Buy to Let Mortgage Calculator

Whether you’re simply considering a buy-to-let mortgage, or rather expanding your existing portfolio, our buy-to-let calculator allows you to check if you’re eligible as well as what sort of figure you can expect from a lender.

Calculator placed next to house models

How much can I borrow?

How much you could borrow for a buy-to-let mortgage depends on a specific set of your personal details. Put these into the calculator below and we’ll provide you with an indication of your borrowing potential.

We could help you borrow up to: £350,000 Please note this does not guarantee eligibility for a mortgage and will still be subject to suitability and your credit profile. To ensure we can get you the best personalised mortgage quote please reach out to us.

What is a buy-to-let mortgage calculator?

Simply put, a buy-to-let calculator is a tool which helps you work out the loan amount you could receive from a lender for a property you want to rent out.

If you’re purchasing a property with the intention of letting it out, it’s important that you know exactly how much your monthly mortgage repayments will cost in addition to how much you can likely afford to borrow. Our buy-to-let mortgage calculator does just this for you.

How do lenders calculate buy-to-let mortgages?

Borrowing on a buy-to-let mortgage is fundamentally determined by the prospective rental income you are able to get on a property. In general, lenders will want to see your rental income exceed your mortgage repayment total by 25% or more.

To offer an example, if you were going to pay £800 on a buy-to-let mortgage each month, your monthly income gained from rent would have to be at least £1,000.

Other significant factors for calculating buy-to-let mortgages include your loan-to-value (LTV) ratio - which is often required to be 85% or lower - alongside your annual income.

How much will my buy-to-let mortgage cost?

The cost of your buy-to-let mortgage will be influenced by three things:

  • Deposit size: A larger deposit reduces the borrowed amount. Typically, buy-to-let lenders require around 25% of the property’s value.

  • Interest rate: Monthly payments for buy-to-let mortgages cover only the interest, not the entire capital loan amount.

  • Mortgage term: The complete mortgage amount is settled by you at the end of the loan term.

What are the interest rates on buy-to-let mortgages?

Your offered interest rate from a buy-to-let mortgage lender is down to:

  • Your LTV ratio: A higher ratio increases the loan's risk and usually leads to a higher interest rate.

  • Your credit history: Lower credit scores often result in higher mortgage interest rates due to perceived risk by lenders.

  • The current Bank of England (BoE) base rate: Mortgage rates are directly influenced by the BOE’s base rate.

  • Mortgage type: A fixed-rate mortgage maintains a consistent interest rate, while a variable-rate mortgage fluctuates over time.

Company Information

The Mortgage Genie Limited is Registered in England and Wales with Company Number 9803176. The Mortgage Genie Limited is an Appointed Representative of PRIMIS Mortgage Network. PRIMIS Mortgage Network is a trading name of First Complete Ltd which is authorised and regulated by the Financial Conduct Authority for mortgages, protection insurance and general insurance products. The Financial Conduct Authority does not regulate some forms of Buy to Let.


Your initial mortgage consultation is always free of charge. Depending on the complexity of your mortgage there may be a fee for our mortgage advice and arrangement service, which will be discussed and agreed before you make a mortgage application. A typical fee is £293 and will never be more than 1% of the mortgage amount.