Flat vs reducing interest rate: what your loan really costs
Gulf banks often quote personal and car loans at a flat rate. It looks cheap, but it charges interest on money you have already paid back. Here is how the two methods work, what a flat rate really costs, and how to compare offers fairly.
How a flat rate works
With a flat rate, the bank works out interest once, on the amount you borrow, for every year of the term. That interest is added to the loan and the total is split into equal monthly instalments.
Interest = amount × flat rate × years
Monthly instalment = (amount + interest) ÷ months
AED 100,000 at 4% flat for 4 years: interest = 100,000 × 4% × 4 = AED 16,000. The instalment is 116,000 ÷ 48 = AED 2,416.67.
The catch: by the last year you owe only a small part of the loan, but interest is still being charged as if you owed all AED 100,000. Spread evenly, every month carries AED 333.33 of interest, including the last one, when the balance left is only about AED 2,400.
How a reducing rate works
With a reducing (or "declining balance") rate, each month's interest is the monthly rate times the balance still owed. Instalments stay equal, so the interest part shrinks and the repayment part grows over time. Mortgages, credit cards and the APR all work this way.
Monthly rate r = annual rate ÷ 12
Instalment = amount × r ÷ (1 − (1 + r)−months)
AED 100,000 at 4% reducing for 4 years: the instalment is AED 2,257.91 and total interest is AED 8,379.46. Interest in month 1 is AED 333.33 (100,000 × 4% ÷ 12), in month 24 about AED 180, and in the last month only about AED 7.50.
Side by side: the same loan both ways
| AED 100,000 over 4 years | 4% flat | 4% reducing | 7.47% reducing |
|---|---|---|---|
| Monthly instalment | 2,416.67 | 2,257.91 | 2,416.49 |
| Total interest | 16,000.00 | 8,379.46 | 15,991.54 |
| Total repaid | 116,000.00 | 108,379.46 | 115,991.54 |
The first and last columns are almost identical: 4% flat is a 7.47% reducing loan. The middle column shows what "4%" would cost if it really were a reducing rate.
Example 2: a car loan
AED 80,000 at 2.99% flat over 5 years: instalment AED 1,532.67, interest AED 11,960. Its reducing equivalent is 5.62%. A competing offer at 5.49% reducing costs AED 1,527.72 a month and AED 11,663 in interest, so it is slightly cheaper even though "5.49%" looks almost twice as high.
Example 3: a short loan
SAR 200,000 at 5% flat over 3 years: interest SAR 30,000, instalment SAR 6,388.89. The reducing equivalent is 9.31%; a true 5% reducing loan would cost SAR 15,790 in interest, about half.
Flat to reducing conversion table
Each cell is the reducing rate that gives the same instalment as the flat rate on the left, worked out with the same method as our personal loan calculator.
| Flat rate | 1 year | 2 years | 3 years | 4 years | 5 years |
|---|---|---|---|---|---|
| 2.5% | 4.58% | 4.73% | 4.76% | 4.75% | 4.73% |
| 3% | 5.49% | 5.66% | 5.68% | 5.67% | 5.64% |
| 3.5% | 6.40% | 6.58% | 6.60% | 6.58% | 6.54% |
| 4% | 7.30% | 7.50% | 7.51% | 7.47% | 7.42% |
| 5% | 9.10% | 9.32% | 9.31% | 9.24% | 9.15% |
| 6% | 10.90% | 11.13% | 11.08% | 10.97% | 10.85% |
These figures leave out fees. Processing fees, insurance and other charges push the true cost (the APR) higher still.
How to compare bank offers
- Ask whether the rate is flat or reducing. If the offer does not say, ask in writing.
- Ask for the APR. It is a reducing-balance rate that includes most fees, so it is the fairest single number.
- Convert any flat rate with the table above or the loan calculator before comparing it with a reducing rate.
- Compare total cost, not the instalment. A longer term lowers the instalment but raises the interest.
- Add the fees: processing, life insurance, and for car loans, vehicle insurance if the bank arranges it.
- Check early settlement terms. Ask how the settlement amount is worked out and what fee applies.
- Check that the instalment fits your salary cap. Banks cap repayments as a share of salary; our DBR calculator shows how much you can borrow.
What the regulators require
UAE. The Central Bank's Consumer Protection Standards require banks and finance companies to give you the expected annual interest or profit rate (clause 2.1.1.22(h)) and the expected Annual Percentage Rate (clause 2.1.3.2) before you sign. They must also say whether early settlement is allowed and which fees apply (clause 2.1.3.7), and when an advert shows an APR for a loan it must also show the total interest and fees over the term, by example (clause 2.3.3.2). The standards do not ban flat rates, so you will still see them in adverts.
Saudi Arabia. SAMA issued Rules Governing the Calculation of the Annual Percentage Rate in 2023 "to improve disclosure practices for consumers", in force 90 days after publication, so every lender works out the APR the same way. Ask for it on any offer.
Qatar. We could not read Qatar Central Bank rules on loan rate disclosure (the QCB site blocks automated reading), so ask your bank for the reducing-balance equivalent or APR in writing.
Common mistakes
- Comparing a flat rate with a reducing rate directly. 3% flat is not cheaper than 5.5% reducing; it is about the same.
- Judging by the instalment alone. Two loans can have the same instalment and very different total costs if the terms differ.
- Assuming early settlement refunds interest evenly. Ask for the settlement letter before you decide.
- Ignoring fees. A low-rate loan with a high processing fee can cost more than a higher rate with none.