Loan Calculator with Amortisation Schedule
The loan calculator computes the monthly annuity payment on a mortgage, consumer or business loan, the total interest paid over the term, and the full amortisation schedule. The schedule shows, for each year, how much of your payments goes to interest and how much repays principal, along with the outstanding balance. The early repayment simulation shows how many years and how much interest each extra euro added to the monthly payment saves.
Early repayment simulation
Formula and explanation
M = P · i · (1 + i)n / ((1 + i)n − 1)
where: P = loan amount (principal), i = monthly interest rate (annual rate ÷ 12), n = number of monthly payments, M = monthly payment. The interest part of payment k is Iₖ = Bₖ₋₁ · i, the principal part is Pₖ = M − Iₖ, and the remaining balance is Bₖ = Bₖ₋₁ − Pₖ. Total interest paid over the term is M · n − P.
The loan calculator computes the monthly payment on a loan with equal (annuity) payments — mortgage, consumer or business loan. The amortization schedule shows, for each payment, how much goes to interest and how much repays principal: at the start interest dominates, and over time the principal share grows. The early repayment simulation clearly shows how an extra payment today shortens the term and saves years of interest.
Note: the calculation assumes a fixed rate and equal payments. A real offer includes fees and insurance, reflected in the APR (annual percentage rate of charge).
Methodology
What the calculator computes
The calculator handles the most common loan type in Bulgaria — equal (annuity) monthly payments at a fixed rate. It returns three headline figures: the monthly payment, the total interest paid over the term, and the total amount paid. To these it adds a year-by-year amortisation schedule and an early repayment simulation.
Use it before signing a contract, to see the real cost of the loan in interest rather than only the monthly burden. Use it during the loan as well, to judge whether to direct spare funds towards early repayment or elsewhere.
The formula and the logic of the schedule
The monthly payment follows the annuity formula:
M = P · i · (1 + i)^n / ((1 + i)^n − 1)
- P — the loan amount (the principal you actually receive).
- i — the monthly interest rate, that is the annual rate divided by 12.
- n — the total number of monthly payments: the term in years times 12.
- M — the monthly payment, identical throughout the term.
The amortisation schedule follows from repeating three simple steps for each payment k:
- Interest part: I(k) = B(k−1) · i, that is interest on the previous month balance.
- Principal part: P(k) = M − I(k) — whatever is left of the payment after interest.
- New balance: B(k) = B(k−1) − P(k).
Because the balance falls every month, the interest part shrinks and the principal part grows, while the total payment stays put. Total interest over the term is M · n − P.
Worked example: a 150,000 € mortgage over 25 years
A loan of 150,000 €, an annual rate of 3.5%, a 25-year term.
- Monthly rate: i = 3.5% ÷ 12 = 0.2917% = 0.00291667.
- Number of payments: n = 25 × 12 = 300.
- (1 + i)^300 ≈ 2.395826.
- M = 150,000 × 0.00291667 × 2.395826 ÷ (2.395826 − 1) = 750.94 € per month.
Total paid: 750.94 × 300 = 225,280.61 €. Total interest: 75,280.61 € — more than half an extra principal, in interest alone.
The first payment splits as follows: interest 150,000 × 0.00291667 = 437.50 €, principal 750.94 − 437.50 = 313.44 €, new balance 149,686.56 €. The second payment already carries interest of 436.59 € and principal of 314.35 €. The difference between the two payments is about one euro — but over 300 months that difference compounds all the way through.
| End of year | Paid to date | Of which principal | Of which interest | Balance |
|---|---|---|---|---|
| 1 | 9,011 € | 3,822 € | 5,189 € | 146,178 € |
| 5 | 45,056 € | 20,519 € | 24,537 € | 129,481 € |
| 10 | 90,112 € | 44,957 € | 45,155 € | 105,043 € |
| 15 | 135,168 € | 74,060 € | 61,108 € | 75,940 € |
| 20 | 180,224 € | 108,721 € | 71,503 € | 41,279 € |
| 25 | 225,281 € | 150,000 € | 75,281 € | 0 € |
The table shows the effect that surprises most borrowers: after 10 years and over 90,000 € in payments, the balance has fallen only from 150,000 to about 105,000 €. Half of everything paid went to interest. The reverse is also true — by year 20, 71,503 € of the total 75,281 € of interest has already been paid, meaning 95% of the interest burden is carried in the first two thirds of the term.
