Add-On Rate vs Effective Interest Rate: What Your Loan Really Costs

A loan advertised as “1% per month” sounds like one of the cheapest deals around, but that add-on rate almost never equals what you actually pay. Once you compute the effective interest rate, the real cost is often close to double the number printed on the loan flyer.

What “add-on rate” actually means

An add-on rate is a simple, flat way lenders calculate interest. The formula is straightforward:

• Interest = Principal x Rate x Term

The catch is that this interest is computed once, on the full original principal, and then spread evenly across your installments — even though you are steadily paying that principal down every month. In a proper diminishing balance loan (the kind banks use for salary loans and most amortized loans), interest is recalculated each month only on the remaining balance. With add-on pricing, you keep paying interest as if you still owed the full amount on day one, all the way to the last payment.

This pricing style is common with financing companies, appliance and motorcycle installment plans, some cooperative loans, and many online lending apps operating in the Philippines. It is also why two loans that look similar on paper — “1% a month” versus “1.5% a month diminishing” — can cost very different amounts.

Why 1% a month is not really 1% a month

Because add-on interest is charged on the full principal for the entire term, your effective interest rate ends up roughly 1.8 to 2 times higher than the stated add-on rate for a typical monthly-amortized loan. The intuition is simple: on average, over the life of the loan, you only actually owe about half of the original principal (since you are paying it down every month), yet you are being charged interest as if you owed the full amount the whole time. That mismatch is where the extra cost hides.

A worked peso example

Say you borrow ₱50,000 for 12 months at an add-on rate of 1% per month.

• Interest = ₱50,000 x 1% x 12 months = ₱6,000
• Total to repay = ₱50,000 + ₱6,000 = ₱56,000
• Monthly installment = ₱56,000 ÷ 12 = ₱4,666.67

At first glance, ₱6,000 interest on ₱50,000 over a year looks like a 12% annual cost. But because you are paying down principal monthly while still being charged interest as though the full ₱50,000 remained outstanding, the effective monthly interest rate on this loan is closer to 1.85%, which annualizes to roughly 20–24% depending on how it is compounded. That is nearly double what the “1% per month” label suggests, and it is much closer to what you would pay on a diminishing-balance loan quoted at around 1.8% to 2% monthly.

Compare that to a diminishing balance loan for the same ₱50,000 at a true 1% monthly rate: your first month’s interest would be based only on ₱50,000, but by month six you would only be paying interest on whatever principal remains, which is significantly less than half the original amount by then. The add-on version never gives you that relief.

Add-on vs diminishing balance, side by side

• Add-on rate: interest fixed upfront on full principal, same peso amount of interest whether you are on payment 1 or payment 11.
• Diminishing balance: interest recalculated monthly on the outstanding balance, so the interest portion shrinks and the principal portion grows as you go.
• Result: for the same stated rate, add-on always costs more in effective terms, often by roughly 1.8x to 2x.

This is also why paying off an add-on loan early rarely saves as much as people expect — the interest was already baked in at the start, unlike a diminishing balance loan where early payoff meaningfully cuts future interest.

Where you will run into add-on pricing in the Philippines

Add-on rates show up often in appliance and gadget installment plans, motorcycle and vehicle financing, some cooperative and pawnshop-adjacent products, and certain online lending apps. Informal lenders, including some 5-6 arrangements, effectively function the same way — a flat charge per cycle on the original amount borrowed, which is precisely why 5-6 lending is notorious for being expensive once you convert it to an effective annual rate. Salary loans from banks or employers, on the other hand, are more commonly quoted on a diminishing balance basis, which is generally cheaper for the same nominal rate.

Before signing anything, always ask the lender directly: “Is this add-on or diminishing balance?” If they cannot answer clearly, treat that as a red flag rather than a technicality.

How to protect yourself

• Ask for the effective interest rate or the Truth in Lending Act disclosure, not just the advertised monthly rate.
• Convert any add-on offer to its rough effective rate before comparing it against other loans.
• Check the total peso amount you will repay, not just the percentage being quoted.
• If you are juggling multiple debts already, it may help to first sort out which ones to pay off debt first before taking on new borrowing.

If you are on the other side of the table — running or considering a small lending operation — understanding the gap between add-on and effective rates matters just as much; our guide on how to run a lending business in the Philippines covers how these numbers affect both borrowers and lenders. And if the real issue is simply keeping monthly cash flow steady enough to avoid loans altogether, a solid budget is usually the cheaper fix.

This article is for general education only and is not financial, legal, or lending advice. Loan terms vary by lender, so always read the disclosure statement and ask the lender directly for the effective interest rate before signing.

Frequently asked questions

Is add-on interest illegal in the Philippines?

No, add-on pricing itself is not illegal. However, lenders are generally required under the Truth in Lending Act to disclose the effective interest rate alongside any nominal or add-on rate, so you can compare offers fairly. If a lender refuses to disclose this, that is worth questioning before you borrow.

How do I quickly estimate the effective rate from an add-on rate?

A simple approximation for a loan paid in equal monthly installments is to roughly double the add-on rate. For longer terms the multiplier trends slightly below 2x, and for shorter terms it trends slightly above, but “close to double” is a safe rule of thumb for typical 6 to 24 month consumer loans.

Does paying an add-on loan early reduce the interest I owe?

Usually not by much, because the interest was calculated upfront on the full original principal for the full term rather than recalculated monthly on your remaining balance. Some lenders offer a partial rebate for early settlement, but it is rarely proportional to how early you paid, so always ask about the specific early payoff policy before assuming you will save money.