Introduction:
A mortgage amortization schedule breaks each payment into principal and interest, illustrating how the outstanding balance falls over time. Understanding this split lets you compare loan options, adjust repayment frequency, include taxes or insurance, and forecast long-term costs across the full loan term, helping you decide when refinancing or extra payments make sense.
The mortgage calculator accepts the property price, down payment, interest rate, loan term, and optional extras such as property tax, insurance, homeowners association fees, private mortgage insurance, and lump-sum repayments. It instantly computes periodic payments for monthly or bi-weekly schedules, generates a detailed amortization table, and renders interactive charts that show payment composition, cumulative totals, and balance trends.
Use it to see how rate, term, or additional payments influence total cost before committing to a loan; figures are estimates—confirm exact terms with your lender.
Technical Details:
Periodic mortgage payments follow an annuity formula that converts the annual percentage rate into a per-period rate and evenly amortizes the initial principal over a fixed number of periods.
The calculator extends this formula with linear additions for taxes, insurance, association fees, and optional mortgage insurance, producing one consolidated payment for each selected frequency.
The periodic rate equals the annual rate divided by the number of payments per year. Principal reduction grows over time because the interest portion shrinks as the remaining balance declines, forming the classic amortization curve.
- Principal (P): borrowed amount after down payment
- Rate (r): periodic interest rate in decimal form
- Periods (n): total payments across loan term
- Payment (M): base periodic principal-interest sum
| Extra cost input | Inclusion method |
|---|---|
| Property tax | Annual rate or amount prorated per period |
| Insurance | Annual amount prorated per period |
| HOA fee | Flat monthly amount or bi-weekly equivalent |
All calculations execute entirely in your browser, keeping financial data private and providing instant feedback.
Calculations & Scoring:
The base periodic payment uses the standard amortization formula shown below.
| Symbol | Meaning |
|---|---|
P | Principal (loan amount) |
r | Periodic interest rate (decimal) |
n | Total number of periods |
M | Base periodic payment |
Divides the annual rate by the number of payments per year.
Finds the factor that normalises the payment across all periods.
Multiplies principal factor by the corrected ratio to yield the periodic amount.
Final Result
The example yields a periodic payment of $1 432.25.
Higher extra payments reduce amortization time and total interest quickly.
Step-by-Step Guide:
Follow these steps to model your mortgage scenario.
- Select Loan amount and enter the property price.
- Enter Down payment, then choose % or $.
- Set Interest rate and Loan tenure in years.
- Open Advanced and pick Payment frequency.
- Add Extra payment or Lump sum if planning early repayment.
- Optionally fill taxes, insurance, HOA fees, and PMI details.
- Review the schedule, charts, and use Download CSV to export results.
FAQ:
Common questions about calculations, inputs, and privacy.
What does the periodic payment include?
It combines principal, interest, optional extra payment, prorated tax, insurance, PMI, and HOA amounts based on your inputs.
How are bi-weekly payments calculated?
The annual interest rate is divided by 26 and the loan term is converted into total bi-weekly periods, then the same amortization formula is applied.
Can I model early repayment?
Yes. Enter a regular extra payment, a one-time lump sum at a specific period, or both to see the updated schedule and interest savings.
Is my data stored?
No. All calculations run locally in your browser; nothing is transmitted or stored on any server.
What if interest rates change later?
This calculator assumes a fixed rate. To explore new rates, adjust the interest field and compare schedules side by side.
Troubleshooting:
Resolve common issues quickly.
Payment shows “NaN” — Ensure all numeric inputs are filled and use a dot for decimals.
Unexpected currency symbol — Choose the desired currency code in the settings panel.
Charts appear blank — Switch tabs to refresh or resize your window; the charting layer resizes responsively.
CSV fails to download — Disable pop-up blockers or try a different browser.
PMI input hidden — Set down payment below 20 % and enter a positive PMI rate to reveal the field.
Advanced Tips:
Fine-tune your scenarios with these expert hints.
- Test multiple currencies to compare international property options.
- Use URL parameters to bookmark specific input sets and share results.
- Compare monthly versus bi-weekly schedules to measure interest savings.
- Apply a realistic property tax percentage based on local rates.
- Model staggered lump sums by exporting CSV and editing in a spreadsheet.
Glossary:
Key terms used throughout the calculator.
- Amortization
- Gradual repayment of debt over scheduled periods.
- Principal
- Outstanding loan balance excluding interest.
- Interest
- Cost charged by the lender for borrowing money.
- PMI
- Insurance protecting lenders when down payment is under 20 %.
- Lump sum
- One-time extra payment applied to the balance.