Hundred SummersBuy-to-let calculator: yield, profit after tax, and the return on the money tied up
Gross and net yield, the cash left after interest, then the tax as HMRC actually charges it (interest not deductible, a 20% credit instead, the 2027 surcharge, additional-property stamp duty on the way in) for the return on equity a landlord really earns. Your figures never leave your browser.
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Worked example
Computed when this page was built by the same engine that runs the calculator above, so the figures below and the live tool can never disagree. Change any input above to see your own.
| Inputs | |
|---|---|
| Price / deposit | £250,000 / £62,500 |
| Mortgage rate (interest-only) | 5.5% |
| Rent | £1,250 a month, 2 empty weeks |
| Agent / other costs | 10% / £2,000 a year |
| Landlord's other income | £50,000 |
| Where | England |
| Results | |
|---|---|
| Gross yield / net yield | 6.0% / 4.4% |
| Additional-property stamp duty | £15,000 |
| Cash before tax (after interest) | £668 |
| Tax with the 20% interest credit (2027 rules) | £2,495 |
| Cash profit after tax | £-1,827 |
| Cash return on equity tied up | -2.3% |
The next question
What tax would I pay when I sell? →Property capital gains tax calculator
Or answer it with everything else: the full Hundred Summers plan connects your pay, pensions, savings, property, tax and spending year by year, and stress-tests them across 500 simulated market histories.
Read the guide
- Buy-to-let in 2026: the tax, the surcharge, and the sale →Section 24 explained with real numbers, why a higher-rate landlord can lose money on a property that makes a cash profit, plus the additional-property stamp duty, the April 2027 surcharge, and capital gains tax when you sell.
Why the headline yield misleads
Gross yield ignores everything that makes letting a business: empty weeks, agents, insurance, repairs, the mortgage, and above all the tax. Since April 2020 finance costs are not deductible. Tax is charged on rent less running costs at your marginal rate, then a 20% credit on the interest is allowed, capped at the tax on the property profit. For a basic-rate landlord that nets to the old position; for a higher-rate landlord it means 40% tax on money the lender received. From April 2027 property income pays a further two points. The calculator shows the full chain from rent to cash after tax, and states the return on the equity actually committed: deposit, additional-property stamp duty and fees.
What it does not count
Your own time, furnishing and licensing, energy-efficiency works, rent arrears, the cost of a bad tenant, and the capital gains tax on the way out, which the property CGT calculator prices. Capital growth is your assumption, shown separately from the cash return so the two can be judged apart. Owning through a company changes the tax entirely and is not modelled here. The rental income tax calculator gives the tax line alone; in the Hundred Summers app a rental property runs through every projected year with its income, costs, mortgage and eventual sale.
Sources
- HMRC, Tax relief for residential landlords: how it’s worked out (the basic-rate credit).
- HMRC, Renting out your property: paying tax.
- Stamp duty for additional properties: SDLT, LBTT ADS, LTT. Property income rates from April 2027: HM Treasury, Autumn Budget 2025.