Amortization with fixed instalments

Banks show you one monthly number - the amortization schedule shows where every dollar goes

A $300,000 mortgage at 7% for 25 years carries a fixed payment of $2,120. That number stays constant for 300 months. What changes - dramatically - is the split between principal and interest inside each payment. In month one, $1,750 goes to interest and only $370 reduces your debt. It takes roughly 17 years before principal exceeds interest in a single payment. This calculator generates the full yearly schedule so you can see exactly where your money lands.

Interest in 1st year (fixed, $300k/7%/25y)

$20,816

82% of year-one payments

Interest in last year

$871

3.4% of year-25 payments

How to use this calculator - step by step

Loan amount - enter the net principal. For a $350,000 house with 20% down, that is $280,000.
Annual interest rate - the nominal rate from your lender. Check whether it is fixed or variable.
Repayment period - in years. A shorter term increases payments but drastically reduces total interest.
Instalment type - fixed keeps the payment constant; declining keeps the principal portion constant and reduces interest faster.
Read the schedule - the table shows principal repaid, interest paid and remaining balance for every year of the loan.

Sample amortization - $300,000 at 7% for 25 years (fixed)

How the principal/interest split shifts over time:

Year	Principal repaid	Interest paid	Remaining balance
1	$4,624	$20,816	$295,376
5	$6,337	$19,103	$272,230
10	$9,046	$16,394	$234,199
15	$12,914	$12,526	$179,375
20	$18,432	$7,008	$100,684
25	$24,569	$871	$0

Practical examples

$200,000 at 6% for 30 years, fixed - monthly payment: $1,199. Year-1 principal: $2,421. Year-1 interest: $11,947. After 10 years, remaining balance: $167,371 (you have repaid only 16% of the loan in a decade).

$200,000 at 6% for 30 years, declining - first payment: $1,556, last: $558. Year-1 principal: $6,667 (constant). Year-1 interest: $11,650. Total interest savings vs fixed: $51,176.

$50,000 personal loan at 9% for 5 years, fixed - monthly payment: $1,038. Year-1 principal: $8,009. Year-1 interest: $4,447. By year 3, principal already dominates each payment.

$500,000 at 6.5% for 30 years, fixed - monthly payment: $3,160. Total interest: $637,684. Multiplier: 2.28x - you repay more than double the borrowed amount.

$100,000 at 5% for 15 years, fixed - monthly payment: $791. Total interest: $42,343. Same loan at 30 years: payment drops to $537 but interest nearly triples to $93,256.

FAQ - Frequently asked questions

Why does most of my early payment go to interest?

Interest is calculated on the remaining balance. Early in the loan, the balance is near maximum, so the monthly interest charge is high. As you pay down principal, the interest portion shrinks and the principal portion grows. On a $300,000 / 7% / 25-year fixed mortgage, the crossover point - where principal exceeds interest - occurs around year 17.

How much of my loan have I repaid after 5 years?

Less than you think. On a $300,000 / 7% / 25-year fixed mortgage, after 5 years you have made $127,200 in total payments but reduced the balance by only $27,770. The remaining $99,430 went to interest. After 5 years, you still owe $272,230 - about 91% of the original loan.

Fixed or declining - which reduces total interest more?

Declining instalments always produce less total interest because the principal is repaid at a constant, faster rate. On a $300,000 / 7% / 25-year loan, declining saves $72,726 in interest. The trade-off: the first payment is $2,750 instead of $2,120. If your budget can absorb the higher initial cost, declining is the cheaper option over the full term.

How does shortening the term affect the schedule?

Dramatically. A $300,000 loan at 7%: at 30 years, the monthly payment is $1,996 and total interest is $418,527. At 15 years, the payment rises to $2,696 (+$700) but total interest drops to $185,367. That extra $700/month saves you $233,160 and 15 years of payments.

Can I use this for a car loan or personal loan?

Yes. The amortization math is the same regardless of loan type. Enter the principal, annual rate and term. Car loans typically run 3-7 years at 6-14%. Personal loans: 1-7 years at 6-18%. Because these terms are shorter, the principal/interest crossover happens much sooner - often within the first 1-2 years.

Does overpaying change the amortization schedule?

Yes, significantly. Every overpayment reduces the remaining balance, which lowers the interest in all subsequent payments. On a $300,000 / 7% / 25-year fixed mortgage, adding $200/month in overpayments shortens the loan by about 5 years and saves roughly $76,000 in interest. This calculator shows the standard schedule; to model overpayments, reduce the loan amount or shorten the term.

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