Early repayment
If you add 150 € to every payment, paying 900.94 € instead of 750.94 €, the loan clears in about 229 months — 19 years and 1 month instead of 25 years. Interest saved is roughly 19,640 €. Note the disproportion: over 10 years the extra payments total 18,000 €, yet they save close to 20,000 € in interest, because every extra euro goes straight to principal and removes all the interest that principal would have generated to the end of the term.
This is exactly why early repayment is more effective the earlier it is made. The same 150 € a month, started in year 15, saves several times less.
In Bulgaria, early repayment of a mortgage is free of charge after the first year from drawdown. During the first year the bank may charge up to 1% of the amount repaid early. Consumer loans follow separate rules, with the fee capped depending on the remaining term. Check the specific terms in your contract before planning a large lump-sum repayment.
Practical guidance
Compare offers on the annual percentage rate of charge (APR), not on the interest rate. The APR includes valuation, approval and management fees, insurance and every other mandatory cost. Two offers with the same 3.5% rate can carry APRs of 3.7% and 4.3% — over 25 years on a 150,000 € loan the difference runs into tens of thousands of euros.
If the rate is variable and tied to a reference rate, also compute the payment 2 percentage points higher. In the example above, the payment at 5.5% is around 921 € — 170 € above the original. If that scenario breaks your budget, the term or the amount is too aggressive.
Do not forget the costs outside the loan: local property tax and waste collection fee, insurance, maintenance and building association charges. They do not appear in the amortisation schedule, but they do appear in the monthly budget.
Limitations of the calculation
The calculator assumes a fixed rate throughout the term and equal monthly payments with no grace period. It excludes fees, commissions and insurance, ignores early repayment charges, and does not support declining-payment schemes (equal principal), where the payment starts high and falls over time. The schedule is presented aggregated by year rather than by individual month. The early repayment simulation assumes the extra amount is paid every month without interruption, and that the bank shortens the term rather than the payment — if you choose to reduce the payment instead, the interest saved is considerably smaller.
Frequently asked questions
Why is almost the entire payment interest at the start?
Interest is charged each month on the current outstanding balance, which is largest at the beginning. On a 150,000 € loan at 3.5%, the first month of interest is 437.50 € out of a 750.94 € payment. As the balance falls, the interest part shrinks and the principal part grows, while the total payment stays the same. This is annuity mathematics, not a fee or a hidden condition.
How much does early repayment save?
It depends entirely on when you do it. On a 150,000 € loan over 25 years, an extra 150 € a month from the outset shortens the term by nearly 6 years and saves about 19,640 € in interest. The same amount started halfway through the term saves several times less, because the outstanding principal has already generated most of the interest.
Is there a charge for early repayment in Bulgaria?
For mortgages, the bank may charge up to 1% of the amount repaid during the first year from drawdown. After the first year, early repayment is free of charge. For consumer loans the fee is capped depending on the time remaining to maturity. Check the exact wording of your contract, as terms differ between banks and products.
What is the difference between the interest rate and the APR?
The interest rate reflects only the price of the borrowed money. The annual percentage rate of charge also includes every mandatory fee, commission and insurance premium tied to the loan, expressed as an annual percentage. That is why the APR is always higher than the rate, and why it is the only figure on which two offers can be compared fairly.
What changes if my rate is variable?
The amortisation schedule holds only while the rate stays unchanged. If the reference index moves, the bank recomputes the payment for the remaining term. A practical approach is to check the payment at a rate 2 percentage points higher — if it does not fit your budget, consider a smaller amount, a longer term or a fixed-rate period.
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The calculators are for guidance only and do not constitute financial, tax or legal advice. Parameters reflect 2026 legislation and should be verified annually. For a specific case, book a consultation with our specialists.