Loan Amortization Calculator
Break any loan into its principal and interest components over time, and see exactly when your payment starts building equity faster than it pays the lender.
Loan Amortization Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: An amortisation schedule splits each payment between interest on the outstanding balance and principal reduction. Early payments are mostly interest: on a $336,000 loan at 6.5%, month one is $1,820.00 interest and only $303.75 principal, and the two do not cross over until month 233.
Formula
The payment is constant but its composition shifts every month as the balance falls, which is what produces the characteristic front-loaded curve.
Worked Example
- Fix the payment. $336,000 at 6.5% over 360 months = $2,123.75.
- Month 1 interest. $336,000 × 0.541667% = $1,820.00.
- Month 1 principal. $2,123.75 − $1,820.00 = $303.75, just 14.3%.
- Roll forward. After 12 months, $21,729.43 of interest and $3,755.57 of principal.
- Find the crossover. Principal first exceeds interest at month 233.
Analyst note. After a full year of payments totalling $25,485.00, the balance has fallen only $3,755.57. This is why selling within five years builds almost no equity, and why early overpayment is so disproportionately effective.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Understanding where your money actually goes
Seeing that 85.7% of the first payment is interest reframes the whole loan. It explains why balances barely move early on and why acceleration pays. Quantify that with the Extra Payment Mortgage Calculator.
Estimating equity at a planned sale date
Set the inspect month to your expected sale and read the balance. Combined with an appreciation estimate, that gives net proceeds — and the Rent Vs Buy Calculator puts it in context.
Evaluating a refinance mid-term
Refinancing resets you to the front of the curve. Compare the interest already paid against what a new schedule would cost using the Refinance Calculator.
Methodology & Editorial Standards
The schedule is computed iteratively rather than by closed-form approximation. Each period charges interest on the opening balance at the monthly rate, applies the remainder of the level payment to principal, and carries the reduced balance forward, with the final payment truncated to clear any residual. Cumulative figures are accumulated to the inspected month, and the crossover point is identified as the first period in which the principal component exceeds the interest component. The model assumes a fixed rate, level payments and no fees or escrow, so it reflects the note only. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Loan Amortization Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is an amortisation schedule?
A month-by-month breakdown of how each payment splits between interest and principal. The payment stays level but the composition shifts continuously, from 85.7% interest in month one to almost entirely principal at the end.
Why is so much of my early payment interest?
Because interest is charged on the outstanding balance, which is at its largest at the start. On $336,000 at 6.5%, month one accrues $1,820.00 of interest, leaving only $303.75 to reduce the debt.
When does principal exceed interest?
At month 233 on this loan — more than nineteen years into a thirty-year term. Higher rates push the crossover later; shorter terms pull it dramatically earlier.
How much equity do I have after five years?
Less than most people expect. After 60 payments totalling $127,425, the balance has fallen from $336,000 to $314,532.88 — about $21,467 of principal, against $105,957.80 of interest paid.
Does an extra payment change the schedule?
Yes, permanently. Every extra dollar of principal removes all future interest that dollar would have accrued, shortening the term. The payment amount stays the same; you simply make fewer of them.
Why does the last payment differ slightly?
Because rounding across hundreds of periods leaves a small residual. The final payment is truncated to clear exactly the remaining balance, which is how real servicers handle it too.
Is amortisation the same on a car loan?
The mathematics is identical, only the term and rate differ. A five-year auto loan crosses over almost immediately because the term is short relative to the rate, which is why car loans build equity far faster than mortgages.
What is negative amortisation?
When the payment does not cover the accrued interest, so the shortfall is added to the balance and the debt grows. It occurs on some adjustable and payment-option products and is a serious risk worth avoiding.
How does the term affect total interest?
Enormously. The same $336,000 at 6.5% costs $428,549.48 in interest over 30 years but far less over 15, because the balance falls much faster and there are half as many periods for interest to accrue.
Can I see the schedule for a refinanced loan?
Yes — enter the current balance and the new rate and term. That is the correct comparison, because refinancing amortises the remaining balance rather than the original loan amount.
Why does my servicer's schedule differ slightly?
Usually because of day-count conventions. Some servicers accrue interest daily on the actual number of days in each month rather than using a flat monthly rate, which shifts figures by a few dollars either way.
Does the schedule include taxes and insurance?
No. This models the note only — principal and interest. Escrowed taxes and insurance are collected alongside but are not part of the amortisation, since they do not reduce the loan balance.
Is this loan amortization calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.
Which currency does it use?
Amounts display in US$ accounting format, but the underlying mathematics is currency-agnostic. The result is identical in any currency, so simply read the figures in your own.
Why does a result show an em-dash?
An em-dash indicates the calculation is not defined for the inputs given — typically a division by zero or a value outside the valid domain. We show a dash rather than a misleading number.
How do I report an error?
Email apexconverter.praxiscalc@gmail.com with the tool URL, your exact inputs, the output received and the output you expected. Verified mathematical errors are patched within 72 hours.