026 you sell 150 shares for $12,000. The sale draws 150 times $55 of cost from the pool, $8,250, so the gain is $12,000 minus $8,250: $3,750. 50% of it, $1,875, lands in your income, and the federal tax on it at $85,000 of other income is $384.
One partial sale from a pooled position in the 2026 return
| Step | Amount |
|---|---|
| Buy 100 + 200 + 100 shares | $22,000 |
| Pool: 400 shares | $55 a share |
| Sell 150 shares, proceeds | $12,000 |
| Average cost of the shares sold | $8,250 |
| Capital gain | $3,750 |
| Taxable half at the 50% inclusion rate | $1,875 |
| Federal tax on the gain at $85,000 income | $384 |
Common mistakes
Mistakes that change the number
- Picking a lot. You cannot sell the cheap shares and keep the expensive ones. The average decides, and a broker statement that shows lots is bookkeeping, not a tax election.
- Leaving fees out. Buying fees belong in the pool and selling fees come off the proceeds before the gain. Both ends move the number.
- Mixing pools. Shares of two companies are two pools, and each coin pools alone. Averaging across different assets understates or overstates every sale.
- Resetting the average after a sale. A sale drains quantity, not the per-share base. The remaining shares carry the same average into the next sale.
- Buying the same property within 30 days before or after a loss. The superficial loss rule denies the loss when the same property is acquired in that window and still held at the end of the 30th day after the sale, and the denied amount adds to the cost base of the new purchase. The calculator warns on the sale; it never adjusts the loss for you.
Questions
Frequently asked questions
What is the adjusted cost base?
The total cost of every unit of one identical property you hold, purchase prices plus buying costs, averaged across the units. Sell some and the gain measures against that average, not against any single purchase.
Can I choose which shares I sold?
No. Identical property pools at average cost, so every unit costs the same. The acquisition date attached to a sale is reporting detail; it never changes the tax, because Canada has no holding-period discount.
Do trading fees change my ACB?
Buying fees join the pool's total cost, which lifts the average. Selling fees do not touch the base; they reduce the proceeds of the sale instead.
What happens to the pool after a partial sale?
The quantity falls and the total cost falls in step, so the average stands still. In the worked example, 250 shares remain at $13,750, the same $55 a share.
What is the superficial loss rule?
Sell at a loss, buy the same property within 30 days before or after the sale, and still hold it at the end of the 30th day after the sale, and the loss is denied. The denied amount moves into the cost base of the property you bought. The calculator warns on the sale and leaves the adjustment to you.
Does the same averaging apply to crypto?
Yes. Each coin pools the same way, at average cost. Enter one coin's buys and sells in the calculator above, and every sale draws on the pool. The crypto calculator page works that side of it through.
Sources
Where these figures come from
Also on capitalgainstax.net