Interest Rate vs APR: The Critical Difference
When lenders advertise mortgage rates, they quote a headline interest rate, say, "4.5%". But that's not the true cost. The true cost is the APR (Annual Percentage Rate), which includes fees.
Interest Rate (The Headline Number)
This is the percentage of your loan you pay in interest each year. A 4.5% interest rate on a £200,000 mortgage costs you roughly £9,000 in interest in year 1.
APR (The True Cost)
This factors in the interest rate PLUS all fees (arrangement fee, valuation, lender's legal fees, etc.), expressed as an annual percentage rate. If the arrangement fee is 2%, that effectively raises your true cost above the headline rate.
Why the Difference Matters
Two lenders might offer 4.5% interest. But Lender A charges a 1% arrangement fee (APR 4.75%) while Lender B charges a 3% arrangement fee (APR 5.2%). Comparing headline rates misses a £10,000+ difference in cost.
Lenders are required to show APR prominently for this exact reason. When comparing offers, always look at the APR, not the headline interest rate. The APR tells you the true annual cost.
How Lenders Set Interest Rates
The Base Rate
The Bank of England sets the base rate (the interest rate on government borrowing). This isn't directly your mortgage rate, but it's the foundation.
Lender Margin
On top of the base rate (or indices like SONIA for floating rates), lenders add their margin. This is typically 2 to 3% above the base rate.
So if the base rate is 5.0%, a lender offering "base + 2.5%" would charge 7.5%.
Risk Premium
Different borrowers pay different rates based on risk:
- 80% LTV (20% deposit): Lowest risk, best rates (e.g., 4.5%)
- 85% LTV (15% deposit): Slightly higher risk, slightly higher rate (e.g., 4.7%)
- 90% LTV (10% deposit): Higher risk, higher rate (e.g., 4.9%)
- 95% LTV (5% deposit): Highest risk, highest rates (e.g., 5.2%)
This isn't discrimination, it reflects actual default risk. Borrowers with smaller deposits are statistically more likely to default.
Fixed vs Floating Rates and What You Pay
Fixed Rates
Your rate is fixed for the term (2, 5, 10 years, etc.). What you pay now is what you'll pay for the entire term, no surprises.
In April 2026, 5-year fixed rates typically range 4.2 to 5.5% depending on LTV and lender.
Tracker Rates
Your rate tracks the base rate plus a margin. If the base rate moves, your rate moves automatically.
Base rate + 2.5% = If base rate rises 1%, your rate also rises 1%.
Discount Rates
Your rate is the lender's Standard Variable Rate minus a discount. If the lender raises their SVR, your rate rises (but the discount stays the same).
SVR, 1.5%. If SVR rises from 6% to 7%, your rate rises from 4.5% to 5.5%.
The Real Monthly Cost: An Example
Let's see how a 1% difference in rate affects your monthly payment on a £200,000 mortgage over 36 years:
| Interest Rate | Monthly Payment | Total Interest (25 years) | Difference vs 4.5% |
|---|---|---|---|
| 4.0% | £927 | £77,062 | Save £14,000 |
| 4.5% | £1,009 | £91,155 | , |
| 5.0% | £1,061 | £104,769 | Pay £13,600 extra |
| 5.5% | £1,117 | £118,871 | Pay £27,700 extra |
| 6.0% | £1,199 | £133,445 | Pay £42,300 extra |
Notice: a 1% rise from 4.5% to 5.5% costs you £27,700 over 36 years, or £108/month more. This is why comparing rates matters enormously.
Fee Impact on True Cost
Here's how fees affect your true rate (APR). Using a £200,000 mortgage, 5-year fixed, headline rate 4.5%:
| Arrangement Fee | Headline Rate | Effective APR | Difference |
|---|---|---|---|
| 0% (fee-free deal) | 4.5% | 4.5% | , |
| 1% (£2,000) | 4.5% | 4.7% | +0.2% |
| 2% (£4,000) | 4.5% | 4.9% | +0.4% |
| 3% (£6,000) | 4.5% | 5.1% | +0.6% |
A 3% arrangement fee effectively raises your APR by 0.6%. That's significant.
Fee-Free Mortgages: The Trade-Off
Some lenders offer "fee-free" mortgages (0% arrangement fee). Sounds great, but there's always a trade-off:
- Higher headline rate: The headline rate is typically 0.3 to 0.5% higher to compensate for the missing fee
- Limited choice: Fee-free mortgages usually only available on specific products
- Limited flexibility: Early repayment penalties might be stricter
Whether fee-free is worth it depends on whether you'll repay early. If you're keeping the mortgage for the full term, a fee-free deal often works out no cheaper overall (higher headline rate cancels the fee saving).
Always compare complete offers: headline rate, APR, arrangement fee, early repayment penalties, and your personal situation. Don't cherry-pick one number.
Rate Factors Within Your Control
- Deposit size: Larger deposit = lower rate (see risk premium above)
- Credit score: Better credit = lower rate. Poor credit = higher rate or rejection
- Mortgage term: 5-year fixed vs 10-year fixed have different rates (typically 10-year costs more)
- Overpayment allowance: Mortgages with higher overpayment allowances often charge slightly higher rates
Rate Factors You Cannot Control
- Bank of England base rate: Out of anyone's control; set by the MPC
- Financial markets: Bond yields and economic outlook drive lender funding costs
- Lender competition: How many lenders are competing for your business affects rates
How to Get the Best Rate
- Save a larger deposit: 15%+ puts you in a better risk category immediately
- Improve your credit score: Pay bills on time, reduce debt, check for errors
- Use a mortgage broker: They access rates unavailable direct, and they submit to multiple lenders simultaneously
- Shop around: Get AIPs from 2 to 3 lenders before deciding
- Time your application wisely: Avoid applying during periods of market turmoil
Get Quotes from Multiple Lenders
A qualified mortgage adviser can obtain and compare rates from multiple lenders, showing you the true cost of each option.
Get Rate Quotes →Key Takeaways
- Always compare APR, not headline interest rates
- A 1% difference in rate costs £13,000 to £42,000 over 36 years
- Lenders set rates based on base rate + margin + risk premium (LTV)
- Arrangement fees effectively raise your true rate by 0.2 to 0.8%
- Fee-free mortgages trade low fees for higher headline rates
- Larger deposits and better credit scores get you lower rates
- Mortgage brokers can access rates unavailable directly to consumers
Important: This article is for general information and educational purposes only. It does not constitute financial or mortgage advice. Interest rates, APRs, fees, and lending criteria change constantly. This article is accurate as of April 2026. Before applying for a mortgage or making decisions based on rates, speak to a qualified mortgage adviser who can show you real rates for your specific circumstances. For personalised rate quotes and comparisons, contact DS Financial (Appointed Representatives of Stonebridge Mortgage Solutions Ltd, FCA Firm Ref: 835094, info@dsfinancial.co.uk or 0330 22 333 10).