Let-to-buy calculator
Let-to-buy means keeping your current home, remortgaging it onto a buy-to-let, and buying a new home to live in. You release equity from the old home as the deposit for the new one. The buy-to-let raise is capped at about 75% of the old home's value or by the rental cover test, whichever is lower; take off what you still owe and the rest is your deposit. You then need a residential mortgage on the new home that your income supports, with the let assessed alongside it.
Two mortgages, one move
Let-to-buy joins two deals. First, your current home is remortgaged onto a buy-to-let, which raises money against it. Second, that raised money becomes the deposit for a residential mortgage on your new home. The deposit you can release is set by the buy-to-let side:
Deposit released = lower of (75% of current value, rental cover limit) − amount you still owe
The rental cover limit is the same test as any buy-to-let: annual rent divided by the stress rate times the ICR. See the buy-to-let calculator for that part in full.
Worked example
Your current home is worth £350,000, you owe £150,000, and it would let for £1,400 a month. The 75% loan-to-value cap is £262,500. The rental cover cap at a 5.5% stress and 145% ICR is about £210,658. The lower of the two, £210,658, is the most you can raise. Take off the £150,000 you still owe and you release about £60,658 as a deposit for the new home. You then need a residential mortgage on the new property that your income supports.
Deposit released at 75% LTV (£350,000 home)
| Amount still owed | Equity released as deposit |
|---|---|
| £100,000 | £162,500 |
| £150,000 | £112,500 |
| £200,000 | £62,500 |
| £250,000 | £12,500 |
Assumes the 75% loan-to-value cap is the binding limit; the rental cover test can cap the raise lower. Indicative only, not a quote or advice. Last reviewed 24 July 2026.
Check it for real
Run your own figures and get matched
The example above shows the method. Use this let-to-buy calculator to run your own home value, balance and rent, and if you choose, be introduced to a regulated broker who can arrange both sides with lenders that welcome let-to-buy. Provided by our partner Propillo. Information, not advice, and no obligation.
Common questions
What is let-to-buy?
Let-to-buy is where you keep your current home and let it out, remortgaging it onto a buy-to-let mortgage, and buy a new home to live in with a residential mortgage. You raise money on the old home to fund the deposit on the new one. It suits people who want to move but cannot or do not want to sell first, for example a couple moving in together or a job relocation.
How much deposit can I release?
The buy-to-let raise on your current home is capped two ways: a loan-to-value limit, usually around 75% of its value, and the rental cover test on the expected rent. The lower of the two applies. Subtract whatever you still owe on the current mortgage, and what is left is the equity you can release as a deposit. On a £350,000 home with £150,000 owed, a 75% cap of £262,500 or a rent cap of around £210,000 (whichever is lower) leaves roughly £60,000 of deposit.
Will I be accepted for two mortgages at once?
You can hold both, but the residential lender on the new home assesses your affordability including the buy-to-let commitment. If the let is self-financing (the rent covers its mortgage) many lenders treat it as neutral, but the arrangement adds complexity. Some lenders like let-to-buy, others do not, which is exactly where matching to the right lender matters.
Does the stamp duty surcharge apply?
Usually yes. Because you will own two properties at completion, the higher rate of stamp duty (an extra 5% in England and Northern Ireland from late 2024) normally applies to the new home, even though it is your main residence, because you are not replacing your only property. The rules are detailed and there are reliefs and time limits. This is not tax advice: check gov.uk or a tax adviser for your case.
Related: the buy-to-let calculator, how much can I borrow for the residential side, and stamp duty thresholds for the surcharge.
Founder, MortgageExplained
Adam spent nearly a decade as a mortgage adviser at Just Mortgages, with further experience in commercial finance. He is CeMAP and CF qualified. He built MortgageExplained to do one thing well: explain mortgages in plain English, then introduce you to a regulated broker when you are ready. Every page is written and reviewed by Adam.
Last reviewed: 24 July 2026