Short answer
- Formula: Payment = Principal × r × (1+r)n / ((1+r)n - 1).
- On personal and car loans r = contractual rate × 1.3 (KKDF 15% + BSMV 15%). Mortgages are exempt.
- ₺100,000 at 3.50% a month over 12 months: payment ₺10,998, total repaid ₺131,976.
- When comparing offers, look at the total repaid, not the monthly payment.
The fixed (annuity) installment formula
Most personal, car and home loans in Turkey are repaid in fixed installments using the annuity method. You pay the same amount every month, but the interest share inside it falls each month and the principal share rises.
P = principal (amount borrowed)
r = monthly interest rate (including taxes)
n = term (months)
The effect of KKDF and BSMV
On personal and car loans, 15% KKDF and 15% BSMV are charged on the interest paid each month. That is why the calculation uses 1.3 times the contractual rate:
Mortgages are exempt from KKDF and BSMV, so for a mortgage r equals the contractual rate.
Worked example
₺100,000 personal loan, 3.50% monthly contractual rate, 12-month term:
(1 + 0.0455)12 ≈ 1.7058
Payment = 100,000 × 0.0455 × 1.7058 / (1.7058 - 1) ≈ ₺10,998
First months of the schedule
| Month | Payment | Principal | Interest | KKDF | BSMV | Remaining |
|---|---|---|---|---|---|---|
| 1 | ₺10,998 | ₺6,448 | ₺3,500 | ₺525 | ₺525 | ₺93,552 |
| 2 | ₺10,998 | ₺6,741 | ₺3,274 | ₺491 | ₺491 | ₺86,811 |
| 3 | ₺10,998 | ₺7,048 | ₺3,038 | ₺456 | ₺456 | ₺79,762 |
| ... | ||||||
| 12 | ₺10,998 | ₺10,519 | ₺368 | ₺55 | ₺55 | ₺0 |
About 41% of the first payment goes to interest and taxes; by the last month that falls to 4%. That is why early repayment saves the most interest early in the loan.
Total repaid and interest cost
A longer term lowers the monthly payment but raises the total cost fast. ₺100,000 personal loan, 3.50% monthly contractual rate:
| Term | Monthly payment | Total repaid | Interest and taxes |
|---|---|---|---|
| 12 months | ₺10,998 | ₺131,976 | ₺31,976 |
| 24 months | ₺6,933 | ₺166,396 | ₺66,396 |
| 36 months | ₺5,698 | ₺205,142 | ₺105,142 |
The rate is an example; your bank's offer and extra fees such as arrangement fees change the result. TCMB's policy rate was 37% in September 2026.
Practical tips
- Keep installments under 30% of income: Add up all installments including card installments; see tracking installments.
- Keep the term as short as you can afford: The shortest affordable term has the lowest total cost.
- Ask about fees: Arrangement fees, insurance and appraisal costs add to the total.
- Make early payments: Extra payments early in the loan cut interest the most.
- Check whether a loan should replace card debt: Compare the monthly cost of both including taxes; our debt repayment plan has an example.
See the payment and schedule instantly with our free loan calculator; once you take the loan, let butce.app track the remaining installments.
Open CalculatorYou have calculated it. What next?
Once the loan is taken, the real work begins: paying on time every month, recording early payments and following the remaining principal. In butce.app, once you set up a loan its installments are placed in the financial calendar, each payment is deducted from your account, and early payments and restructuring can be recorded. Seeing card debt and loan installments together in one dashboard is the key check before any new borrowing decision.
Frequently asked questions
How is a loan installment calculated?
Fixed-installment loans use the annuity formula: Payment = Principal x r x (1+r)^n / ((1+r)^n - 1). r is the monthly interest rate and n the term in months. On personal and car loans in Turkey, r is taken as 1.3 times the contractual rate because 15% KKDF and 15% BSMV are added to the interest.
What are KKDF and BSMV, and do they apply to mortgages?
KKDF (Resource Utilization Support Fund) and BSMV (Banking and Insurance Transactions Tax) are charged on the interest of consumer loans in Turkey, 15% each on personal and car loans. Mortgages are exempt from both.
How much more does a longer term cost?
For a 100,000 TL personal loan at 3.50% a month, the total repaid is about 132,000 TL over 12 months, 166,400 TL over 24 months and 205,100 TL over 36 months. The monthly payment falls, but total interest grows fast.
Do I pay interest if I repay early?
When you repay early you pay the remaining principal plus interest accrued so far, not interest for future months. On fixed-rate consumer loans the bank may charge an early repayment fee, which is capped by law. Check the current terms in your contract and with your bank.
Sources
butce.app Editör Ekibi
This guide was written by the team behind butce.app, a budgeting app for tracking income, expenses, card installments and loans. Figures were checked against the official sources listed above; the article was last reviewed on .
This content is general information, not investment, tax or legal advice. Rates change, so check the official source before you decide.
