Your crypto cost basis is the total amount you paid to acquire a coin, including any fees. It is the number you subtract from your sale proceeds to work out a capital gain or loss, so getting it right is the single most important step in crypto tax. When you’ve bought the same coin many times at different prices, the standard approach is a weighted average: add up the cost of every purchase (quantity × price plus fees) and divide by the total quantity you hold. Our average cost & cost-basis calculator does this for you. Everything here is general information, not tax advice.
What to include in cost basis
Cost basis is more than the headline price. Include:
- The amount you paid for the coins (quantity × price).
- Trading fees charged by the exchange.
- Network/gas fees paid to acquire the asset.
Do not include fees that relate to selling (those reduce your proceeds instead) or costs unrelated to the acquisition. Including acquisition fees is not just good record-keeping — it legitimately reduces your taxable gain.
The weighted-average formula
For multiple buys, cost basis per coin is:
average cost = Σ(quantity × price + fee) ÷ Σ quantity
Worked example
| Buy | Quantity | Price | Fee | Cost |
|---|---|---|---|---|
| 1 | 0.25 | $40,000 | $20 | $10,020 |
| 2 | 0.25 | $60,000 | $20 | $15,020 |
| Total | 0.50 | — | $40 | $25,040 |
Total cost basis is $25,040 for 0.5 coins, so your weighted-average cost is $25,040 ÷ 0.5 = $50,080 per coin. If you later sell 0.5 coins for $55,000, your gain is $55,000 − $25,040 = $29,960. Plug it into the profit calculator to confirm.
Cost-basis methods by country
Different tax authorities require or allow different methods, and the method changes your gain when you sell only part of a holding.
| Method | What it means | Used by |
|---|---|---|
| Average cost (pooling) | All units share one weighted-average cost | UK (Section 104 pool), Canada (ACB) |
| FIFO | First coins bought are first sold | US (default), allowed in many countries |
| Specific identification | You choose which lot you sold | US (with records), Australia (per parcel) |
- United Kingdom: HMRC requires share-pooling, so every unit of a given coin shares one average cost (with special same-day and 30-day rules).
- Canada: the CRA uses the adjusted cost base (ACB), a moving weighted average.
- United States: the IRS default is FIFO, but you may use specific identification if you can document which units you sold — often the most tax-efficient choice.
- Australia: the ATO tracks cost per parcel and lets you identify which parcel you disposed of.
Because the rules differ, the cost basis our calculator shows (a weighted average) matches the UK and Canadian approach directly and gives a solid baseline elsewhere. See how crypto capital gains tax works for how the gain is then taxed.
Cost basis for swaps, staking and airdrops
- Swaps: swapping coin A for coin B is a disposal of A. Coin B’s cost basis is its market value at the moment of the swap.
- Staking rewards: the value of a reward when you receive it is both income and the cost basis for that reward when you later sell it. See staking rewards and taxes.
- Airdrops and forks: usually take a cost basis equal to their market value when you gain control.
Keeping records
Good cost-basis tracking starts with good records. For every transaction, log the date, the coin, the quantity, the value in your local currency, and the fee. Exchanges’ CSV exports are a starting point, but they often miss on-chain transfers and DeFi activity. Consolidate everything before tax time — the average cost calculator is a quick way to turn a list of buys into the single figure you need.
How method choice changes your gain
When you sell only part of a holding, the cost-basis method you use directly changes the reported gain — and therefore your tax. Imagine you bought 1 coin at $10,000 and another at $30,000, then sold 1 coin for $40,000:
- FIFO sells the $10,000 coin first → gain of $30,000.
- Specific identification (selling the $30,000 coin) → gain of $10,000.
- Average cost uses a $20,000 basis → gain of $20,000.
Same sale, three very different taxable gains. Where your country allows a choice (notably the US), selling your highest-cost lots first via specific identification minimises the immediate gain — though it may leave a larger gain for later. Where pooling is mandatory (UK, Canada), you don’t get to choose; the average is applied automatically. This is why knowing your country’s method isn’t academic: it can change your tax bill by thousands on the same transaction.
Cost basis when you receive crypto for free
Not all crypto is bought. If you’re paid in crypto, mine it, or receive a reward, your cost basis is generally the market value when you received it — the same figure you reported as income. That prevents double taxation: you’ve already paid income tax on that value, so only the subsequent change in price is a capital gain. Gifts are a special case in some countries, where you may inherit the giver’s cost basis. Record the receipt value carefully, because without it a later sale looks like pure profit and you’ll overpay.
Common mistakes
The errors that most often inflate a tax bill are forgetting to include acquisition fees, mixing up buy and sell fees, and resetting cost basis to zero after a wallet transfer (transfers don’t change basis). We cover more in common crypto tax mistakes.
Calculate cost basis carefully and your gains — and your tax — will be accurate and defensible. When the situation is complex (lots of DeFi, multiple methods, large sums), get a qualified professional involved; these calculators provide estimates, not advice.