See the full amortisation schedule for a loan and what extra monthly payments really do: move the payoff date forward and cut the total interest, in hard numbers. Runs entirely in your browser — your numbers never leave this device.
| Year | Paid | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 | $8,394.60 | $2,461.55 | $5,933.05 | $97,538.45 |
| 2 | $8,394.60 | $2,613.38 | $5,781.22 | $94,925.07 |
| 3 | $8,394.60 | $2,774.58 | $5,620.02 | $92,150.49 |
| 4 | $8,394.60 | $2,945.70 | $5,448.90 | $89,204.79 |
| 5 | $8,394.60 | $3,127.39 | $5,267.21 | $86,077.40 |
| 6 | $8,394.60 | $3,320.28 | $5,074.32 | $82,757.12 |
| 7 | $8,394.60 | $3,525.06 | $4,869.54 | $79,232.06 |
| 8 | $8,394.60 | $3,742.49 | $4,652.11 | $75,489.57 |
| 9 | $8,394.60 | $3,973.31 | $4,421.29 | $71,516.26 |
| 10 | $8,394.60 | $4,218.38 | $4,176.22 | $67,297.88 |
| 11 | $8,394.60 | $4,478.57 | $3,916.03 | $62,819.31 |
| 12 | $8,394.60 | $4,754.78 | $3,639.82 | $58,064.53 |
| 13 | $8,394.60 | $5,048.07 | $3,346.53 | $53,016.46 |
| 14 | $8,394.60 | $5,359.40 | $3,035.20 | $47,657.06 |
| 15 | $8,394.60 | $5,689.95 | $2,704.65 | $41,967.11 |
| 16 | $8,394.60 | $6,040.89 | $2,353.71 | $35,926.22 |
| 17 | $8,394.60 | $6,413.50 | $1,981.10 | $29,512.72 |
| 18 | $8,394.60 | $6,809.08 | $1,585.52 | $22,703.64 |
| 19 | $8,394.60 | $7,229.03 | $1,165.57 | $15,474.61 |
| 20 | $8,394.60 | $7,674.91 | $719.69 | $7,799.70 |
| 21 | $8,046.04 | $7,799.70 | $246.34 | $0.00 |
Amortisation is the process of a loan balance declining to zero through scheduled payments. This calculator is schedule-first: it generates every month of the loan — payment, interest portion, principal portion and remaining balance — because the schedule is where the real behaviour of a loan lives. Early payments are mostly interest, late payments are mostly principal, and the rows show that crossover happening.
Extra payments are where the schedule becomes a tool instead of a report. Any amount you add on top of the required payment goes entirely to principal (no extra interest is charged on it), which lowers next month's interest, which frees more of the following payment for principal. The effect compounds: the calculator re-runs the whole schedule with your extra amount and reports the new payoff date and the interest saved against the original schedule, side by side.
The schedule assumes the rate stays fixed and extra payments are made every month from the start. A lump sum part-way through, a variable rate or missed payments all produce different rows — in those cases the honest approach is to run the calculator again with the balance, rate and remaining term as they stand after the change.
Every extra dollar reduces the balance immediately, and interest is charged on the balance every month that follows. On the $100,000 example, $100 extra a month saves $39,900.41 — far more than the $25,200 of extra payments themselves (100 × 252 months) — because each dollar removed early avoids years of interest charges at 6%.
No — on a standard fixed loan the required payment stays the same; extra payments shorten the term instead. That is exactly why they are so effective: the same payment is applied to a smaller balance, so more of it becomes principal each month and the loan ends early.
The Loan Calculator works out the payment and headline totals; this calculator is built around the month-by-month schedule itself and around extra payments. It answers 'when exactly will I be done, and what does paying more change?' rather than 'what is the payment?'
Yes — if a payment (with no extra) were smaller than that month's interest, the unpaid interest would be added to the balance and the loan would grow instead of shrinking; this is called negative amortisation. The standard payment formula is designed so this never happens on a normal loan: the payment always exceeds the first month's interest, the largest interest charge of the loan.
Yes. Some lenders apply overpayments against future scheduled payments unless instructed otherwise, which delays instead of reducing the balance. The savings shown here assume every extra amount goes straight to principal in the month it is paid — check your lender applies it that way, and check for any early-repayment charges before increasing payments.
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