Amortization Schedule Calculator
Calculate loan amortization schedule. See principal and interest breakdown for any payment, remaining balance, and total interest.
This calculator computes the full amortization breakdown for one specific payment out of a loan's schedule, selected via Payment Number, using the standard formula to first get Monthly Payment (lines 13-16) and then working out the Remaining Balance right before that payment (lines 19-20) via a closed-form balance formula rather than by simulating every prior month. At Payment Number 1 — the default — the Remaining Balance formula collapses so that Loan Term drops out of it entirely: Interest Payment ends up being Loan Amount times the monthly rate alone, an exact 20%-and-20% tie in sensitivity between Loan Amount and Annual Interest Rate, with Loan Term measurably inert. That is not a coincidence of the specific numbers; it is how the formula's exponent — Payment Number minus one, which is zero at Payment Number 1 — behaves algebraically. Principal Payment inherits none of that inertness, though: it is a small residual, Monthly Payment minus the much larger fixed Interest Payment, so the same modest 7% swing that Loan Term produces in Monthly Payment translates into roughly a 46% swing in the smaller Principal Payment figure, because subtracting two close numbers amplifies the relative sensitivity of what is left over. Total Interest is nearly evenly split between Annual Interest Rate and Loan Term — run each one 10% below its default and then 10% above it, and Total Interest swings by about 24% across that range, both ahead of Loan Amount's 20% swing. Payment Number itself never moves Monthly Payment or Total Interest — it only changes which single payment's principal and interest split gets reported. This calculator does not track extra payments, rate changes mid-loan, or any payment actually made; Payment Number just selects a row from the theoretical fixed-rate schedule.
Financial Disclaimer
This calculator is for educational purposes only and does not constitute financial advice. Results are estimates based on the inputs provided. Consult a qualified financial advisor before making investment or financial planning decisions.
Inputs
Summary
Monthly Payment
$1,264.14
≈ 10 pairs of sneakers
Remaining Balance
$199,819.20
≈ 13 used cars
Total Interest
$255,088.98
≈ 6 Teslas
Remaining Balance Over Time
Principal vs Interest
How to Use This Calculator
- Enter the loan amount (principal).
- Set the annual interest rate on the loan.
- Enter the loan term in years.
- Choose a specific payment number to see exactly how much goes to principal versus interest at that point.
- Review the monthly payment, total interest paid over the life of the loan, and total cost.
How the result changes with Loan Amount
| Loan Amount | Monthly Payment | Remaining Balance | Total Interest |
|---|---|---|---|
| $80,000.00 | $505.65 | $79,927.68 | $102,035.59 |
| $280,000.00 | $1,769.79 | $279,746.88 | $357,124.57 |
| $520,000.00 | $3,286.75 | $519,529.91 | $663,231.34 |
| $720,000.00 | $4,550.89 | $719,349.11 | $918,320.32 |
What each input means
- Loan Amount
- Principal loan amount
- Annual Interest Rate
- Annual interest rate
- Loan Term
- Loan term in years
- Payment Number
- Which payment to analyze (default: 1)
How this is calculated
Formula
Monthly Payment = P × [r(1+r)^n] / [(1+r)^n - 1]Worked example, using the default values
- Identify Input Parameters4 parametersLoan Amount = 200000, Annual Interest Rate = 6.5, Loan Term = 30, Payment Number = 1 = 4 input(s) provided
- Calculate Monthly PaymentMonthly Payment1264.1360469859305 = $1,264.136
- Calculate Remaining BalanceRemaining Balance199819.1972863474 = $199,819.197
- Calculate Total InterestTotal Interest255088.976914935 = $255,088.977
- Calculate Interest PaymentInterest Payment1083.3333333333333 = $1,083.333
- Calculate Principal PaymentPrincipal Payment180.80271365259728 = $180.803
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.
Frequently Asked Questions
What determines Interest Payment for the first payment of the loan?
Loan Amount and Annual Interest Rate are in an exact tie at these defaults — take either one 10% below its default and 10% above it, and the total swing in Interest Payment across that range comes out to exactly 20%. That is because at Payment Number 1, Interest Payment reduces algebraically to Loan Amount times the monthly rate alone, a plain product of the two, with no dependence on Loan Term at all.
Does a longer loan term change how much interest is in the first payment?
No — Loan Term has zero measured effect on Interest Payment at Payment Number 1, because the Remaining Balance formula's exponent is Payment Number minus one, which equals zero at the first payment. That makes the term-dependent part of the formula vanish algebraically, leaving Interest Payment set purely by Loan Amount and Annual Interest Rate.
Why does Loan Term have such an outsized effect on Principal Payment?
Surprisingly large — a swing of about 46% across a ±10% probe, versus only about 7% for Monthly Payment itself. Principal Payment is the small difference between Monthly Payment and the much larger, fixed Interest Payment, so a modest dollar change in Monthly Payment is a much bigger percentage change in what is left over after interest is subtracted.
Does the interest rate or the loan term drive Total Interest more?
Neither one clearly leads — Annual Interest Rate and Loan Term move Total Interest by almost the same margin, each spanning about 24% of Total Interest across a ±10% probe, ahead of Loan Amount's 20% span. Unlike Interest Payment at Payment Number 1, Total Interest is the sum over the whole schedule, so both rate and term compound through it about equally.
What does Remaining Balance show at the very last payment of the loan?
At Payment Number 360 — the final payment of the default 30-year, 360-payment schedule — Remaining Balance comes out to essentially $0, confirming the loan fully amortizes by its last payment rather than leaving a residual balance. At Payment Number 1, by contrast, Remaining Balance comes out to about $199,819.19 at these defaults — not the full $200,000 Loan Amount. The reported Remaining Balance is always the balance immediately AFTER the selected payment is applied (Loan Amount minus that payment's roughly $180.81 Principal Payment), not the balance before it.
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