UK Buy-to-Let Mortgage Calculator
Five calculators in one place: what you can borrow, what it costs, what it yields, what the tax bill looks like and whether the deal actually works. Built on the PRA’s SS13/16 stress-testing rules and 2025/26 tax rates.
- PRA compliant
- Section 24 ready
- 2025/26 tax rates
- Current BoE base rate
- 3.75%
- Bank of England · December 2025
- Avg 5yr BTL rate (75% LTV)
- 5.54%
- Which? / UK lenders · December 2025
01
Affordability calculator
How much a lender will advance against your rent, using PRA-compliant stress testing and the interest coverage ratio for your tax position and property type.
Not sure what it would rent for?
Typical rents for the area, so you have a defensible figure to start from.
- Lower quartile
- £795
- Median
- £995
- Upper quartile
- £1,250
Region: North West · Source: ONS Private Rental Market Statistics, 2024-10
Five-year fixes are stress-tested at the pay rate, so they usually lend more. Anything shorter is tested at the pay rate plus 2%, or a 5.5% floor.
Maximum loan
£259,928
- Interest coverage ratio
- 125%
- Stress rate applied
- 5.54%
- Annual rental income
- £18,000
- Rent the lender needs to see
- £22,500
Lenders test that your rent covers 125% of the mortgage interest at a stressed rate of 5.54%, not the rate you actually pay. Five-year fixes may be tested at the pay rate, which is why they usually lend more.
02
Monthly payment calculator
What the mortgage costs each month on interest-only versus capital repayment, including the arrangement fee and the full cost of borrowing over the term.
Interest only
£928/mo
- Total interest
- £278,384
- Balance at the end
- £200,999
Capital & interest
£1,239/mo
- Total interest
- £170,736
- Balance at the end
- £0
- Total amount repaid
- £371,735
Interest only costs £311 less a month, but leaves the full £200,999 outstanding.
03
Rental yield calculator
Gross and net yield once mortgage, management, insurance, maintenance and void periods are taken off the rent.
Annual costs, for the net yield
5.76%
Gross yield
Before any costs
0.50%
Net yield
After every cost above
Yield rating
- Poorunder 4%
- Average - where this one sits4-6%
- Good6-8%
- Excellent8% and up
- Annual rental income
- £14,400
- Total annual costs
- £13,154
- Net annual profit
- £1,246
- Monthly cashflow
- £104
Gross yield is rent over price and ignores every cost. Net yield is what actually reaches you, so it is the number worth comparing between properties.
04
Stamp duty calculator
SDLT, LBTT and LTT band by band, with the additional-property and non-resident surcharges applied where they are due.
Stamp Duty Land Tax
£15,000
Effective rate
6.00%
| Band | Rate | Tax |
|---|---|---|
| £0 - £125,000 | 5% | £6,250 |
| £125,000 - £250,000 | 7% | £8,750 |
- Of which, additional-property surcharge
- £12,500
Rates are 2025/26. Scotland charges its Additional Dwelling Supplement on the whole price rather than band by band, and the 2% non-resident surcharge applies in England and Northern Ireland only.
80+
UK lenders, one application
Whole-of-market buy-to-let products, priced against the figures you have just worked out.
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Stop searching endlessly. Our matching engine finds the buy-to-let deals that fit your exact circumstances.
- Limited company and individual options
- HMO and portfolio landlord specialists
- Expert advice included
05
Full investment analysis
Total cash required, monthly cashflow, cash-on-cash return and what Section 24 costs you against the pre-2020 rules.
Cash needed
£79,500
Cash-on-cash return
-1.10%
Marginal investment
Negative monthly cashflow. It may still work for capital growth, but keep reserves to cover the shortfall.
What you put in
- Deposit (25%)
- £62,500
- Stamp duty
- £15,000
- Legal fees
- £1,500
- Survey & valuation
- £500
- Total capital required
- £79,500
What it returns each month
- Rent
- + £1,200
- Mortgage interest
- - £866
- Management
- - £120
- Maintenance
- - £208
- Insurance
- - £29
- Voids
- - £50
- Net monthly cashflow
- -£73
Section 24 impact
- Tax under the pre-2020 rules
- £0
- Tax under Section 24
- £1,727
- Extra tax Section 24 costs you
- £1,727
Since 2020 landlords can no longer deduct mortgage interest from rental profit. You are taxed on the profit before interest and given a 20% credit instead, which is why higher-rate landlords often hold property through a company.
Key regulatory changes for landlords
The rules behind these numbers are moving. What is already in force, and what is coming.
Renters’ Rights Act 2025
- Section 21 no-fault evictions abolished
- All tenancies now periodic (rolling) by default
- Rent increases limited to once per year
- Property Portal registration mandatory from April 2026
- Decent Homes Standard now applies to private rentals
Making Tax Digital for income tax
- Landlords with £50k+ rental income: quarterly digital reporting from April 2026
- Landlords with £30k–£50k: from April 2027
New property income tax rates
- Basic rate: 22% (was 20%)
- Higher rate: 42% (was 40%)
- Additional rate: 47% (was 45%)
Stamp duty and CGT changes (Oct 2024 / Apr 2025)
- Additional property surcharge: 5% (was 3%)
- SDLT threshold: £125,000 (was £250,000)
- CGT on property: 18% / 24% (was 10% / 20%)
How buy-to-let lending is assessed
A buy-to-let mortgage is underwritten against the property, not your salary. The lender takes the rent the property should achieve, applies a stressed interest rate that is usually higher than the one you will pay, and checks the rent still covers that interest by a set margin. That margin is the interest coverage ratio.
Two things move the answer more than anything else. The first is your tax position: a basic-rate taxpayer or a limited company is tested at 125% cover, a higher-rate taxpayer at 145%, which cuts the loan by around a seventh on identical rent. The second is the length of the fix. Because the PRA allows five-year products to be stress-tested at the pay rate rather than the pay rate plus 2%, a five-year fix routinely supports a materially larger loan than a two-year one.
Property type matters too. Small HMOs are typically tested at 145%, large HMOs at 160% and multi-unit freehold blocks at 150%, reflecting the extra management risk. Where two rules collide, the lender applies whichever is higher.
Buy-to-let calculator FAQs
How much can I borrow on a buy-to-let mortgage?
What is the interest coverage ratio (ICR)?
Why does a five-year fixed rate let me borrow more?
How much stamp duty do I pay on a buy-to-let?
What is a good rental yield in the UK?
What is Section 24 and how does it affect my return?
Should I choose interest-only or capital repayment?
Where these figures come from
Stress testing follows the Prudential Regulation Authority’s SS13/16 underwriting standards. Stamp duty uses the SDLT bands for England and Northern Ireland from April 2025, Revenue Scotland’s LBTT bands and the Welsh Government’s LTT bands, including the additional-property surcharges of 5%, 6% and 4% respectively. Income tax bands are 2025/26 and frozen to 2028.
These calculators are for guidance and do not constitute financial or tax advice. Individual lenders apply their own criteria, and your own circumstances will change the answer. Check anything material with a qualified broker or accountant before you commit.
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