Why do I pay mostly interest at the start of my loan?

Interest is calculated on the remaining balance. Early in the loan the balance is high, so more of each payment goes to interest. As the balance decreases over time, more of each payment goes to principal.

How can I reduce total interest paid?

Making extra principal payments reduces the balance faster, which cuts the interest charged on future payments. Even small additional monthly amounts can save thousands and shorten the loan term significantly.

What is the difference between principal and interest?

Principal is the portion of your payment that reduces the loan balance. Interest is the cost of borrowing money, calculated as a percentage of the remaining balance.

Amortization Schedule Calculator — Full Payment Table

Full month-by-month breakdown — principal, interest, balance, equity milestones, and payoff optimizer.

Formula & Methodology

M = P × [ r(1 + r)ⁿ ] / [ (1 + r)ⁿ − 1 ]

Where:
M = Fixed monthly principal & interest payment
P = Loan principal (amount borrowed)
r = Monthly interest rate = annual rate ÷ 12
n = Total number of payments = term in years × 12

Each month's interest: I_k = B_k-1 × r
Each month's principal: P_k = M − I_k
Remaining balance: B_k = B_k-1 − P_k

This is the standard amortization formula used by virtually every lender. Each monthly payment is identical (fixed-rate loan), but the split between principal and interest changes every month. In month 1, nearly all of the payment is interest because the balance is high. By the final payment, almost nothing goes to interest — the balance is nearly zero.

The total interest paid equals the sum of all interest portions across all payments, or equivalently: (M × n) − P. This figure shows the true cost of borrowing.

About this calculation · Accuracy & Methodology

Key Terms Explained

Amortization: The process of paying off a debt through scheduled, equal periodic payments. Each payment covers both the interest accrued and a portion of the principal, gradually reducing the balance to zero.
Principal: The original amount borrowed. The portion of each monthly payment that reduces the principal is called the principal portion. Early payments have small principal portions; later payments have large ones.
Interest Portion: The cost of borrowing for that month, calculated as the remaining balance multiplied by the monthly interest rate. The interest portion decreases each month as the balance falls.
Remaining Balance: The amount still owed on the loan after each payment. Equals the previous balance minus the principal portion of the payment. Drops slowly at first, then accelerates toward the end of the loan.
Monthly Payment: The fixed amount paid each month for a standard fixed-rate loan. Determined by the loan amount, interest rate, and term. Does not change unless you make extra payments or refinance.
Total Interest: The sum of all interest charges across the life of the loan. Equals (Monthly Payment × Number of Payments) minus the original loan amount. A key metric for evaluating the true cost of a loan.
Extra Payment: Any amount paid above the required monthly payment, applied directly to principal. Extra payments reduce the balance faster, cut total interest, and shorten the loan term.
Payoff Date: The month and year of the final loan payment. Calculated from the start date plus the number of months in the schedule. Extra payments move this date earlier.
Interest Ratio: Total interest divided by the original loan amount. A ratio of 1.0× means you pay as much in interest as you borrowed. A 30-year loan at 7% has a ratio of roughly 1.4×.
Principal–Interest Crossover: The specific payment where the principal portion first exceeds the interest portion. Before this point your loan is interest-heavy; after it, each payment builds equity faster than it costs.

Real-World Examples

First-time buyer, 30-year mortgage at 6.75%

Loan: $350,000 Rate: 6.75% Term: 30 yrs

Payment: $2,270/mo

Total interest over 30 years: $467,200. In month 1, only $303 goes to principal. By month 300 (year 25), $2,126 goes to principal. Total paid: $817,200.

Refinancing to 15-year term saves huge

Loan: $280,000 Rate: 6.00% Term: 15 yrs

Payment: $2,363/mo

Total interest: $145,340 — less than half of a 30-year equivalent. Despite higher monthly payments, the 15-year saves $220,000+ in interest on a $280k loan.

$200/mo extra payment on 30-year loan

Loan: $400,000 Rate: 7.00% Extra: $200/mo

Saves ~$97,000

Adding $200/month to a $400k 30-year at 7% cuts the loan term by 5 years and 2 months, saving approximately $97,000 in total interest.

Rate & Term Comparison — $350,000 Loan

How rate and term affect monthly payment and total interest on a $350,000 loan:

Rate	15-Year Payment	15-Year Total Interest	30-Year Payment	30-Year Total Interest
5.50%	$2,859	$164,600	$1,987	$365,300
6.00%	$2,955	$181,900	$2,098	$405,300
6.50%	$3,051	$199,200	$2,212	$446,300
7.00%	$3,148	$216,600	$2,329	$488,400
7.50%	$3,247	$234,400	$2,449	$531,600
8.00%	$3,347	$252,500	$2,569	$574,800

Understanding Amortization: How Your Loan Really Works

Most people know their monthly mortgage payment but have never seen where the money actually goes. An amortization schedule pulls back the curtain, showing you exactly how your lender applies each dollar you pay. The math is elegant — and once you understand it, you can make smarter decisions about extra payments, refinancing, and loan terms.

