Amortization Calculator

An amortization calculator splits every fixed loan payment into its interest and principal parts and shows the remaining balance after each one. Example: on a $250,000 loan at 6.5% for 30 years, the payment is $1,580 a month - the first payment is $1,354 interest and only $226 principal, and lifetime interest totals about $318,861.

This page is the schedule tool - it answers "how does each payment split, and when is the loan gone?" To estimate a full house payment with taxes, insurance and PMI, use the mortgage calculator; to quickly size a payment for any fixed-rate loan without the year-by-year table, use the loan calculator; and to plan extra or lump-sum payments against an existing mortgage, use the mortgage payoff calculator.

The amortization formula

Every fully amortizing fixed-rate loan uses the same payment formula:

where P is the loan amount (principal), r is the monthly interest rate (annual APR ÷ 12), and n is the total number of payments (years × 12). The result M is the single fixed payment that pays the loan to exactly zero over the term. Each month the calculator charges interest equal to balance × r, applies the rest of the payment to principal, and carries the new balance forward.

How to read an amortization table

An amortization schedule (or amortization table) lists each period and splits the payment into principal and interest, then shows the remaining balance. Early rows are interest-heavy because interest is charged on the large opening balance. As the balance shrinks, the interest charge falls and the principal portion grows - so the loan pays down slowly at first and accelerates near the end. This calculator groups the months into yearly totals to keep the table readable while still showing the full picture.

Amortization schedule example: $300,000 at 6.5% for 30 years, first 12 months

Here is exactly what the first year of a real schedule looks like. The fixed payment is $1,896.20 per month; every value below is computed with the standard formula.

After twelve payments totaling $22,754, the balance has fallen by only $3,353 - about 85% of the first year goes to interest. Over the full 30-year term this loan costs $382,633 in interest on top of the $300,000 borrowed.

Why extra payments save so much

Because interest is always charged on the outstanding balance, every dollar you pay above the required payment removes principal that would otherwise accrue interest for the rest of the loan. On the $250,000 example above, adding just $200 per month shaves roughly 8 years off the term and saves tens of thousands in interest. Enter an extra monthly amount and the calculator reports the exact interest saved and months saved for your numbers.

Works for any fixed-rate loan

• Mortgages: 30-, 20- or 15-year home loans amortize on this exact formula.
• Auto loans: typically 3-7 year terms; the schedule shows how quickly you build equity.
• Personal & student loans: same math, usually shorter terms and higher rates.
• Comparison: change the term to compare total interest between, say, a 15- and 30-year loan.

How to use this amortization calculator

You only need three numbers to build a full schedule. Work through the fields in order:

1. Loan amount: enter the principal you are borrowing - the price minus any down payment for a mortgage or auto loan, or the full balance for a personal or student loan.
2. Interest rate (APR): use the rate your lender quoted. The calculator converts it to a monthly rate by dividing by 12, so enter the annual figure, not a monthly one.
3. Loan term: set the number of years. Switching between, say, 15 and 30 years instantly shows how the payment and total interest move in opposite directions.
4. Extra payment (optional): add a recurring monthly amount above the required payment to see how much interest and time you save.

The result updates immediately. Read the monthly payment and total interest at the top, then scan the year-by-year table to watch the balance fall and the principal/interest split flip over the life of the loan.

Who this calculator is for

Anyone with a fixed-rate loan can use it to understand what they are really paying. It is especially useful for:

• Home buyers who want to see the principal/interest breakdown behind a mortgage quote before they sign.
• Car shoppers comparing a 48-month versus a 72-month auto loan and the extra interest a longer term costs.
• Borrowers paying down debt who want to know exactly how much an extra $50 or $200 a month would save.
• Students and graduates mapping out a repayment plan and the true lifetime cost of a loan.
• Anyone comparing offers who needs an apples-to-apples view of total interest, not just the monthly figure.

A second worked example: a 5-year auto loan

Suppose you finance $30,000 for a car at 7% APR over 5 years (60 months). The fixed monthly payment is about $594. In the first month roughly $175 is interest and $419 reduces the balance - already a much healthier split than a 30-year mortgage, because the short term forces the principal down fast. Over the full loan you pay about $5,645 in total interest. Stretch the same loan to 7 years and the monthly payment drops to about $453, which looks easier, but total interest climbs to roughly $8,034 - nearly $2,400 more for the same car. This is the trade-off the schedule makes visible: a lower payment almost always means more interest paid over time. For a car deal that also folds in sales tax and a trade-in, the auto loan calculator runs the same amortization on the financed total.

Key amortization terms explained

• Principal: the amount you actually borrowed and still owe. Each payment reduces it; interest is always calculated on the current principal.
• Interest: the lender's charge for borrowing, equal to the remaining balance times the monthly rate. It is largest at the start and shrinks as you pay down.
• Term: the length of the loan in months or years. It sets how many payments you make and how steep the payoff curve is.
• Amortization: the process of spreading a loan into equal payments that fully retire it by the end of the term.
• Balance: the principal still outstanding after each payment. When it hits zero, the loan is paid off.
• Total of payments: every payment added together (principal plus all interest) - the real lifetime cost of the loan.

What changes the result the most

Adjust the inputs and a few levers clearly dominate the payment and the total interest:

• Loan amount: the biggest driver of both the monthly payment and total interest - borrow less and everything falls.
• Interest rate: on a long term, even half a percent meaningfully changes the payment and adds up to thousands over the life of the loan.
• Term length: a shorter term raises the monthly payment but slashes total interest; a longer term does the reverse.
• Extra payments: any amount above the required payment attacks principal directly and compounds in your favor for the rest of the loan.

