Free tool
UK SME loan calculator & rate stress test
Work out the real monthly cost of a business loan, see the total interest you will pay, and stress-test the rate at +1% to +3% before you sign. With UK borrowing costs sitting at their highest level since the late nineties, a loan that looks fine today can bite hard if your rate is variable or you need to refinance.
Quick answer
A £50,000 loan over 5 years at 9% APR costs about £1,037.92 a month and £12,275.20 in total interest. If rates rise 2 points, that jumps to roughly £1,087.12 a month. Run your own numbers below — nothing is sent anywhere, it all calculates in your browser.
| Scenario | Rate | Monthly | Total interest | vs now |
|---|
Enter an amount to see the working.
Why stress-test your business loan now
UK borrowing costs have climbed back to levels not seen since the late 1990s, and gilt yields have spent this autumn at multi-year highs. For a small business that means three things:
- Variable-rate loans and overdrafts reprice quickly. A base-rate or tracker loan can move within weeks, not years.
- Refinancing is pricier than it was. If your fixed deal ends, the new quote may be several points higher than the one you signed.
- Cash-flow headroom matters more than the headline rate. A 2-point rise on a £50k loan is roughly £50–£60 a month — annoying on a repayment loan, painful on interest-only with a big balloon at the end.
The table above shows your payment at the rate you enter, then +1, +2 and +3 percentage points. If any of those rows would break your monthly budget, that is your answer: fix the rate, shorten the term, or borrow less.
How the calculation works
Repayment loans use the standard amortisation formula: monthly payment = P × r × (1+r)n ÷ ((1+r)n − 1), where P is the loan amount, r is the annual rate divided by 12, and n is the number of months. Total interest is the total of all payments minus the principal.
Interest-only loans charge P × r each month, with the full principal still owed as a balloon payment at the end of the term — the calculator flags that separately because it is the bit that catches people out.
Affordability bands: under 10% of monthly profit is comfortable, 10–25% is manageable, 25–40% is tight, and over 40% is a red flag most lenders (and most insolvency practitioners) would take seriously.
Numbers you can trust before you commit
If your management figures do not reconcile, every decision — including borrowing — is a guess. I help UK SMEs get clean, trusted reporting across ERP, Excel and Power BI.
Book a 30-minute data risk callThis calculator is for guidance only and does not constitute financial advice. Lenders may quote rates differently (flat rate vs APR), add arrangement fees, or use daily interest — always check the lender's own illustration. Built by Digital Adaption, October 2026.