Amortization Calculator: Schedule & Payoff

Amortization Calculator: Complete 2026 Loan Payoff & Interest Savings Guide

Free amortization calculator with month-by-month payment schedules. How to calculate mortgage payment and amortization formula. Extra payment modeling, bi-weekly acceleration. No sign-up, all calculations run locally.

What This Calculator Does

The amortization calculator generates a month-by-month payment schedule for any fixed-rate loan, showing exactly how each payment splits between principal and interest. It helps homeowners, borrowers, and financial planners see the true cost of a loan over time, model extra payment strategies, and identify when the principal tipping point occurs, the month your principal portion first exceeds interest. Enter a loan amount, interest rate, and term to produce the full schedule. Optionally add recurring extra monthly payments or a one-time lump sum to see how accelerated payoff reduces total interest and shortens the term.

Who it helps:

Homebuyers evaluating mortgage costs, borrowers comparing loan terms, and anyone modeling extra-payment strategies to build equity faster.
Key outputs:

Monthly payment amount, month-by-month principal/interest split, total interest paid, principal tipping point, and the impact of extra payments on payoff timeline.
What it does NOT do:

Does not calculate taxes, insurance, or PMI. Does not support adjustable-rate, interest-only, or balloon loan structures. For full PITI estimates, use a mortgage calculator.

How to Use This Calculator

Enter the total loan amount (principal) in the first field, this is the amount you are borrowing, not the purchase price. Input the annual interest rate as a percentage (e.g., 6.5 for 6.5%). Select a loan term in years; common choices are 15 or 30 years for mortgages, though any term works. If you want to model accelerated payoff, enter an extra monthly payment amount or a one-time lump sum in the optional fields. The calculator instantly produces a full amortization table showing each month's payment number, principal portion, interest portion, and remaining balance. The summary panel displays total interest paid over the life of the loan, the month when principal first exceeds interest (the tipping point), and, if extra payments are entered, how many months are saved and how much interest is avoided compared to the standard schedule.

How Loan Amortization Works: Complete Formula Guide

The Amortization Formula Explained

Amortization calculates fixed payments that fully repay a loan over a set term. Each payment covers that month's interest plus a portion of principal. The formula ensures the loan reaches zero at the final payment.

Monthly Payment Formula:

$M = P \times \frac{i(1+i)^n}{(1+i)^n - 1}$
where M = monthly payment, P = principal (loan amount), i = monthly interest rate (annual rate ÷ 12), n = total number of payments (years × 12)
Example Calculation:

$400,000 loan at 6.5% for 30 years: i = 0.065 ÷ 12 = 0.005417, n = 360 payments. M = $400,000 × [0.005417(1.005417)³⁶⁰] / [(1.005417)³⁶⁰ – 1] = $2,528.27/month.
Interest Portion Formula:

$\text{Interest}_{\text{month}} = \text{Balance} \times i$
Each month's interest is calculated on the current remaining balance. As balance decreases, interest decreases and more payment goes to principal
Principal Portion Formula:

$\text{Principal}_{\text{month}} = M - \text{Interest}_{\text{month}}$
Whatever remains after interest is applied to principal reduction. This is why the principal portion grows over time as interest shrinks
Scope & Limits:

Standard amortization formulas for fixed-rate loans. Extra payment modeling assumes principal-only application. All calculations run in your browser; no data is sent to servers. Verify with a qualified professional before making significant mortgage or loan decisions.

Understanding the Payment Split Over Time

The amortization schedule reveals how each payment is allocated between principal and interest throughout the loan term.

Year 1 Payment Allocation ($400K at 6.5%):

Monthly payment: $2,528. First payment: $2,167 interest (86%) + $361 principal (14%). After 12 payments, you've paid $30,339 but only reduced principal by $4,449. The lender received $25,890 in interest.
Year 15 Payment Allocation:

Same $2,528 payment, but now: $1,264 interest (50%) + $1,264 principal (50%). You've reached the "tipping point" where principal and interest are equal.
Year 30 Payment Allocation:

Final payment: $14 interest (0.5%) + $2,514 principal (99.5%). Nearly all of your payment now builds equity. Total interest paid over 30 years: $510,177 on a $400,000 loan.

Extra Payment Strategies: Detailed Savings Analysis

Extra Monthly Payments: Impact Calculator

Consistent extra monthly payments compound their effect over time. Here's the exact impact on a $400,000 loan at 6.5% for 30 years (standard total interest: $510,177).

+$100/month Extra:

Total interest: $465,000 (saves $45,000). Payoff: 25.5 years (saves 4.5 years). Effective return: 6.5% guaranteed on every extra dollar.
+$200/month Extra:

Total interest: $428,000 (saves $82,000). Payoff: 22.3 years (saves 7.7 years). Monthly cash flow increase after payoff: $2,728 ($2,528 + $200 you were paying extra).
+$500/month Extra:

Total interest: $340,000 (saves $170,000). Payoff: 16.8 years (saves 13.2 years). You'll own your home free and clear in half the original term.
Key Insight:

Extra payments must be applied to principal only, not "future payments." Some lenders apply extra payments incorrectly, verify your statement shows principal reduction, not advance payment credit.

Lump Sum Payment Timing Analysis

One-time lump sum payments have dramatically different impacts depending on when they're made. Here's the same $10,000 payment at different points.

$10,000 in Year 1:

Interest saved: $24,800. Time saved: 14 months. Every dollar saves $2.48 in future interest because it stops compounding for 29 years.
$10,000 in Year 10:

Interest saved: $12,100. Time saved: 11 months. Still valuable, but only 20 years of compound prevention remain.
$10,000 in Year 20:

Interest saved: $4,200. Time saved: 8 months. Only 10 years of interest savings, and the balance is already much lower.
Strategic Timing:

If choosing between paying $10,000 in year 1 vs. investing it, your mortgage rate is the guaranteed return rate. At 6.5%, you'd need consistent 6.5%+ investment returns to beat the mortgage paydown.

