An amortization calculator estimates a payment-by-payment schedule for a fixed-rate loan, showing how each modeled payment is divided between interest and principal and how the balance changes over time. This tool supports monthly or annual payments, recurring extra payments, and a one-time extra amount with the first payment.
Whether you are financing a home mortgage, purchasing a vehicle, or managing a fixed-rate personal loan, knowing how your loan amortizes reveals the true cost of debt over time.
How to Use the Amortization Calculator
- Enter the loan basics: Type the Loan Amount, choose the Currency, and enter the Annual Interest Rate (% p.a.), using 0 for an interest-free loan.
- Choose the frequency: Pick Monthly or Annual under Payment Frequency. Monthly is standard for mortgages, auto loans, and personal loans, while Annual suits some business and private loans.
- Set the term: Fill in the Loan Term in Years and/or Months, between 1 and 600 months, with one schedule row generated per month.
- Time it and add extras: Optionally set a Start Date, enter an amount under Extra Each Period that is paid on top of every scheduled payment, and add a One-Time Extra that is applied with the first payment.
- Calculate: Click Calculate to see the Monthly Payment, Total Paid, Total Interest, Payments, and Paid Off date, plus the "Saved vs Scheduled" figure when you use extras.
Open View Amortization Schedule for every payment's principal, interest, and balance, and check the Balance Over Time chart for the crossover month where principal starts to outweigh interest.
Choosing Monthly or Annual Payments
The calculator supports two payment frequencies. The selected frequency determines the number of modeled periods and the rate applied to each period:
- Monthly: The entered annual rate is divided by 12 and the schedule has one payment period per month.
- Annual: The entered annual rate is applied once per year and the schedule has one payment period per year. This is a model option and may not match the terms of a typical consumer loan.
Modeling Extra Principal Curtailments (Recurring vs One-Time)
- Extra each period: Adds the amount you enter to each scheduled monthly or annual payment.
- One-time extra: Adds the amount to the first scheduled payment only; the tool does not let you choose a later period.
Anatomy of an Amortization Schedule
Amortization is the process of repaying a loan through scheduled payments that cover interest and reduce principal over time. This calculator estimates the payment, interest, principal, remaining balance, and payment date for each modeled period.
Why early payments include more interest
On a level-payment fixed loan, the total dollar amount paid each period remains similar while its allocation changes over time. In this tool's monthly model, each period's interest is the outstanding balance multiplied by the entered annual rate divided by 12.
Because the initial principal balance is at its maximum at the start of the loan, the resulting interest charge is also at its peak.
The Principal-Interest Crossover Milestone
The principal-interest crossover point is the specific payment period in which the dollar portion applied toward principal reduction exceeds the dollar portion consumed by interest charges.
With no extra payment, the model reaches this point at payment 223 on a 30-year, $200,000 loan at 6.00%, and at payment 43 on a 15-year loan with the same principal and rate. Your result changes with the loan amount, rate, term, and extra payments.
The Standard Amortization Formula Explained
For a fixed rate, the calculator uses a level-payment formula based on the number of payment periods and the rate per period. The last modeled payment is adjusted to clear the remaining balance.
Solving for the Fixed Periodic Payment
The periodic payment M is calculated using the following equation:
M = P * [ r(1 + r)^n ] / [ (1 + r)^n - 1 ]
Where:
- M: Total periodic payment per installment.
- P: Initial loan principal borrowed.
- r: Rate per period: annual rate divided by 12 for monthly payments, or the annual rate for annual payments.
- n: Number of payment periods in the entered term.
Plugging in the tool's test case: a $200,000 loan at 6.00% over 360 monthly payments has r = 0.06 ÷ 12 = 0.005 and n = 360, so (1.005)360 = 6.022575. That gives M = 200,000 × [0.005 × 6.022575] ÷ [6.022575 − 1] = 200,000 × 0.0301129 ÷ 5.022575 = $1,199.10 exactly. The calculator carries the walk in whole cents and rounds the payment up to $1,199.11, absorbing the residue in the final payment — which is how the schedule arrives at its stated $1,199.11 payment and $231,670.80 total interest.
Calculating Interest for Each Payment Period
For each individual billing period t, the interest component and principal reduction are determined through sequential accounting:
I = B * r
Prin = Payment - I
New balance = B - Prin
Here B is the balance at the start of the period and Payment includes the scheduled payment plus any extra for that period. Interest is rounded to cents; a final payment is adjusted to clear the modeled balance.
