Buy-To-Let
CALCULATOR 2026/27
Drummonds Finance Group
With buy-to-let, it's the rent that decides how much you can borrow, not your salary. Every lender runs its own rental stress test, so the same property can get very different results depending on the lender, the rate you choose and whether you buy personally or through a limited company.
Use our free buy-to-let calculator to see your maximum borrowing in seconds. Enter the purchase price, your deposit and the expected monthly rent to check whether your rent passes the lender's stress test, how much rent you'd need for the mortgage you want, and what your rental yield and monthly cash flow could look like after costs.
Whether it's your first rental property, your next addition to a portfolio or a limited company purchase, speak to Drummonds Finance Group on 0330 1330034. As whole-of-market brokers, we'll find the lender that gives you the most borrowing at the best rate for your investment.
Speak to a Mortgage Adviser
Find out what mortgage rate are available for you.
How does the buy to let calculator work?
Our calculator follows the same steps a buy to let lender uses:
- It takes the monthly rent and tests it against a stress interest rate, using the Interest Cover Ratio (ICR) for your situation
- It compares that figure with the maximum loan to value, usually 75%, and gives you whichever is lower as your maximum borrowing
- It checks whether the mortgage you actually need passes, and shows the minimum rent required
- It works out your gross rental yield, monthly cashflow after costs and return on your deposit
You can change the stress rate and maximum LTV to match different lenders and products.
How much rent do I need for a buy to let mortgage?
The rent you need depends on the loan size, the stress rate and your ICR. Here's the minimum monthly rent most lenders would want, tested at 5.5%:
£150,000 mortgage
- Limited company or basic rate taxpayer (125%): £860 a month
- Higher rate taxpayer (145%): £997 a month
£200,000 mortgage
- Limited company or basic rate taxpayer (125%): £1,146 a month
- Higher rate taxpayer (145%): £1,330 a month
£250,000 mortgage
- Limited company or basic rate taxpayer (125%): £1,433 a month
- Higher rate taxpayer (145%): £1,662 a month
£300,000 mortgage - Limited company or basic rate taxpayer (125%): £1,719 a month
- Higher rate taxpayer (145%): £1,994 a month.
Enter your own figures in the calculator above to see the exact rent needed for your mortgage.
How do I calculate rental yield?
Gross yield = (monthly rent × 12) ÷ purchase price × 100
A £250,000 property renting for £1,350 a month has a gross yield of 6.48%.
Many investors look for a gross yield of 5% to 7%, with higher yields often found in the North of England, the Midlands and with HMOs. Net yield takes off running costs such as letting fees, insurance, maintenance and service charges, so it gives a truer picture of what the property earns.
How do I work out buy-to-let cash flow?
Monthly cash flow = rent − mortgage payment − letting fees − other running costs
Example: a £250,000 property with a £187,500 interest only mortgage at 5%, renting for £1,350 a month:
- Rent: £1,350 - Mortgage interest:
−£781 - Letting and management at 10%:
−£135 - Insurance, maintenance and other costs:
−£100 - Monthly cash flow before tax: around £334
That's about £4,000 a year, or a 6.4% return on a £62,500 deposit. Always leave a buffer for void periods, repairs, and future rate rises.
Ready to find your buy to let mortgage?
Once you know your numbers, the next step is finding the right lender. Deposits, limited company purchases, first-time landlords, portfolio landlords, HMOs, and holiday lets all have their own criteria.
Find out more on our buy-to-let mortgages page, or call us for a free chat about your plans.
Specialist Mortgages
Not every mortgage fits a lender's computer model. Much of our work at Drummonds Finance Group is with clients who have been turned down elsewhere or told their case is too complicated. We work with clients across the UK by phone and video, and we know which lenders will look at each situation properly.