Amortization Calculator — Schedule, Split & Payoff Date
See every payment of your loan: the interest and principal split, escrow and PMI, total cost and payoff date. Model extra payments under US or UK conventions.
A clear path from inputs to results.
Build a complete loan amortization schedule: the level payment, how each month splits between interest and principal, and the date the balance reaches zero. It covers mortgages, vehicle and student loans under US, UK or universal conventions, with escrow, PMI, UK SVR reversion and extra principal payments. Every number recalculates as you move the sliders.
How to use
- Enter the loan principal, APR and term. Term presets (5, 10, 15, 30 years) are one click away and a slider covers 1 to 40 years.
- Pick the jurisdiction (US, UK or Universal) and the asset class (mortgage, vehicle or student) — this switches on the region- and loan-specific logic described below.
- In US mortgage mode, add annual property tax and hazard insurance to see the escrowed monthly total, plus a monthly PMI amount and the month it stops.
- In UK mode, set the fixed-rate period and the reversionary SVR; the schedule reprices the payment when the fixed deal ends, with optional daily interest accrual.
- Open Acceleration and enter a monthly extra (yearly and one-time extras with their own date are also accepted by the engine) to see the shortened payoff and interest saved.
- Read the results: the headline payment, total interest and total cost, payoff date, the balance-versus-cumulative-interest chart, and the month-by-month ledger.
The formula
Reference: Standard annuity-immediate amortization formula (Broverman, Mathematics of Investment and Credit), evaluated with expm1/log1p for numerical stability. The APR is treated as a nominal annual rate compounded monthly — the usual US consumer-loan payment convention. Reg Z Appendix J defines the actuarial APR itself, which includes finance charges and is not simply the note rate divided by twelve.
Worked example
US mortgage, $200,000, 30-year fixed at 6.5%
- Principal $200,000; APR 6.5%; term 30 years; start January 2026; US region, mortgage asset class; property tax $2,400/yr; insurance $1,200/yr; PMI $0; no extra payments.
- 1
The monthly rate is 6.5% ÷ 12 = 0.541667%, and the annuity factor applied to $200,000 gives a principal-and-interest payment of $1,264.14. Escrow adds $2,400 ÷ 12 = $200.00 of tax and $1,200 ÷ 12 = $100.00 of insurance, so the first ledger row shows $1,564.14. Month one accrues $200,000 × 0.541667% = $1,083.33 of interest, leaving $1,264.14 − $1,083.33 = $180.81 of principal. The interest share shrinks every month as the balance falls, and summing the interest column across all 360 rows gives $255,085.82, for a total cost of $455,085.82 and a payoff in January 2056.
Payment $1,564.14 per month ($1,264.14 principal and interest plus $300.00 escrow); total interest $255,085.82; total cost $455,085.82; payoff January 2056.
Interpreting the result
The schedule is the decision tool: the payment tells you what the loan costs each month, while the total-interest column shows the true price of the rate and term you chose. Because month one is about 86% interest ($1,083.33 of a $1,264.14 payment), extra principal paid in the early years has a much larger effect on total cost than the same amount paid late. Use the ledger to see exactly when the principal share overtakes interest on your loan.
Assumptions & limitations
- The rate is fixed for the whole term; the payment is level and interest accrues monthly on the outstanding balance (US Reg Z style).
- US vehicle and student loans, and UK loans with daily accrual enabled, approximate daily interest as balance × APR ÷ 365.25 × 30.4375 average days per month.
- Property tax and insurance are flat amounts added to the displayed payment; the amortization ledger itself covers principal, interest, extra principal and PMI only.
- In US mortgage mode, PMI is a constant monthly amount charged while the balance exceeds 78% of the original principal and the month is at or before the drop-off month you enter.
- The ledger displays up to 360 rows; longer schedules still compute totals, charts and the payoff date correctly.
Frequently asked questions
How much does an extra $100 a month save?
Adding $100 of principal every month retires the worked-example loan in 293 months instead of 360 — about 5.6 years early — and cuts total interest from $255,090.40 to $199,141.44, a saving of $55,948.96. Every extra dollar goes straight to principal, so the saving compounds for the whole remaining term.
Why are the early payments almost all interest?
Interest is charged on the outstanding balance, which is largest at the start: month one of the worked example accrues $1,083.33 against a $1,264.14 payment, so only $180.81 reduces principal. As the balance falls, the interest slice shrinks and the principal slice grows — on a 30-year loan the crossover happens in the second half of the term.
Is loan interest tax-deductible here?
US mortgage mode estimates it: interest on a principal up to $750,000 is shown as deductible under current TCJA limits, with the deductible share scaled down above that. Student-loan mode caps estimated deductible interest at $2,500, and personal vehicle interest is flagged as not deductible. This is an estimate, not tax advice.
When does PMI appear and disappear?
In US mortgage mode the tool adds your entered monthly PMI whenever the balance is above 78% of the original principal, through the drop-off month you enter (78 by default). PMI does not change the principal-and-interest payment; it appears as its own column and stops once the balance or date condition is met.
What changes in UK mode?
The currency switches to pounds and the payment is repriced when your fixed-rate period ends: after the fixed months, the remaining balance is re-amortized at the reversionary SVR you enter, so a payment steps up if the SVR is above the fixed rate. With daily interest enabled, interest accrues on the average-day approximation instead of the monthly convention.
Can I model a one-time lump sum?
Yes — the engine accepts a one-time extra with its own date, a yearly extra (applied each January) and a monthly extra. All of them go to principal on top of the regular payment, and the schedule, payoff date and interest saved update immediately.
Methodology last reviewed 2026-10-06. Results are informational and not financial or engineering advice — see our disclaimer.