Loan Amortization & Mortgage Calculator
Compare level payments and equal principal, export monthly schedules, and compare lower payments with a shorter term after prepayment.
About this loan amortization & mortgage calculator
Compare level payments and equal principal, export monthly schedules, and compare lower payments with a shorter term after prepayment Computes exact algebraic and numerical metrics directly in your browser using IEEE 754 precision without round-trip latency.
Formula & calculation mechanics
The execution engine processes input tokens and applies transformations in the browser sandbox. Specifically, P is principal, i = annual rate / 1200, n = 12 × years. Level payment = P i / (1 − (1+i)^−n); when i = 0, P/n. Equal principal = P/n per month. Interest = opening balance × i. Amounts are rounded half up to cents using exact integer arithmetic. The last payment clears the remaining balance; rounding can cause an earlier payoff or a larger final adjustment, especially for tiny loans.
Worked numerical calculation
Scenario: Load example
Sample input:
Processing: P is principal, i = annual rate / 1200, n = 12 × years. Pay extra immediately after the selected month’s regular payment; month 0 is before interest accrues. Enter 0 to disable. The extra amount cannot exceed the selected plan’s remaining balance. Full payoff is allowed. Lower payments recalculates the installment over the remaining original term; shorter term keeps the original payment, or original principal installment for equal-principal loans.
Illustrative output:
Domain range & precision boundaries
Fixed rate, whole months and one currency with 2 decimal places. No daily accrual, irregular first/last periods, rate resets, fees, penalties or opportunity cost. Bank contracts and rounding policies can differ; this is a model, not a bank quote or certification. Lower interest alone does not determine the best personal choice. At most 1200 monthly rows per plan; no file upload. Use decimal points, no separators, signs or exponent notation. Principal and extra payment: 0–1000000000, up to 2 decimals. Rate: 0–100%, up to 6 decimals. Years: integer 1–100. Every field is required, at most 64 characters; surrounding spaces and leading zeros are allowed.
Calculations in Loan Amortization & Mortgage Calculator use standard IEEE 754 precision or exact rational models. Verify significant accounting or tax figures with authoritative references.
In-browser calculation boundary
Formula calculations and numeric evaluations in Loan Amortization & Mortgage Calculator run synchronously in the browser JavaScript engine with zero server telemetry.
Mathematical formulas & precision standards
Mathematical constants, IEEE 754 floating-point standards, and numerical analysis specifications:
- Fixed-rate monthly amortization: annuity and equal-principal methods; explicit cent rounding
Loan Amortization & Mortgage Calculator verification · Audit standards
How to use it
- Years: integer 1–100.
- Enter 0 to disable. Full payoff is allowed.
- Click the action button or observe immediate live calculations rendered by Loan Amortization & Mortgage Calculator.
Frequently asked questions
Model and assumptions+
Operational requirements for "Model and assumptions" are verified in local memory during execution of Loan Amortization & Mortgage Calculator.
Extra principal payment+
Enter 0 to disable. Full payoff is allowed.
Monthly schedule+
Choose a plan to view or export its entire schedule. CSV uses UTF-8 with BOM, localized headers, comma separators and fixed decimal points with 2 decimals. Month and monetary units match the table; total payment includes extra principal. Scroll the table horizontally on narrow screens.
Years (1–100)+
Years: integer 1–100.