Your semi-commercial mortgage calculator.
Change the assumptions to understand the arithmetic. This is an illustration, not a quote, affordability assessment or lending decision.
Assumes a constant rate and monthly payments for the entire term. Excludes fees, insurance, taxes, interest-rate changes and early repayment charges.
What the calculator cannot tell you
These payments do not indicate how much a lender will offer. Lenders may use rental coverage or debt-service tests, their own valuation and other criteria. A financially affordable payment in your budget is not the same as a lending approval.
Interest only means capital still needs repaying
With interest-only borrowing, the monthly amount covers interest and does not pay down the loan. You need a credible plan to repay the capital at the end. The total-repaid figure includes that final capital amount.
Read the guide to rates and fees or understand deposits and LTV.
How does the semi-commercial mortgage calculator work?
The calculator subtracts your deposit or equity input from the property value to produce an illustrative loan amount. It then applies your assumed annual interest rate, chosen term and repayment basis. The output shows the monthly payment, loan-to-value, total interest and capital remaining at the end. None of those inputs is a statement of commercial mortgage criteria.
Use it to explore arithmetic for a mixed-use property containing commercial and residential elements. Commercial mortgage lenders may use different values, income assumptions or loan terms in their assessment. A property price entered here is your assumption, not a valuation accepted by a lender. The calculator does not request a credit search or send an application.
What is the difference between capital repayment and interest-only?
With capital and interest repayment, each scheduled payment includes interest and a reduction of the outstanding loan. The calculation assumes monthly payments and a constant interest rate for the entire mortgage term. Under those assumptions the capital balance reaches zero at the end, subject to normal rounding differences. Real product terms and payment schedules can differ.
With interest-only, the payment covers interest but does not pay down principal. The full illustrative loan remains to be repaid at the end. The total-repaid output includes that final principal payment. A smaller monthly amount therefore does not mean the debt disappears or that the mortgage is the lower-cost or more suitable option.
How are monthly repayments calculated?
For a capital repayment illustration, the calculation uses the loan amount, the annual rate divided by twelve and the number of monthly payments. It applies the standard amortisation formula. If the assumed rate is zero, it divides the principal equally across the term. This zero-rate option is mathematical functionality, not an advertised interest-free mortgage.
For interest-only, a hypothetical £300,000 loan at a constant 6% annual rate produces £1,500 monthly interest: £300,000 × 0.06 ÷ 12. At a hypothetical 8%, it produces £2,000 monthly interest. The £500 difference illustrates sensitivity to the rate. Both examples exclude fees and leave £300,000 principal outstanding; neither is an available product quote.
Why is loan-to-value different from rental coverage?
Loan-to-value, or LTV, is the loan divided by the property value used in the calculation. It says nothing by itself about the income available to meet repayments. A commercial property can appear to have substantial equity yet generate insufficient acceptable rent or business income for the requested debt. Mortgage lenders consider their own criteria and the actual borrower and security.
Interest coverage and debt-service tests compare acceptable income against assumed interest or debt costs. Lenders may use stress rates, costs and different treatment of commercial leases, residential rent or vacant units. This calculator does not provide a universal ICR or DSCR approval test. Keep each tenant, income stream and expense clear when preparing a separate finance enquiry.
Which costs are excluded from this illustration?
The result excludes arrangement fees, valuation and legal costs, tax, insurance, maintenance, early repayment charges and any intermediary fee. It does not capitalise fees or model a rate change during the term. A commercial mortgage calculator is therefore only one part of assessing the cash needed for a purchase, refinance or investment.
Confirm whether a proposed fee is payable separately, added to the mortgage or deducted from the advance. A gross loan is not always the net cash available at completion. Compare products over the same period and on the same repayment basis, recording any balance remaining. Public mortgage rates should be read with their conditions and are not personal offers.
Can you model a fixed or variable mortgage rate?
You can enter any assumed rate within the calculator’s mathematical limits, but the model keeps that rate constant throughout the chosen term. A fixed rate may only apply for an initial period. A variable rate, including one linked to a reference such as the Bank of England base rate, can change under its contract. Neither pattern is reproduced automatically here.
To explore your budget, run a second illustration with a higher assumed rate and compare the monthly payment. This is a sensitivity exercise rather than a forecast of interest rates. It cannot tell you the rate a lender will offer, guarantee an affordable payment or establish that refinancing will be available when an initial period ends.
Does the ownership or property type change the result?
The arithmetic does not change because a company owns the property or because a shop occupies the ground floor. The lending assessment can change significantly. Limited companies, owner-occupied business premises and investment properties may need different information. A whole mixed-use building is also different from a flat-only purchase above commercial premises.
For an enquiry, describe the commercial and residential units, leases, actual rent, vacancies, borrower and source of deposit. Disclose any personal or related-person occupation. Do not use a repayment figure to decide the regulatory classification. Lenzie Consulting Ltd only deals with non-regulated finance and refers regulated funding requirements to an FCA-regulated counterparty.
Can this calculator compare bridging loans and term mortgages?
This is a monthly mortgage-repayment illustration. It does not model retained interest, rolled-up interest, staged drawdowns, exit fees or other structures that may be relevant to bridging loans or development finance. A short-term facility needs a clear purpose, cost assessment and repayment exit, separate from the calculation for a long-term mortgage.
If your property needs works before it can support a term mortgage, explain the current condition and future plan. A projected refinance or sale is not committed funding. We do not infer that a commercial lender will accept the property because the calculator produces a manageable-looking payment.
What is the next step after exploring the numbers?
Keep a note of your assumptions and the questions they raise. Prepare the address, price or value estimate, proposed loan, deposit, current income, intended ownership and timetable. For a remortgage, include the existing debt and known exit terms. These facts help put the repayment illustration in context.
An enquiry through this site starts a discussion within our non-regulated service. It is not a mortgage application, a valuation or a promise of an offer. Lenzie Consulting Ltd is not authorised or regulated by the FCA. Regulated requirements are referred to an FCA-regulated counterparty, responsible for its own assessment and any regulated advice.
Explore local property evidence before discussing the actual building.