Worked example: $200,000 loan at 6.00%.
The table below demonstrates the baseline 30-year repayment schedule compared to an accelerated schedule with a $100 recurring monthly principal curtailment, calculated by the calculator:
| Repayment Metric | Baseline Schedule | With $100/mo Extra Principal | Variance / Benefit |
|---|---|---|---|
| Principal Borrowed | $200,000.00 | $200,000.00 | Identical initial debt |
| Nominal Interest Rate | 6.00% | 6.00% | Identical contract rate |
| Scheduled Monthly Payment | $1,199.11 | $1,299.11 ($1,199.11 + $100) | +$100.00 / month |
| Total Payments Made | 360 payments (30.0 yrs) | 295 payments (24.6 yrs) | Saved 65 payments (5 yrs 5 mos) |
| Total Interest Accrued | $231,670.80 | $182,534.40 | Saved $49,136.40 in interest |
| Total Amount Repaid | $431,670.80 | $382,534.40 | Net savings of $49,136.40 |
| Principal-Interest Crossover | Month 223 | Payment 157 | 66 payments earlier |
Ways to use an amortization schedule
An amortization schedule is an essential decision-making tool for managing household liabilities, forecasting net worth, and evaluating debt restructuring.
Accelerating Equity Accumulation in Real Estate & Auto Loans
In real estate financing, slow initial principal reduction means the loan balance stays high relative to the property value for several years. Reviewing your amortization table reveals how minimal surplus payments rapidly compress the interest-heavy front half of the loan.
Predicting Remaining Balance for Refinance or Resale Timing
If you plan to sell a property or trade in a vehicle after five years (60 months), the schedule can estimate the remaining balance. On a 30-year, $200,000 loan at 6%, the model shows $71,946.60 paid over 60 monthly periods and a remaining balance of $186,108.10.
Comparing 15-year vs 30-year loan terms
Evaluating the trade-off between monthly cash flow and long-term borrowing costs is central to debt planning:
| Loan Term | Monthly Payment | Total Interest Paid | Total Cost ($200,000 at 6%) |
|---|---|---|---|
| 15 Years (180 months) | $1,687.72 | $103,787.75 | $303,787.75 |
| 30 Years (360 months) | $1,199.11 | $231,670.80 | $431,670.80 |
| Difference | +$488.61 / month | -$127,883.05 in interest | Save $127,883.05 overall |
Limits of this amortization model
Understanding loan contract mechanics ensures your debt payoff strategy performs as intended without bank-side friction.
Why Extra Payments Must Be Marked "Principal Curtailment"
The tool assumes extra payments reduce the modeled balance in the period they are made. A lender or servicer may apply extra funds according to the contract and its payment instructions, so confirm whether an extra amount will reduce principal, advance a due date, or be handled another way.
If your goal is to reduce principal, follow the servicer's instructions for making a principal-only payment and check your next statement to confirm how it was applied. The calculator's estimate cannot guarantee a servicer will handle an extra payment in the same way. The CFPB's guidance on prepaying a loan notes that many loans can be repaid early without a penalty while some carry one, usually limited to the early years, so read the prepayment clause before treating an extra payment as free. A penalty does not change whether extra principal saves interest; it changes how much of the saving survives.
Differences Between Simple Interest and Rule of 78 Amortization
This model uses a fixed rate applied once per selected period. It does not model daily interest accrual, changing rates, balloon payments, or precomputed-interest methods such as the Rule of 78.
If your loan uses a different interest or early-payoff method, the calculator's schedule may not match the lender's payoff amount. Check your contract or ask the lender how it calculates interest and handles early repayment.
To evaluate broader borrowing options or assess standalone financing structures, compare schedules with our Loan Payment Calculator, examine property-specific amortization with our Mortgage Calculator, or map early debt settlement milestones using our Loan Payoff Calculator. To isolate the interest portion of those payments, use the Loan Interest Calculator; for a land note with a balloon or shorter term, model it with the Land Loan Calculator.
An amortization calculator is a loan tool: a HELOC repayment phase amortizes on a schedule once the draw period ends, and a personal loan amortizes the same way. Investments and savings do not amortize at all; growth accounting for those belongs to the Compound Interest Calculator.
Last verified: October 2026. Calculator figures are outputs for the inputs entered; they are not live quotes, current rates, or an offer.