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Flat rate vs reducing rate: why the same "4%" loan can cost twice as much

Car and personal loans are often quoted at a flat rate that looks cheap. See how flat and reducing-balance interest compare, with worked examples.

Calculators2 min readUpdated

Key takeaways

  • A flat rate charges interest on the full original amount for the whole term.
  • A reducing (diminishing) balance rate charges interest only on what you still owe.
  • Over five years, a 4% flat rate costs about the same as a 7.4% reducing rate.
  • Always compare loans using the reducing rate or APR, not the flat rate.
On this page
  1. Two ways to quote the same loan
  2. A worked example
  3. A quick rule of thumb
  4. Other costs to check
  5. Questions to ask the lender

For information only, not financial advice. Ask lenders for the reducing-balance rate or APR and the full fee schedule before you borrow.

Two ways to quote the same loan

With a flat rate, interest is calculated once on the amount borrowed and spread evenly across the term: interest = principal × flat rate × years. With a reducing (or diminishing balance) rate, interest each month is charged only on the remaining balance, so it falls as you repay. Most mortgages use reducing rates; car and personal loans in many markets are advertised with flat rates because the number looks lower.

A worked example

Borrow AED 100,000 for 5 years (60 months).

4% flat4% reducing
Total interest100,000 × 4% × 5 = AED 20,000about AED 10,500
Monthly paymentAED 2,000about AED 1,842

The flat-rate loan costs nearly twice as much interest, because you keep paying interest on money you have already repaid. To match AED 2,000 a month over 60 months, a reducing-rate loan would need about 7.4%. That is the comparable rate.

A quick rule of thumb

For terms of 3–5 years, the equivalent reducing rate is roughly 1.8–1.9 times the flat rate. Use the loan calculator with a reducing rate to see the real monthly payment, total interest and an amortisation schedule.

Other costs to check

  • Processing or arrangement fees (often a percentage of the loan)
  • Mandatory insurance (life or vehicle)
  • Early settlement fees, which matter if you might repay early
  • Whether the rate is fixed or variable

Questions to ask the lender

  1. What is the reducing-balance rate or APR?
  2. What is the total amount I will repay, including all fees?
  3. What does it cost to settle early?

Sources

  1. UAE Central Bank: consumer protectioncentralbank.ae
  2. Investopedia: Amortized loan explainedinvestopedia.com
Written by the Toolkeel team at Sole Digital Media

Fact-checked against the sources above. We test every tool we mention. Editorial policy.

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