Semi-Commercial Mortgage Calculators in 2026: Running the Numbers Before You Apply
Two brothers view a cafe with two studio flats above it on a Saturday morning in a Lincolnshire market town. The asking price is 400,000 pounds, the cafe tenant has six years left on the lease, and the agent wants an offer by Monday. Between the viewing and the offer they have five questions: how much would a lender advance, what deposit do they need, does the rent support that loan, what would a bridge cost if they had to complete in a month, and what is the stamp duty. None of those needs a lender yet. All five can be answered, roughly, with a semi-commercial mortgage calculator and its four companions, and doing that arithmetic before the offer is the difference between bidding with confidence and bidding blind. This article runs the cafe through each tool in turn, shows the figures the calculators produce, and then lists the things a lender will still check that no calculator can.
Semi-Commercial Property Finance, a trading name of Lenzie Consulting Ltd (company number 08174104), is a UK finance arranger and introducer, not a lender. Semi-commercial and mixed-use finance arranged for business and investment borrowers is unregulated lending and falls outside the Financial Conduct Authority’s regulated mortgage perimeter, so the business is not FCA authorised; where an individual borrower will personally occupy the residential element of the property the loan can fall under regulated rules and those cases are referred to a regulated firm. Every figure below is an indicative published band from semicommercialpropertyfinance.co.uk as of mid 2026, not an offer of finance.
In the episode below, Georgina runs a shop-and-flats purchase through the loan to value cap and the rent cap and shows which one wins.
Five questions, five tools
| The question before the offer | The calculator | What it needs from you |
|---|---|---|
| How much will a lender advance, and what deposit? | Semi-commercial mortgage calculator | Value, loan to value, rate, term |
| Does the rent support that loan? | Mixed-use affordability calculator | Commercial rent, residential rent, ICR, stress rate |
| What would a fast completion cost? | Semi-commercial bridging calculator | Loan, monthly rate, months, fee |
| Is it semi-commercial or residential to a lender? | Classification calculator | Floor area or value of each part |
| What is the stamp duty? | Mixed-use stamp duty calculator | Price |
Each tool answers one question. Buyers often run the first one and stop, because the loan to value figure is the largest and most flattering. The rent test usually produces the smaller number, and the smaller number is the loan.
Maximum loan and deposit from the loan to value
The semi-commercial mortgage calculator takes the value and the loan to value and returns the loan and the deposit. Across our lender panel, semi-commercial term mortgages on the indicative mid 2026 bands go up to 70 to 75 percent loan to value, so on the 400,000 pound cafe:
| Loan to value | Maximum loan | Deposit |
|---|---|---|
| 75% | 300,000 | 100,000 |
| 70% | 280,000 | 120,000 |
| 65% | 260,000 | 140,000 |
The brothers should plan on the 70 percent line, because 75 percent is the top of the band and depends on the strength of the case, and they should have the 65 percent figure in mind as the outcome if the valuation comes in light or the lender trims leverage for a shorter lease. That gives them a deposit range of 100,000 to 140,000 pounds before fees and tax.
The rent test, and why it usually sets the loan
An investment semi-commercial loan is sized on income, not on the borrower’s salary. The affordability calculator adds the commercial rent and the residential rent to a combined annual figure, then divides by the interest cover ratio and the stress rate. Suppose the cafe pays 18,000 pounds a year and the two studios 6,000 pounds each, a combined rent of 30,000 pounds. At a 130 percent interest cover ratio and a 9 percent stress rate the arithmetic is 30,000 divided by 1.30 divided by 0.09, which is about 256,000 pounds.
That is less than the 280,000 pounds the loan to value allowed. The real maximum loan is the lower of the two caps, so the rent, not the value, sets this loan at around 256,000 pounds and the deposit rises to about 144,000 pounds. Interest cover ratios across the lender panel run from 125 to 140 percent, and the stress rate moves with the lender and the product, so the same rent can support a noticeably different loan from one desk to the next. At 125 percent and the same stress rate the loan would be about 267,000 pounds; at 140 percent it would be about 238,000 pounds. Placing the case with the lender whose test gives the building the most borrowing is a large part of the value an arranger adds.
A calculator tells you the loan the arithmetic allows; a lender tells you the loan the building, the tenant and the borrower earn.
The mortgage calculator then turns the loan into a payment. On 256,000 pounds at 7.5 percent, inside the 6.5 to 8.5 percent band, interest only costs 1,600 pounds a month with the full balance still owed at the end. Capital and interest over 20 years is about 2,060 pounds a month and clears the loan; over 25 years it is about 1,890 pounds a month. Against 30,000 pounds of rent, the interest-only figure leaves 10,800 pounds a year before voids, repairs and tax, which is the cushion the interest cover ratio is designed to protect.
