FAQs
How accurate is this mortgage amortization calculator?
It is mathematically precise for standard fixed-rate loans. Accuracy depends on your inputs. The amortization schedule matches standard banking formulas used for conventional mortgages.
Can I calculate amortization manually instead?
Yes, but it requires solving complex exponential equations and repeating calculations for each month (up to 360 times). This calculator automates that tedious, error-prone process.
What causes PMI to appear or disappear from the schedule?
PMI appears when your down payment is less than 20% (LTV ≥ 20%). It disappears from the schedule when your remaining loan balance reaches 78% of the original home value, as required by federal law for automatic PMI termination.
Is this tool safe for sensitive financial planning?
Yes. The tool runs entirely client-side using JavaScript. No data you enter is transmitted to or stored on any server. It is completely safe for private use.
What is the difference between an amortization schedule and a payment schedule?
A payment schedule only shows the total amount due each month. An amortization schedule (provided in this tool’s second tab) breaks down exactly how much of that payment goes to principal, interest, and PMI, plus the remaining balance after each payment.
How does choosing Bi-Weekly payments change my amortization?
Bi-weekly payments result in 26 half-payments per year, which equals 13 full monthly payments annually. This extra payment reduces your principal faster, shortens your loan term, and decreases total interest compared to monthly payments.
Why does the PMI end date show “Never reaches 78% LTV”?
This appears when your starting down payment is so low (e.g., 3-5%) that, at your current interest rate, your principal balance never drops to 78% of the home value within the loan term. This can happen with very long terms or very low interest rates.
What does the “Grand Total” cost include?
The Grand Total includes: all Principal payments (the original loan amount), all Interest paid over the full term, all PMI paid until termination, and all Other Monthly Costs multiplied by the number of months.
Can I use this calculator for an existing mortgage?
Yes. Enter your current remaining loan balance as the “Home Value” (or leave it as the original value), your current balance as the “Loan Amount,” and your current interest rate and remaining term. The schedule will show your remaining amortization.
Does this tool account for extra monthly payments?
The current version calculates standard scheduled payments only. To see the effect of extra payments, you would need to manually deduct extra principal from the “Remaining Balance” column in the schedule and observe the shortened term.
What is the 78% LTV rule for PMI termination?
The federal Homeowners Protection Act requires lenders to automatically terminate PMI when your mortgage balance reaches 78% of the original property value, assuming you are current on payments. This calculator models that exact threshold.
Why does my amortization schedule show a different total interest than my lender quote?
Lender quotes may include additional fees, different compounding methods, or assumptions about escrow. This calculator uses standard amortization math on your exact inputs. Small discrepancies can also arise from rounding in the displayed table versus underlying calculations.
