APR vs Interest Rate Calculator
Understand the difference between APR and interest rate and compare loan true costs.
What this calculator does
This calculator turns a quoted interest rate plus the fees attached to a loan into the APR that describes the real cost of borrowing. Enter the amount, the nominal rate, the total fees, the term, and your tax rate, and it returns the true APR alongside the nominal rate and the after-tax cost of the debt.
The gap between the two figures is where lenders compete without appearing to. Two mortgages advertised at 5.25 percent can carry a £0 fee and a £1,995 fee respectively, and only a total-cost view reveals the difference. FCA rules require APR disclosure precisely so that comparison is possible.
When to use it
Use it whenever you are holding two quotes with different rate and fee combinations, which describes almost every UK mortgage comparison. A lender offering 0.2 percentage points less for a £1,500 higher product fee is making a trade whose value depends entirely on your loan size, and this converts it into a single number.
It is particularly useful for the fee-versus-rate decision on smaller mortgages, where fixed fees weigh heaviest. And treat the APRC on a mortgage illustration with caution — because it assumes you spend the remainder of the term on the standard variable rate, it rarely reflects what a borrower who remortgages every few years actually pays.
Understanding the inputs
Loan amount is the capital borrowed. Nominal interest rate is the headline rate that determines your monthly payment. Total loan fees should capture everything compulsory: product or arrangement fees, booking fees, lender valuation fees, and any broker fee you are charged directly.
Loan term in years determines how far those fees are spread, and it is what drives the gap between the nominal rate and the APR. A £1,495 fee across 25 years barely registers; the same fee on a two-year deal is a substantial addition. If you remortgage every few years, run the term as your deal period rather than the full mortgage term.
How is this calculated?
APR = ((Fees / Loan Amount) / Term + Nominal Rate) × 100. APR includes fees, making it the true cost of borrowing.
A worked example
Take a £200,000 mortgage at 5.25 per cent with a £1,495 product fee over a 25-year term. The monthly repayment, driven by the rate, is about £1,199, and spreading the fee across the full term lifts the effective annual cost to roughly 5.33 per cent — a difference of only eight basis points.
Now treat it as what it really is: a two-year fixed deal. Spread across two years rather than 25, that same £1,495 is worth around 0.37 percentage points a year on the loan. On a £100,000 mortgage it would be closer to 0.75 points. That is why the fee-free version of a product at a slightly higher rate often wins on smaller loans.
Limitations and assumptions
The calculator solves for the true rate numerically rather than approximating it, but it assumes fees are paid upfront rather than added to the loan, a fixed rate for the whole term, and that you hold the mortgage to maturity. UK mortgages fix for two to five years and then revert, so none of those hold for long.
The APRC a lender must quote assumes you stay on the product to the end of the term including the reversion rate, which is why it can look alarming and is rarely the number that matters to you. Your lender's illustration is the binding document, and a broker can model the deal-period total cost that actually decides between products.
Common Questions
- What is the difference between APR and the interest rate?
- The interest rate sets your monthly payment. The APR is a standardised figure required by the FCA that folds in compulsory fees and charges, so borrowers can compare products on a single basis. Where a loan carries no fees they are the same number; where it carries a product fee, the APR is higher.
- What is APRC and when does it apply?
- APRC — annual percentage rate of charge — applies to mortgages under the Mortgage Credit Directive. It shows the total cost over the whole mortgage term assuming you move onto the lender's standard variable rate once the deal period ends. That assumption makes APRC nearly useless for comparing two-year fixes, since almost nobody stays on SVR for 23 years.
- Why can a higher-fee mortgage still be cheaper?
- Because the fee is fixed while the rate saving scales with the loan size. A £1,495 product fee buying a 0.3 point lower rate is excellent value on a £400,000 mortgage and poor value on a £100,000 one. Compare total cost over the deal period, which is what genuinely matters.
- What is representative APR and am I entitled to it?
- For consumer credit, an advertised representative APR must be offered to at least 51 percent of applicants the lender accepts. The other 49 percent can be quoted more. It is a genuine rate, but not a guaranteed one, so use a soft-search eligibility check before applying rather than budgeting on the headline.
- Which fees go into a mortgage APRC?
- Product and arrangement fees, valuation fees where the lender requires them, and any compulsory insurance. Conveyancing costs you arrange yourself, stamp duty, and voluntary surveys sit outside it. That is why two mortgages with the same APRC can leave you with quite different bills at completion.
- Does APR mean the same on a credit card?
- No. Card APR is the annualised interest rate on borrowing, with the annual fee included where one exists but with cash advance and balance transfer fees excluded. There is no fixed term to spread costs across, so card APR is much closer to a plain interest rate than a mortgage APRC is.
- How does APR relate to AER on savings?
- They are mirror measures. APR describes what borrowing costs, AER what saving earns once compounding is accounted for. Comparing the two is the right way to decide whether to overpay a loan or save the money — and with UK loan APRs typically well above savings AERs, overpaying usually wins.
- Can I negotiate the fees behind the APR?
- Mortgage product fees are generally fixed by the product rather than negotiable, but most lenders let you add the fee to the loan or pay it upfront — and adding it means paying interest on it for the whole term. Brokers can sometimes access fee-free versions of the same product, which is worth asking about.