Interest saved and months shaved off by paying extra each month.
Interest saved
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Months shaved off
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Interest without extra
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Interest with extra
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Where the saving actually comes from
Paying extra on a loan feels like it should help, but the mechanism is worth understanding because it changes how you use this tool. Your regular monthly amortization is fixed and already covers that month's interest plus a sliver of principal. Anything you add on top has only one job: it knocks down the principal directly. A smaller principal means less interest charged next month, and the month after, all the way to the end. The saving compounds in your favour.
This calculator runs your loan twice. Once at the normal payment, and once at the normal payment plus your extra amount, amortising each until the balance hits zero. The difference between the two interest totals is what you save, and the difference in how many months each takes is the time you shave off. It is a clean before-and-after comparison rather than a single projection.
Timing beats size
The single most useful judgement here is that early extra payments are worth far more than late ones. An extra peso paid in the first year removes interest for the entire remaining term, while the same peso paid near the end removes almost nothing because there is little term left for it to work over. If you come into a bonus or a 13th-month payment, putting it against the loan early in its life is where prepayment earns its keep.
Note also that this tool keeps the same monthly payment and simply finishes the loan sooner. That is different from asking your lender to recompute a lower monthly payment over the original term, which lowers your bill each month but saves far less interest overall. Shortening the term is almost always the cheaper path if you can sustain the higher outflow.
PHP 3,000 extra a month on an PHP 800,000 balance
Take the values the tool loads: an PHP 800,000 balance at 10 percent a year with 60 months remaining, and you decide to add PHP 3,000 to each payment. The base amortization is about PHP 16,998 a month. Adding PHP 3,000 lifts it to roughly PHP 19,998. Here is the before-and-after.
| Measure | No extra | With extra |
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The chart compares the two interest totals. The taller bar is the cost of paying the minimum, and the shorter teal bar is the cost after prepaying.
Check the pre-termination clause first
Here is the practical catch that the headline saving can hide. Many Philippine lenders, especially on fixed-rate loans, charge a pre-termination or prepayment fee, often a percentage of the amount you pay ahead. If that fee is larger than the interest you would save, prepaying loses money. Before you commit, find the prepayment clause in your loan agreement and run the numbers: compare the interest saved this tool reports against the fee your lender quotes. If the saving comfortably beats the fee, prepay. If it is close, the certainty of being debt-free sooner may still tip it, but go in with eyes open. This is a contract question, so confirm the exact fee with your lender.
Is it smarter to prepay or to invest the extra money?
Compare the loan rate with what you could reliably earn after tax. Prepaying a loan at 10 percent is a guaranteed, risk-free return equal to that rate, which is hard to beat with a safe investment once you account for tax on the gains. If your loan rate is high, prepaying usually wins. If the loan is cheap and you have a high-conviction investment, the maths can flip. Clear high-interest debt first, build an emergency buffer, then weigh prepaying cheaper debt against investing.
What if I cannot commit to extra every single month?
You still benefit from occasional lump sums. This tool models a steady extra each month, but in practice a one-off payment from a bonus, applied early and directed to principal, also cuts the balance the interest is charged on. Ask your lender to confirm that ad hoc payments reduce principal rather than just sitting as advance amortization, because the saving depends on the balance actually falling.