Bi-Weekly Payment Mathematics

Bi-weekly payments are popular but often misunderstood. Here's exactly how they work and whether you should use them.

The Math:

26 bi-weekly payments ÷ 2 = 13 monthly payment equivalents per year. You're making one extra full payment annually. On a $2,528 payment, that's $2,528 extra principal per year.
Savings on $400K at 6.5%:

Total interest: $420,000 (saves $90,000). Payoff: 24.6 years (saves 5.4 years). Equivalent to paying $211 extra monthly ($2,528 ÷ 12).
DIY Alternative:

Add 1/12 of your payment ($211 on a $2,528 payment) to each monthly payment. Achieves identical results without bi-weekly program fees. Some banks charge $300-$500 for bi-weekly "enrollment."
Cash Flow Consideration:

Bi-weekly means 26 payments per year vs. 12 monthly. Two months per year will have 3 payment withdrawals instead of 2. Ensure your budget can handle the irregular cash flow.

Loan Term Comparison: 15 vs. 20 vs. 30 Year Analysis

Term Length Trade-Offs on a $400,000 Loan at Current Rates

Shorter terms have lower rates and dramatically less total interest, but higher monthly payments. Here's the complete comparison.

30-Year Fixed (6.5% rate):

Monthly payment: $2,528. Total interest: $510,177. Total paid: $910,177. Best for: maximizing cash flow, investing the difference, uncertain income.
20-Year Fixed (6.25% rate):

Monthly payment: $2,922 (+$394/month). Total interest: $301,280. Total paid: $701,280. Saves $208,897 vs. 30-year. Best for: balanced approach, stable income.
15-Year Fixed (5.875% rate):

Monthly payment: $3,349 (+$821/month). Total interest: $202,820. Total paid: $602,820. Saves $307,357 vs. 30-year. Best for: high earners, aggressive wealth building.
The Hidden Benefit:

15 and 20-year loans typically have rates 0.25-0.75% lower than 30-year loans. This rate difference compounds the savings beyond just the shorter term.

PMI Elimination: Complete Strategy Guide

PMI Thresholds and Cancellation Rules

Private Mortgage Insurance protects the lender (not you) when your down payment is below 20%. Understanding the rules helps you eliminate it faster.

Automatic Termination (78% LTV):

PMI automatically cancels when your loan balance reaches 78% of the original purchase price, based on the original amortization schedule. No action required, but this may take 10-11 years on a 30-year loan.
Borrower-Requested Cancellation (80% LTV):

You can request cancellation at 80% LTV through principal paydown. You must be current on payments with good payment history. Some lenders require written request; others have online forms.
Appraisal-Based Cancellation:

If your home has appreciated significantly, a new appraisal can establish higher value, lowering your LTV. If original LTV was 90%+, you typically need 75% current LTV. Appraisals cost $400-$600.
PMI Cost Impact:

PMI typically costs 0.5-1% of loan amount annually. On $400,000: $2,000-$4,000/year ($167-$333/month). Eliminating PMI 5 years early saves $10,000-$20,000. Factor this into your extra payment strategy.

FAQ

What is loan amortization?

Amortization is the process of paying off a loan through fixed monthly payments that cover both principal and interest. Each payment stays the same, but the split changes over time: early payments are mostly interest (because the balance is highest), while later payments are mostly principal as the balance decreases.

How do I calculate my monthly mortgage payment?

Use the formula: M = P × [i(1+i)^n] / [(1+i)^n – 1], where M = monthly payment, P = loan principal, i = monthly interest rate (annual rate ÷ 12), and n = total number of payments. For a $400,000 loan at 6.5% for 30 years: i = 0.065/12 = 0.00542, n = 360, M = $2,528/month.

What is the principal tipping point?

The tipping point is when your monthly principal payment first exceeds your interest payment. For a 30-year mortgage at 6.5%, this occurs around year 10-12. Before this point, most of your payment benefits the lender; after, most builds your equity. Understanding this helps explain why early extra payments are so powerful.

How much can I save with extra principal payments?

On a $400,000 loan at 6.5% for 30 years: Extra $100/month saves ~$45,000 and cuts 4-5 years. Extra $200/month saves ~$75,000 and cuts 7-8 years. A $10,000 lump sum in year 1 saves ~$25,000 in interest. Earlier payments save more because they reduce the balance that accrues interest for longer.

Should I pay down my mortgage or invest?

Compare your mortgage rate to expected investment returns. If your rate exceeds 6-7%, paying down principal is a guaranteed return at that rate. If rates are lower (3-4%), investing in diversified funds (historically 7-10% returns) may yield more over time. Consider risk tolerance: mortgage payoff is guaranteed; investment returns are not.

When can I cancel PMI on my mortgage?

PMI automatically cancels at 78% loan-to-value (LTV) based on the original schedule. You can request early cancellation at 80% LTV through principal paydown or home appreciation (may require appraisal). On a $400,000 home with 10% down, reaching 80% LTV saves $150-$300/month in PMI costs.

Amortization Calculator: Interest-Efficiency Model

Loan terms

Early payoff

Principal tipping point

Interest vs. principal

Amortization schedule

Amortization Strategy: Winning the Long Game Against Interest

Strategic Amortization Insights

The Front-Loading Wealth Transfer

The $1 Early vs. $1 Late Multiplier

The Bi-Weekly Illusion

The Refinance Break-Even Trap