How the profit calculation works
A crypto trade has two sides, and most exchanges take a cut of both. When you buy, the fee is added to what you spend; when you sell, it is subtracted from what you receive. Your real profit is the gap between those two after-fee figures, not the gap between the two prices on the chart.
The fee is your exchange's trading fee as a decimal (0.5% = 0.005), applied once per side. If your platform charges different rates for buying and selling, or adds a spread on top, your real result will sit slightly below what the calculator shows, so treat the fee field as a minimum.
Worked examples
Breakeven is higher than you think
Because fees hit both sides, the price only needs to drift a little for a "flat" trade to lose money. The price at which you truly break even is:
At a 0.5% fee per side, a £20,000 buy breaks even at £20,201.01, roughly 1% higher. At 1% per side the gap doubles to about 2%. Frequent trading multiplies this cost: ten round trips at 0.5% per side means the market has to move about 10% in your favour before you make anything at all. Knowing your breakeven before you enter a trade is one of the simplest edges available, which is why the calculator shows it even before you type a sell price.
Tax and record keeping
UK tax does not wait for you to cash out to pounds. Swapping one coin for another, or spending crypto, each count as a disposal, and gains beyond the Capital Gains Tax annual exempt amount are taxable. HMRC expects a record of dates, amounts, values and fees for every trade, and exchange fees can usually be deducted from the gain, another reason to track them. The cryptoassets guidance on gov.uk covers the details.
Never enter your seed phrase or private keys into any website, including this one. A profit calculator only needs prices, and anything that asks for more is trying to rob you.
Crypto is highly volatile and largely unregulated in the UK, with no FSCS protection: be prepared to lose everything you put in. Figures here are guidance, not financial advice.
Frequently asked questions
Why is the breakeven price higher than my buy price?
Because fees are usually charged twice, once when you buy and once when you sell. To walk away with the money you put in, the sale has to cover the original cost plus both fees. With a 0.5% fee per side, a coin bought at £20,000 must reach about £20,201 before you are back to zero.
What fee percentage should I enter?
Use your exchange's trading fee for the market you traded, shown on its fees page or on each trade confirmation. Typical exchange fees run from about 0.1% to 1% per trade. If you were charged a flat amount instead, divide it by the trade value to turn it into a percentage.
Does this work for any coin or token?
Yes. The calculator never looks up prices and has no list of tickers, so it works for any cryptocurrency, or any fraction of one. Enter the prices you actually paid and received in pounds, along with the quantity you traded.
Do I owe tax on crypto profits in the UK?
Possibly. Selling crypto at a gain can trigger Capital Gains Tax once your total gains pass the annual exempt amount, and HMRC expects records of every disposal. This calculator ignores tax entirely, so check the cryptoassets guidance on gov.uk or ask an accountant.
Is anything I type sent anywhere?
No. Everything is calculated in your browser and nothing is uploaded or stored. Even so, never enter a seed phrase or private key into any website, including this one. A profit calculator only ever needs prices and quantities.