Amortization Calculator (VND)
If you take out a loan in Vietnam — most often a mortgage on an apartment — the bank will usually quote a level monthly payment that stays the same for the whole term. What is not obvious is that the split inside that payment shifts every single month. Early on, when the outstanding balance is large, most of your payment is interest and only a sliver pays down the loan itself. As the balance falls, the interest portion shrinks and the principal portion grows. This gradual unwinding is called amortization, and the month-by-month table of principal, interest and remaining balance is your amortization schedule.
Reading that schedule answers questions a single "monthly payment" number cannot. On a 2.000.000.000 VND loan at an illustrative 9%/year over 180 months, the fixed payment is 20.285.332 VND — yet in month one 15.000.000 VND of that is interest and only 5.285.332 VND reduces the balance. Halfway through the term (after month 90) you still owe 1.324.117.098 VND — well over half the original loan — because principal repays so slowly at first. And over the full term you will pay 1.651.359.703 VND in interest on top of the 2.000.000.000 VND you borrowed.
The calculator above takes your loan amount, annual rate and term in months, and returns the monthly payment, total interest and total of all payments, plus the first month's interest so you can see the principal-to-interest ratio at a glance. One caveat specific to Vietnam: the rate in every example here is an illustrative assumption, not a quote. Vietnamese mortgage rates typically offer a fixed promotional rate for the first year or two, then float as a reference rate plus a margin. Enter the rate from your own contract, and re-run the schedule at a higher post-promo rate to stress-test the worst case.
How the schedule is built
The level-payment formula
A fully-amortizing loan is repaid with an identical payment each month:
M = P × r / (1 − (1 + r)^(−n))
| Symbol | Meaning |
|---|---|
| M | Fixed monthly payment |
| P | Original loan amount (opening balance) |
| r | Monthly rate = annual rate ÷ 12, as a decimal |
| n | Total number of monthly payments |
The calculator derives the monthly rate as annual rate ÷ 12, the convention Vietnamese banks use for reducing-balance loans. So 9%/year becomes r = 0.09 ÷ 12 = 0.0075 per month.
Splitting each payment
For every month the tool runs the same three steps:
- Interest this month = opening balance × r.
- Principal this month = M − interest this month.
- New balance = opening balance − principal this month.
Because M is constant while the balance falls, interest declines and the principal share rises each month. On the 2.000.000.000 VND / 9% / 180-month example, year 1 repays only 66.106.742 VND of principal against 177.317.238 VND of interest, whereas year 15 repays 231.960.996 VND of principal against just 11.462.984 VND of interest.
Totals
- Total of payments = M × n.
- Total interest = (M × n) − P.
Here the total of payments is 3.651.359.703 VND; subtract the 2.000.000.000 VND borrowed and the interest bill is 1.651.359.703 VND. The longer the term, the more this number balloons — which is why extending a term to lower the monthly payment is rarely free.
What the model omits
It assumes a constant rate for the entire term, and ignores appraisal fees, loan insurance and early-repayment penalties (many Vietnamese contracts charge 1–3% of the amount prepaid during the first few years). Since real VND rates usually float after the promotional window, treat the schedule as a reference scenario and reconcile it with your contract.
Worked example: a 2.000.000.000 VND loan at an illustrative 9%/year over 180 months (15 years)
Illustrative assumptions: a constant 9%/year rate, reducing-balance repayment, no fees or prepayment penalty. The fixed payment is 20.285.332 VND/month.
| Point in the loan | Principal in period | Interest in period | Balance at period end |
|---|---|---|---|
| Month 1 | 5.285.332 | 15.000.000 | 1.994.714.668 |
| After month 90 (halfway) | — | — | 1.324.117.098 |
| Year 1 (sum) | 66.106.742 | 177.317.238 | 1.933.893.258 |
| Year 15 (sum) | 231.960.996 | 11.462.984 | 0 |
The front-loading of interest is stark. Across the first five years the loan accrues 818.478.320 VND of interest; across the last five years only 239.907.041 VND — even though the monthly payment never changed. Nothing happened except the balance shrank, so there was less left to charge interest on.
Why this matters for your decisions
Two practical takeaways fall straight out of the table:
- Selling or refinancing early is expensive in interest terms. If you exit this loan at the halfway mark you have paid 90 payments totalling 1.825.679.851 VND but still owe 1.324.117.098 VND of the original 2.000.000.000 VND — most of what you paid went to the bank as interest, not into equity.
- Extra principal is most powerful early. A dong of principal repaid in year 1 cancels interest on that dong for up to 168 remaining months; the same dong in year 14 cancels almost nothing. If your contract allows penalty-free overpayments, front-load them.
Remember the 9% rate is a modelling assumption. Re-run the calculator with your actual contract rate, and a higher floating rate too — at a 15-year horizon even a one-point increase adds millions of dong to the interest total.
Frequently asked questions
What is an amortization schedule?
It is a month-by-month table for a level-payment loan showing how each payment splits into principal and interest, plus the remaining balance. The payment stays constant, but early on it is mostly interest and very little principal; later the mix reverses. On a 2.000.000.000 VND loan at an illustrative 9%/year over 180 months, the 20.285.332 VND payment in month one is 15.000.000 VND interest and only 5.285.332 VND principal.
What is the formula for the monthly payment?
M = P × r / (1 − (1 + r)^(−n)), where P is the loan amount, r the monthly rate (annual rate ÷ 12, as a decimal) and n the number of months. Verifiable example: P = 2.000.000.000 VND, r = 0.09 ÷ 12, n = 180 gives M = 20.285.332 VND/month. Each month, interest = balance × r and principal = M − interest, so as the balance falls the principal portion grows.
Why is so much of an early payment interest?
Because interest each month is charged on the outstanding balance, which is near its peak at the start. On the 2.000.000.000 VND / 9% / 180-month example, year 1 repays just 66.106.742 VND of principal against 177.317.238 VND of interest. By year 15 it flips: 231.960.996 VND of principal against only 11.462.984 VND of interest. The schedule is "front-loaded" with interest.
How much total interest will I pay over the loan?
Total interest = (monthly payment × number of months) − loan amount. For the 2.000.000.000 VND loan at an illustrative 9%/year over 180 months: total of payments is 3.651.359.703 VND, so interest is 1.651.359.703 VND on top of the 2.000.000.000 VND borrowed. This is exactly why a longer term — which lowers the monthly payment — usually raises the lifetime interest bill substantially.
How much do I still owe halfway through the term?
More than half, because principal repays slowly early on. On the 2.000.000.000 VND loan at an illustrative 9%/year over 180 months, after month 90 (the halfway point) you still owe 1.324.117.098 VND — roughly 66% of the original amount. Most of what you paid in the first half went to the bank as interest, not into your equity.
Do Vietnamese mortgage rates stay fixed for the whole term?
Usually not. Most VND home loans offer a fixed promotional rate for the first one or two years, then float as a reference rate plus a margin, reset periodically. This calculator assumes a constant rate so the math is verifiable, but you should run it once at the promo rate and once at a higher expected floating rate. The interest total and monthly payment can both rise materially when the rate resets.
Is it worth paying extra principal each month?
Often yes, because extra payments go straight to the balance and erase the future interest on it. On the VI example (1.000.000.000 VND at 10% over 240 months), adding 5.000.000 VND/month clears the loan in 102 months instead of 240 and cuts interest by 830.981.454 VND. The earlier you overpay, the bigger the saving — but check your contract for early-repayment penalties first.