Calculator
BRRR calculator
The short version: a BRRR deal works when the refinance gives you back most of the cash you put in, and the rent still covers the new, larger mortgage. The two numbers that matter are the cash left in the deal after refinancing and the yearly rent left after costs and interest.
| Stamp duty at the additional-property rate | £4,750 |
| Refurbishment plus 10% contingency | £22,000 |
| Purchase loan | £71,250 |
| Cash in before refinance (deposit, stamp duty, legal costs, works) | £53,000 |
| New loan at refinance | £105,000 |
| Cash released after repaying the purchase loan | £33,750 |
| Interest on the purchase loan during the works (not included above) | £1,959 |
Net rent allows 25% of the rent for running costs, then takes off interest on the new loan. The value after works is an estimate until a lender's surveyor agrees it. Capital at risk: values and rents can go down as well as up.
How it works it out
- Cash in = deposit + stamp duty + legal costs + refurbishment with a 10% contingency.
- New loan = value after works × refinance loan-to-value.
- Cash released = new loan − the purchase loan it repays.
- Cash left in = cash in − cash released, and never less than zero.
- Net rent = yearly rent × 75% (a 25% allowance for running costs) − a year's interest on the new loan.
- Return on cash left in = net rent ÷ cash left in. If no cash is left in and the rent still covers the mortgage, it shows as all money out.
These are the same formulas DealSold uses on every BRRR listing. See the full methodology.
Worked example
A two-bed terrace bought for £95,000 with a 75% purchase loan of £71,250. Stamp duty at the additional-property rate is £4,750, because the whole price falls in the 0% band, so only the 5% surcharge applies. A £20,000 refurbishment becomes £22,000 with contingency. With £2,500 of legal and survey costs, the cash in is £53,000.
After the works a surveyor values it at £140,000. A 75% refinance gives a new loan of £105,000. Repaying the £71,250 purchase loan releases £33,750, so £19,250 is left in the deal.
Let at £900 a month, the rent is £10,800 a year. Take off 25% for running costs and £5,775 of interest at 5.5%, and £2,325 a year is left: a 12.1% return on the cash left in, before tax. Interest on the purchase loan during six months of works adds about £1,959 on top. If the surveyor valued it at £125,000 instead, the new loan would be £93,750 and £30,500 would stay in.
Check the rent against the lender's stress test
Buy-to-let lenders test whether the rent covers the interest with room to spare. Under the Bank of England's rules for buy-to-let lending, the test rate is at least 5.5% unless the mortgage is fixed for five years or more. Lenders then usually ask for rent of 125% of that interest for basic-rate taxpayers and limited companies, and 145% for higher-rate taxpayers. On the £105,000 loan above, that means about £602 a month at 125% and £698 at 145%. A low rent can cap the loan even when the valuation is good.
See how BRRR deals on DealSold are worked out
Every BRRR listing shows cash left in, the refinance assumptions and where each figure came from: verified, third-party or the sourcer's estimate.
Capital at risk. Property values and rents can go down as well as up.
How we made this
The calculator runs DealSold's own calculation code, which is tested against GOV.UK's stamp duty examples. Stamp duty uses the England and Northern Ireland rates from 1 April 2025. The worked example is illustrative, not a forecast. General information, not financial, tax or mortgage advice; speak to a qualified broker before you rely on a refinance.