How much interest does the loan term add? $300,000 at 6.5% compared

Same loan amount, same rate - only the term changes. Every row is computed with the amortization formula; note how the first month's principal collapses as the term stretches.

Going from 15 to 30 years lowers the payment by $717 a month but adds $212,235 of interest - the 30-year loan pays more in interest than the entire amount borrowed.

How the schedule is used in real life

An amortization schedule is more than a curiosity. Lenders use it to set your fixed payment and to track exactly how much principal you have repaid - which determines your equity in a home or car and when private mortgage insurance can be removed. Borrowers use it to decide whether to make extra payments, to estimate the payoff balance if they sell or refinance, and to compare two loan offers on total interest rather than just the headline payment. Accountants and the IRS rely on the interest portion of the schedule because mortgage and student-loan interest can be tax-deductible, while the principal portion is not. Seeing the split in advance helps you plan all of these decisions with real numbers.

Limitations and assumptions

This calculator is a planning estimate, not a loan document. Keep these assumptions in mind:

• It assumes a single fixed interest rate for the entire term and does not model variable or adjustable rates.
• It uses monthly compounding; a lender using a daily day-count convention may show slightly different interest.
• It excludes lender fees, points, taxes, insurance and escrow, so your actual monthly bill can be higher than the principal-and-interest figure shown.
• It assumes on-time, equal payments with no late fees, payment holidays, balloon payments or interest-only periods.
• Results are estimates - use your lender's official amortization schedule for the exact figures on your loan.

How it compares to related calculators

This page answers "how does my loan pay down, period by period?" If your question is different, a sister tool fits better:

• To estimate a home payment with taxes, insurance and PMI, use the Mortgage Calculator.
• To see how extra or one-time payments shorten a mortgage, use the Mortgage Payoff Calculator.
• To size a general fixed-rate payment quickly, use the Loan Calculator.
• To compare simple and compound interest on savings or debt, use the Interest Calculator.
• To finance a car specifically, the Auto Loan Calculator adds sales tax, trade-in and fees to the same amortization math.

The crossover point: when principal overtakes interest

One of the most revealing features of any amortization schedule is the crossover point - the payment at which the principal portion finally exceeds the interest portion. Before this point, more than half of every payment is going to the lender as interest; after it, the majority is reducing what you owe. On a 30-year mortgage at typical rates, this crossover often does not arrive until somewhere between year 15 and year 20, which surprises most borrowers. It means that for the entire first half of a long loan, you are paying down principal more slowly than the headline payment suggests. A shorter term or a lower rate pulls the crossover point much earlier; on a 15-year loan it can arrive within the first few years. Watching the year-by-year table, you can spot the exact year your principal contribution overtakes interest, which is also roughly when your equity in the asset starts to build in earnest.

When does principal exceed interest? Crossover point by rate and term

Computed for a $300,000 loan: the table shows the first payment in which the principal portion is larger than the interest portion. The rate matters far more than most borrowers expect.

At 6.5% on a 30-year loan, the majority of your payment keeps going to interest until month 233 - almost 20 years in. The same loan on a 15-year term crosses over in year 5. The crossover month does not depend on the loan amount, only on the rate and term, so these months apply to any loan size.

Strategies to pay less interest over the life of the loan

Because the schedule charges interest on the remaining balance every month, the most effective way to cut your lifetime interest is to shrink that balance faster than the contract requires. Several practical strategies all work through the same mechanism:

• Add a fixed amount to every payment. Even a round number like $100 or $200 a month, applied straight to principal, compounds in your favor for the remaining term. The earlier in the loan you start, the bigger the effect, because that principal would otherwise have accrued interest for the longest time.
• Make one extra payment a year. A lump sum from a tax refund or bonus, or the biweekly trick that produces a 13th payment annually, can remove years from a long loan without changing your monthly budget much.
• Round up the payment. Rounding a $1,580 payment up to $1,700 quietly sends $120 to principal every month and barely registers in your finances, yet it can save a meaningful chunk of total interest.
• Choose a shorter term up front. If you can afford the higher payment, a 15-year term instead of a 30-year one carries a lower rate and dramatically less interest, because the balance is forced down on a steeper curve from day one.
• Refinance to a lower rate - carefully. A lower rate reduces the interest charged on the balance, but starting a fresh 30-year term resets you to the interest-heavy early payments. Refinancing saves money only if you keep the term short or keep paying extra principal.

Whatever method you choose, confirm the extra money is applied to principal and not held as a prepayment of the next bill, and check that your loan has no prepayment penalty. Enter your own numbers and an extra monthly amount above to see precisely how each strategy translates into interest saved and months shaved off your specific loan.

Fixed-payment amortization vs. other repayment structures

The schedule on this page assumes a fully amortizing, fixed-payment loan, which is the most common consumer structure - but it helps to know what it is not. An interest-only loan charges only interest for an introductory period, so the balance does not fall at all until the principal phase begins, and payments jump sharply afterward. A balloon loan keeps payments low by amortizing on a long schedule but demands the entire remaining balance as a single large payment at a set date. A simple-interest or daily-accrual loan calculates interest on the exact number of days between payments, so paying a few days early or late nudges the split slightly compared with the clean monthly compounding modeled here. And a variable or adjustable-rate loan re-amortizes whenever the rate resets, changing the payment for the remaining term. This calculator is built for the standard fixed-rate case; if your loan uses one of these other structures, treat the output as a close approximation rather than an exact match.

Sources

• Consumer Financial Protection Bureau (CFPB) - Owning a Home: loan and amortization basics.
• Consumer Financial Protection Bureau (CFPB) - What is amortization?
• Federal Reserve - Consumer Credit (G.19): credit and interest rate data.