Capital Gains Tax Calculator
The Capital Gains Tax Calculator estimates how much tax you owe when you sell a capital asset - shares, property, cryptocurrency, or collectibles. It covers US federal capital gains tax rates (0%, 15%, and 20% long-term; ordinary income rates short-term) and UK Capital Gains Tax rates with the current £3,000 annual exempt amount.
Educational estimate. Calculator results are for planning and information only, not financial, tax, medical, legal, or engineering advice. Verify important decisions with official sources or a qualified professional.
Capital Gains Tax Calculator
US & UK Capital Gains Tax Estimator
📐 Formula & Method
Capital Gain
Your taxable capital gain is the proceeds from the sale minus your cost basis (purchase price) and any allowable selling costs.
US Long-Term Capital Gains Tax (2026)
For assets held over 1 year. Thresholds shown are 2026 single-filer federal brackets. Net Investment Income Tax (NIIT) of 3.8% may apply for high earners.
UK Capital Gains Tax
UK CGT rates are 10%/20% for most chargeable assets and 18%/24% for residential property. The annual exempt amount remains £3,000 for individuals and personal representatives in 2026-27.
📋 How to Use
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1
Enter the purchase price (cost basis) — the original price you paid including buying costs.
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Enter the sale price — what you received when you sold the asset.
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3
Enter any selling costs such as commissions, legal fees, or broker charges.
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4
Select your holding period and tax situation (US or UK).
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5
For US rates, select your income band to determine your applicable capital gains rate.
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Click Calculate to see your capital gain, estimated tax, and net proceeds.
💡 Key Insights
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In the US, holding an asset over 12 months drops your tax rate from ordinary income (up to 37%) to long-term CGT (0/15/20%) — usually a >15-point saving.
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The US 0% long-term CGT bracket extends to $49,450 single / $98,900 joint of taxable income for 2026. Many early retirees realise gains tax-free here.
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The UK CGT annual exemption is £3,000 in 2026-27. The lower allowance makes ISA wrapping more valuable than ever.
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UK property CGT rates (18%/24%) are higher than non-property (10%/20%) and have no private residence relief unless it's your only home.
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Tax-loss harvesting lets US investors offset gains with realised losses — up to $3,000/year of ordinary income, with the excess carried forward.
🧮 Worked Examples
US long-term, mid bracket
Bought stock at $20,000, sold at $50,000, selling costs $1,000, single filer in 15% LT bracket.
UK higher-rate non-property
UK higher-rate taxpayer sells shares with £18,000 gain.
📊 How to Interpret Your Result
Gain offset by losses
No tax owed. Excess loss can offset other gains or up to $3,000 ordinary income (US).
Long-term US, 0% bracket
Realise as much gain as possible here — it's genuinely tax-free.
Short-term US gain
Taxed as ordinary income — up to 37% federally. Strongly consider waiting until 12 months to qualify for long-term rates.
UK higher-rate gain
Use Bed & ISA to shelter future gains. Spouses can split assets to use both annual exemptions.
⚠️ Common Mistakes to Avoid
Forgetting selling costs (brokerage fees, agent commissions).
Fix: These reduce your taxable gain dollar-for-dollar. Always include.
Mis-identifying holding period (US short vs long).
Fix: Long-term = held more than 365 days. Count from trade date, not settlement date.
Ignoring the US 3.8% NIIT.
Fix: Single filers above $200k MAGI / joint above $250k pay an extra 3.8% on investment income.
UK — forgetting the bed-and-breakfast 30-day rule.
Fix: You can't repurchase the same asset within 30 days to crystallise a loss; HMRC matches the disposal to the repurchase.
🎯 Who This Calculator Is For
Equity investors rebalancing
Plan disposals to stay within favourable brackets.
Property investors
Compute SDLT-adjusted gain on a UK second home or US rental.
Crypto / RSU sellers
Model the tax bite before liquidating large positions.
How Capital Gains Tax Works in the US and UK
A capital gain occurs when you sell a capital asset — stocks, bonds, real estate, cryptocurrency, or collectibles — for more than you paid for it. The profit (gain) is typically subject to capital gains tax. Losses can often be used to offset gains, reducing your tax bill.
In the United States, long-term capital gains (assets held more than 1 year) are taxed at preferential rates of 0%, 15%, or 20% depending on your taxable income. Short-term gains (held 1 year or less) are taxed as ordinary income — at rates from 10% to 37%. High earners may also owe a 3.8% Net Investment Income Tax (NIIT) on investment income above $200,000 (single) / $250,000 (married filing jointly).
In the United Kingdom, basic rate taxpayers pay 10% on most chargeable gains and 18% on residential property gains. Higher and additional rate taxpayers pay 20% on most chargeable gains and 24% on residential property gains. The annual exempt amount is £3,000 for individuals and personal representatives in 2026-27.
UK residents benefit from an annual CGT-free allowance. This means you can realise gains up to the annual exempt amount each tax year before paying any CGT. Principal Private Residence (PPR) relief means you usually do not pay CGT on gains from your main home.
🔬 Methodology & Accuracy
Formula: Gain = Sale price - Cost basis - Selling costs. Tax is applied at the appropriate rate band (US long-term 0/15/20%, short-term ordinary income; UK 10/20% non-property, 18/24% property; UK £3,000 annual exemption auto-applied).
Data sources: IRS Topic No. 409 capital gains and losses: https://www.irs.gov/taxtopics/tc409; IRS Publication 550: https://www.irs.gov/publications/p550; GOV.UK Capital Gains Tax rates and allowances: https://www.gov.uk/government/publications/budget-2025-overview-of-tax-legislation-and-rates-ootlar/annex-a-rates-and-allowances; HMRC Capital Gains Tax: https://www.gov.uk/capital-gains-tax
Last reviewed: January 2026 · General formula used: Capital Gain · Accuracy: Results are precise to two decimal places using IEEE-754 double-precision arithmetic. Intended for educational and planning use only.
For informational purposes only. Results are estimates based on the inputs and formulas provided. For financial, tax, medical, or legal decisions, consult a qualified professional. Rates and regulations change — always verify current figures with official sources.
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❓ Frequently Asked Questions
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