Bridging cost when the purchase cannot wait
If the vendor needs a four-week completion, a term mortgage will not get there and the bridging calculator becomes the relevant tool. Bridging on a mixed-use asset prices at about 0.70 to 0.95 percent a month, 8.5 to 11 percent a year, for 1 to 24 months at up to 70 to 75 percent loan to value. A 280,000 pound bridge at 0.85 percent a month over 9 months costs 2,380 pounds a month, 21,420 pounds of interest in total, plus a 2 percent arrangement fee of 5,600 pounds, so 27,020 pounds of cost and 307,020 pounds to repay if the interest is rolled up to exit. Valuation, legal and exit fees sit on top. The number that matters is not the monthly rate but the total cost against the exit, which here would be a term refinance at 6.5 to 8.5 percent once the rent is proven, and we line the term lender up before the bridge completes so the two are priced as one plan.
Classification and stamp duty: the two checks before the offer
Two more calculators settle questions that decide which lenders and which tax scale apply. The classification calculator applies the 40 percent rule. If the cafe with its prep kitchen is 1,400 square feet and the two studios are 400 square feet each, the residential share is 800 divided by 2,200, or about 36 percent, so the building reads as semi-commercial and stays with the specialist semi-commercial lenders, challenger banks and high street commercial desks. Had the flats been larger and the share come out at 40 percent or more, the case would lean residential and a different set of desks and tests would apply. Where the borrower will live in one of the flats the loan can become regulated whatever the percentage, and we refer those cases to a regulated firm.
The stamp duty calculator applies the non-residential Stamp Duty Land Tax scale for England and Northern Ireland: 0 percent on the first 150,000 pounds, 2 percent on the slice to 250,000 pounds and 5 percent above that. On 400,000 pounds that is 2,000 plus 7,500, a total of 9,500 pounds. On the residential additional-property scale the same price would attract 30,000 pounds, so the mixed-use treatment saves the brothers 20,500 pounds of day-one cash. Stamp duty is an HMRC matter, the mixed-use position can be challenged where the commercial part is token, and buyers should take their own advice from a conveyancer or accountant.
What a lender will still check that no calculator can
The calculators produce a plan: a loan of about 256,000 pounds, a deposit of about 144,000 pounds, tax of 9,500 pounds and a monthly payment between 1,600 and 2,060 pounds. A lender then checks the things the tools take on trust. The valuation may not match the price, and a lender lends on the lower of the two. The cafe lease is six years, and a lender will read the break clauses, the rent review and the tenant’s accounts before it counts 18,000 pounds as reliable income. The studios must be let on proper tenancies, with the rent evidenced by bank statements, not the agent’s estimate. The commercial part must be genuine and lettable, with its own access. The borrowers’ experience, credit history and, where the loan is to a limited company, personal guarantees will all be underwritten. And the interest cover ratio is tested at the lender’s own stress rate on the day, not the one the buyer typed in. None of that invalidates the arithmetic. It is where the application starts, and the file that follows is what earns the loan.
2026 outlook for the numbers
The Bank of England held base rate at 3.75 percent at its 30 July 2026 decision, with the next decision due on 17 September 2026, so the stress rates lenders use in their affordability tests have been steady through the summer and the 6.5 to 8.5 percent term band and the 0.70 to 0.95 percent monthly bridging band have moved little since spring. The practical advice for 2026 is to run the rent test at a stress rate a point above the pay rate the calculator suggests, because that is where most lenders sit, and to treat the 75 percent loan to value line as a ceiling rather than a plan.
FAQ
How does a semi-commercial mortgage calculator work out the maximum loan? It multiplies the property value by the loan to value, typically up to 70 to 75 percent on a mixed-use asset, and treats the rest as the deposit. On a 400,000 pound property at 70 percent that is a 280,000 pound loan and a 120,000 pound deposit. The rent test then caps the loan separately, and the lower figure applies.
What is the interest cover ratio on a mixed-use property? It is the headroom between the combined commercial and residential rent and the annual interest on the loan, tested at a stressed rate. Lenders commonly use 125 to 140 percent. At 130 percent and a 9 percent stress rate, 30,000 pounds of rent supports a loan of about 256,000 pounds.
Should I use interest only or capital and interest in the calculator? Run both. Interest only gives the lowest monthly cost and leaves the full loan to refinance or repay at the end; capital and interest costs more each month and clears the balance. On 256,000 pounds at 7.5 percent the figures are about 1,600 pounds a month against about 2,060 pounds over 20 years. Many investment cases start interest only and switch as the rent grows.
Are the calculator figures an offer of finance? No. They are indicative arithmetic on published bands. A real loan is sized on the valuation, the lease and tenancy evidence, the commercial and residential split, the borrower’s profile and the lender’s own stress test, and any facility is subject to full underwriting.
Talk to us
Run your own building through the semi-commercial mortgage calculator, then check the rent, the bridge, the classification and the tax across the full set of semi-commercial calculators. When the numbers look like they work, send us the value, the rent and the split and we will come back with the loan the lenders would actually offer within one working day. See also our affordability and interest cover guide for how the rent test is built.
All figures in this article are indicative published bands for UK semi-commercial and mixed-use finance in 2026, not an offer, a quote or a financial promotion, and any facility is subject to lender terms, valuation and full underwriting. This article was written by Matt Lenzie.
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