| Month | Payment ($) | Principal ($) | Interest ($) | Balance ($) |
|---|---|---|---|---|
| {{ r.period }} | {{ format(r.payment) }} | {{ format(r.principal) }} | {{ format(r.interest) }} | {{ format(r.balance) }} |
Amortised personal loans spread repayment of principal and accrued interest across equal instalments, typically on a monthly cycle. Each payment progressively shifts composition from mostly interest toward mostly principal, governed by the loan’s stated annual percentage rate and repayment term. Understanding this glide-path helps borrowers compare offers, budget accurately, and evaluate how extra contributions shorten debt duration.
The calculator processes your loan amount, annual interest rate, and term length, then models optional extra monthly, yearly, or lump-sum payments. It outputs the fixed minimum instalment, totals for principal versus interest, and a month-by-month amortisation table. Interactive charts illustrate balance decay, cumulative interest, payment composition, and an overall cost breakdown.
Experiment with refinancing offers, test accelerated repayment strategies, or download the full amortisation schedule for spreadsheet modelling and record-keeping. Adjust extra payments until the interest portion falls within your budget comfort zone, then share the schedule with stakeholders for informed decision-making. Results are estimates and do not replace personalised financial or tax advice.
The model treats the loan as a fully amortising, fixed-rate obligation with monthly compounding. Each period’s interest equals the outstanding balance multiplied by the nominal periodic rate, while principal equals the scheduled payment minus that interest. Extra contributions directly reduce the balance, shortening the schedule and trimming total interest. A lightweight reactive engine recalculates results whenever you adjust parameters, and a client-side charting layer renders four complementary visualisations.
Because all calculations run in the browser, there is no latency from network calls and no server-side persistence of personal data. Iterative simulation continues until the remaining balance falls below one cent or a 5 000-year guardrail, protecting against runaway loops.
1 – (1 + r)–n.
| Symbol | Meaning | Unit | Typical Range | Sensitivity |
|---|---|---|---|---|
| P | Loan principal | $ | 1 000 – 100 000 | High |
| r | Monthly interest rate | % | 0.1 – 2.5 | High |
| n | Total number of months | months | 6 – 360 | High |
| xM | Extra payment each month | $ | 0 – 500 | Medium |
| xA | Extra payment each year | $ | 0 – 2 000 | Medium |
| L | One-time lump sum | $ | 0 – P | High |
| mL | Month of lump sum | month | 1 – n | Medium |
P / n.The iterative schedule runs in O(n) time and uses linear memory proportional to the number of periods, typically under 10 KB. JavaScript’s double-precision floats maintain sub-cent accuracy for balances below one quadrillion dollars. All graphics rely on a vector-based charting layer that reflows on window resize without re-computation.
Follow these steps to model a loan and explore payoff scenarios.
The tool applies the standard amortisation formula using your inputs, then subtracts any extra contributions before carrying the balance to the next period.
Convert the bi-weekly amount to an equivalent monthly value or use the extra monthly field to approximate the effect; the schedule assumes monthly compounding.
No. All numbers remain in your browser’s memory and disappear when you close the page.
Rounding to two decimals may leave a tiny remainder; the algorithm adjusts the last period to clear the balance exactly.
No. The results provide general estimates and should not be the sole basis for lending or investment decisions.