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Capital Gains Tax Calculator
Gain, allowance and rate by holding period.
What it does. Capital gains tax applies to the profit, not the sale price. The gain is proceeds minus what you paid minus allowable costs; an annual exempt amount is deducted from that, and the rate usually depends on how long you held the asset and what kind of asset it is.
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How to use Capital Gains Tax Calculator
- Enter the purchase and sale figures, plus buying and selling costs.
- Set the allowance and rate, or use a preset.
- Read the gain, the taxable gain and the estimated tax.
Allowable costs reduce the gain
The gain is not simply sale price minus purchase price. Costs of acquiring and disposing of the asset generally reduce it — broker fees, legal fees, survey costs, stamp duty on purchase, and for property the cost of capital improvements.
Repairs and maintenance usually do not count; improvements that add something new usually do.
This distinction matters most on property, where a new extension is capital and a replacement boiler generally is not. Keeping the paperwork for improvements over decades of ownership is what makes the deduction claimable at all.
Holding period usually changes the rate
| Holding | Typical treatment |
|---|---|
| Under a year | Often taxed as ordinary income (US short-term) |
| Over a year | Usually a lower long-term rate (US) |
| Any period | UK uses your income tax band, not the holding period |
| Main home | Frequently exempt or heavily relieved |
| Within a tax wrapper | ISA, 401(k), pension — usually no CGT at all |
The wrapper row is the one worth acting on in advance. Gains inside a tax-advantaged account are typically outside CGT entirely, so where an asset is held often matters more than when it is sold.
Losses and timing
Capital losses generally offset capital gains, and unused losses can often be carried forward. Realising a loss in the same year as a gain is a common and legitimate way to reduce a bill.
Rules against immediately repurchasing the same asset exist in most systems — the US wash sale rule and the UK bed-and-breakfasting rules — and they have different windows.
The annual exempt amount usually cannot be carried forward, so it is use-it-or-lose-it. Spreading a large disposal across two tax years is another common approach, though it depends on the asset being divisible.
Frequently asked questions
How is capital gains tax calculated?
On the profit, not the sale price: proceeds minus purchase price minus allowable costs. An annual exempt amount is deducted from the gain, and the remainder is taxed at the applicable rate.
What costs can I deduct from a capital gain?
Generally the costs of acquiring and disposing of the asset — broker and legal fees, stamp duty on purchase — and for property, capital improvements. Repairs and maintenance usually do not qualify.
Does how long I held the asset matter?
In the US, yes — assets held over a year usually get a lower long-term rate. In the UK the rate follows your income tax band rather than the holding period.
Can capital losses reduce my tax?
Generally yes: losses offset gains, and unused losses can often be carried forward. Watch the rules on repurchasing the same asset, which differ between systems.
Do I pay CGT on my main home?
In most systems a main residence is exempt or heavily relieved, though conditions apply if you let it out or used part of it for business. This tool estimates the gain; whether relief applies is a separate question.