The Front-Loaded Interest Problem

The most counterintuitive thing about amortized loans is how interest-heavy early payments are. On a $400,000 30-year mortgage at 7%, your monthly payment is $2,661. In month 1, $2,333 goes to interest and only $328 goes to principal. It's not until roughly year 21 that the split crosses 50/50.

This isn't the bank tricking you — it's pure math. Interest is charged on the outstanding balance, and at the start your balance is $400,000. Month 1 interest = $400,000 × (0.07 ÷ 12) = $2,333. As the balance slowly decreases, so does the interest charge. The payment stays constant, so more and more of it goes to principal over time.

Why the Extra Payment Strategy Is So Powerful

Because every dollar of principal you pay reduces the base on which future interest is calculated, extra payments create a compounding benefit. Pay $200 extra in month 1, and you don't just eliminate month 1's $200 principal payment — you shift the entire schedule forward, eliminating all the interest that would have accrued on that $200 for the remaining life of the loan.

15-Year vs. 30-Year: The Real Numbers

The 30-year mortgage offers a lower monthly payment, making it accessible to more buyers. But the amortization schedule reveals the cost. On a $400,000 loan at 6.5%, a 30-year mortgage costs $252,000 more in interest than a 15-year mortgage. The 15-year schedule moves through the interest-heavy phase twice as fast, meaning you build equity rapidly.

Using the Schedule to Plan Refinancing

When you refinance, you reset the amortization clock. If you're 10 years into a 30-year mortgage and you refinance into a new 30-year loan — even at a lower rate — you're now paying 40 years total. The amortization schedule helps you evaluate this: compare the total remaining interest on your current schedule versus the total interest on the new loan.

When to Consult a Professional

This calculator provides accurate amortization math for standard fixed-rate loans. Adjustable-rate mortgages (ARMs), interest-only loans, balloon payments, and loans with prepayment penalties involve additional factors that require professional analysis.

Frequently Asked Questions

What is an amortization schedule?

An amortization schedule is a complete table of every periodic loan payment, showing exactly how much of each payment goes to principal and how much goes to interest, along with the remaining balance after each payment.

Why do I pay mostly interest at the beginning of my loan?

Interest is calculated as a percentage of the remaining balance. At the start, the balance is at its highest, so the interest charge is at its largest. As you make payments, the balance decreases — and so does the interest portion.

How much can extra payments really save?

On a $350,000 30-year mortgage at 7%, adding just $200 per month cuts over 5 years off the loan and saves around $100,000 in interest. Use the Extra Payment field to see the exact savings for your specific loan.

Does making extra payments reduce my monthly payment amount?

No — for a standard fixed-rate loan, extra payments reduce the loan balance and shorten the term, but they do not reduce the required monthly payment. The required payment stays the same until the loan is paid off early.

What is negative amortization?

Negative amortization occurs when a loan payment is less than the interest accrued for that period. Instead of decreasing, the balance actually grows. Standard fixed-rate mortgages do not have negative amortization.

Is my mortgage payment the same as what's on the amortization schedule?

The amortization schedule shows only the principal and interest portion of your payment. Your actual monthly mortgage payment also includes property taxes, homeowner's insurance, and possibly PMI — these escrow items are added on top by your lender.

How do I read the amortization table?

Each row represents one month (or one year in Yearly View). The columns show: payment number, date, total payment, principal portion (cyan), interest portion (pink), remaining balance, and cumulative equity percentage.

Can I use this for auto loans and personal loans?

Yes. The amortization formula applies to any fixed-rate installment loan — mortgages, auto loans, personal loans, student loans. Just enter the loan amount, interest rate, and term in years (e.g., a 60-month auto loan is 5 years).

What happens if I pay off my loan early?

If you pay off the loan early, you pay only the remaining balance plus any accrued interest through the payoff date — you do not owe all the future interest shown in the schedule. Some loans include a prepayment penalty, so check your loan agreement.

What is the difference between simple interest and amortized interest?

Simple interest is calculated only on the original principal. Amortized interest is recalculated each month on the remaining balance, which decreases over time. Most mortgages use amortized interest.

Amortization Schedule Calculator

Full Amortization Schedule

Rate Scenarios

Rate × Term Sensitivity Matrix

Extra Payment Impact

15-Year vs 30-Year Comparison

⚡ Bi-Weekly Payment Strategy

🎯 Payoff Goal Seeker

🏠 Equity Milestones

📈 Extra Payment Projection

💵 One-Time Lump Sum Analyzer