| Metric | Value | Copy |
|---|---|---|
| Monthly payment ($) | {{ format(monthlyPayment) }} | |
| Total principal ($) | {{ format(totalPrincipal) }} | |
| Total interest ($) | {{ format(totalInterest) }} | |
| Total paid ($) | {{ format(totalPaid) }} | |
| Months to payoff | {{ payoffMonths }} |
| Month | Payment ($) | Principal ($) | Interest ($) | Balance ($) | Copy |
|---|---|---|---|---|---|
| {{ r.period }} | {{ format(r.payment) }} | {{ format(r.principal) }} | {{ format(r.interest) }} | {{ format(r.balance) }} |
Personal loans are fixed term borrowing repaid in equal monthly installments that combine interest with principal as the balance declines. A personal loan amortization calculator shows how the payment is determined and how long it takes to finish.
Provide a loan amount, a yearly percentage rate, and a term in years and months, then read the monthly payment and months to payoff. Add optional prepayments to see how extra amounts reduce total interest and shorten the schedule.
For example, a borrower might compare plans for a renovation and check how a small extra payment each month trims interest and knocks several months off the end date. Use consistent inputs so results are comparable across scenarios.
Rounding to cents makes the final installment adjust slightly so the balance reaches zero. Enter realistic numbers and avoid mixing different unit conventions to keep results sensible.
The quantities measured are principal, rate, time, and cash flows for a level‑payment installment loan. The yearly percentage rate is transformed into a monthly rate so a constant base payment is computed, then each period’s payment is split into interest and principal as the balance declines.
The computation first finds a base payment that would amortize the principal over the chosen number of months. Optional prepayments are applied on top of that base as a fixed extra each month, a once‑per‑year addition at months 12, 24, and so on, and a one‑time lump sum at a chosen month. The last payment is reduced if needed so the remaining balance reaches zero.
Results are interpreted as follows: the “Monthly payment” value reflects the constant base payment plus any recurring monthly extra; annual and lump‑sum prepayments do not change that headline figure but do shorten the payoff time and reduce total interest. “Months to payoff” equals the number of scheduled periods generated.
Comparability assumes a fixed rate with monthly compounding and constant timing of payments. Because cents rounding is applied, small differences can appear when comparing scenarios with many prepayments or long durations.
| Symbol | Meaning | Unit/Datatype | Source |
|---|---|---|---|
| P | Principal (loan amount) | $ | Input |
| APR | Annual percentage rate | % per year | Input |
| r | Monthly rate | fraction per month | Derived |
| n | Number of months | months | Derived |
| Mbase | Base level payment without prepayments | $ | Computed |
| xM | Extra monthly prepayment | $ | Input |
| xA | Extra annual prepayment (months 12, 24, …) | $ | Input |
| L | One‑time lump sum | $ | Input |
| mL | Month index of lump sum | month ≥ 1 | Input |
| Bt | Balance after month t | $ | Computed |
| It | Interest in month t | $ | Computed |
| Parameter | Meaning | Unit/Datatype | Typical Range | Sensitivity | Notes |
|---|---|---|---|---|---|
| Loan amount | Borrowed principal | $ | 1,000–100,000 | High | Must be > 0 to compute. |
| Interest rate | APR as a percent (not decimal) | % per year | 0–40 | High | 7 means 7% yearly. |
| Term | Years plus extra months | years, months | 1–10 years | High | Months use 0 to 11. |
| Prepayments | Monthly, annual, lump sum | $ | 0–10% of P | Medium | Shorten payoff and cut interest. |
Displayed amounts use two decimals with the locale’s decimal separator. Per‑row payment, interest, and principal are rounded to cents; the final balance is shown as $0 when the residual is below one cent. The headline monthly payment rounds to two decimals and includes only the recurring monthly extra.
| Field | Type | Min | Max | Step/Pattern | Error Text | Placeholder |
|---|---|---|---|---|---|---|
| Loan amount | number | 0 | — | — | — | — |
| Interest rate (%/yr) | number | 0 | — | 0.01 | — | — |
| Term years | number | 0 | — | — | — | — |
| Term months | number | 0 | 11 | — | — | — |
| Extra monthly | number | 0 | — | — | — | — |
| Extra annual | number | 0 | — | — | — | — |
| Lump sum | number | 0 | — | — | — | — |
| Lump sum month | number | 1 | — | — | — | — |
| Input | Accepted Families | Output | Encoding/Precision | Rounding |
|---|---|---|---|---|
| Numbers | principal, APR, years, months, prepayments | Metrics and schedule | Two decimals for money | Per row to cents; final adjust |
| Copy/Download | CSV, JSON | Loan metrics, amortization rows | UTF‑8 text | Values as shown |
All calculations run in the UI layer. Copy actions use the clipboard, and CSV/JSON files are generated locally; no network requests are required.
Schedule generation runs once per period (O(n)) and stops early when the balance falls below one cent or after 6,000 months, whichever comes first. Charting reuses precomputed arrays.
Identical inputs yield identical outputs. Minor differences can appear when large prepayments trigger an earlier final period due to cents rounding.
No secrets or credentials are involved. Inputs are numeric and constrained; downloads contain only the values you entered and the computed results.
Processing is client‑only and data is not sent to a server. Outputs are educational and not financial advice.
Personal loan payments and payoff time are estimated from your principal, rate, and term, with optional prepayments applied.
Example: $15,000 at 7 for 3 years produces about $463.16 per month and 36 months to payoff without prepayments.
You now have a clear payment and a plan to finish on time or sooner.
No. Calculations happen in the UI and downloads are created locally. Nothing is sent to a server.
Clipboard and file permissions are handled by your device.Payments and per‑row amounts round to cents. The last installment adjusts so the remaining balance reaches zero to within one cent.
Rounding can cause tiny differences between scenarios with many prepayments.Enter dollars for amounts, a yearly percentage for the rate, and years plus 0 to 11 extra months for the term.
Yes. No network requests are required for calculation, copying, or saving files.
If the last row shows a very small payment, rounding has pulled the payoff forward by one period. That is normal and expected.
Use the amortization formula with a monthly rate from APR and the number of months, then add any recurring monthly extra you plan to pay.
No licensing terms are provided in the package. Treat outputs as informational for planning purposes.
Tip Test the effect of a small monthly extra versus a single lump sum to see which suits your cash flow.
Tip Keep term months within 0 to 11 so years and months are unambiguous.
Tip Round your planned payments to whole dollars to make budgeting simpler.
Tip Use the schedule to spot when interest falls below principal each month.
Tip Try an annual prepayment timed near month 12 to see its impact.
Tip Save a JSON snapshot to compare scenarios over time.