Guide

Rule of 78: the old math that punishes early payers

You paid off your loan early to save on interest. Then the settlement figure arrives and the "savings" are much smaller than you expected. If your contract uses the Rule of 78, that disappointment is built into the formula — and understanding it takes about five minutes.

Where the name comes from

Take the numbers 12 down to 1 and add them: 12+11+10+…+2+1 = 78. That sum is the denominator of the whole method, hence "Rule of 78." For a 12-month loan, the total interest is divided into 78 parts. In month 1 the lender keeps 12/78 of the total interest. Month 2 keeps 11/78. By month 12 only 1/78 remains. The interest is front-loaded: you pay most of it early, whether or not you actually held the money that long.

The rebate formula

When you settle early, you are owed back the interest the lender "reserved" for the months you will no longer owe. Under Rule of 78 the rebate is:

Rebate = T × u × (u+1) ÷ [n × (n+1)]

where T is the total interest over the full term, n is the original number of monthly payments, and u is the number of payments remaining. Worked example from the standard case: total interest RM1,200, original term 12 months, settling with 6 months left. Rebate = 1,200 × 6 × 7 ÷ (12 × 13) = 1,200 × 42 ÷ 156 = RM323.08. You paid in roughly half the interest; you get back about 27% of it, not 50%.

Compare with a true reducing-balance loan, where the outstanding balance after half the payments reflects the actual principal still owed, and settling means paying exactly that. The gap between the two numbers is the cost of the Rule of 78 to you.

Why lenders like it (and regulators don't)

Rule of 78 is a pre-computer approximation from an era when interest was computed by hand. It was designed to approximate the declining-balance method, but it systematically overcharges early settlement: the front-loaded interest schedule means the "earned" interest always runs ahead of the true economic interest on the outstanding principal. Lenders discovered it made early payoff more profitable. Consumer regulators worldwide have restricted or banned it for consumer credit — the US banned it for mortgages in 1992 and for most consumer loans in 1996.

Where it shows up in Malaysia

In Malaysia the Rule of 78 has historically appeared in hire-purchase agreements (cars, motorbikes, equipment) and some personal financing products, rather than in conventional home loans, which use true reducing-balance amortisation. Hire-purchase is where it bites hardest: the front-loaded interest means selling a financed car in the first couple of years can leave you owing more than the car is worth. If your hire-purchase or personal financing contract mentions "Rule of 78", "78s", "sum of digits" or "pre-computed interest", that is this formula operating on your settlement figure.

What to do about it

Three practical moves. First, know which method your contract uses before you sign — ask directly and find the clause. Second, if you are planning early settlement on a Rule of 78 contract, settle in the later third of the term where the penalty is proportionally smaller, or settle at maturity and skip the game entirely. Third, always get the official settlement figure from the lender in writing before paying — the calculator here shows the estimate, the lender's statement is the bill, and the two can differ if your contract has different terms (lock-in periods, settlement fees, different rebate methods).

The early settlement calculator shows reducing-balance outstanding and Rule of 78 settlement side by side on your own numbers, so the difference is a number, not a guess.

This guide is general information, not financial or legal advice. Settlement terms are governed by your specific contract. Always obtain the official settlement figure from your financing provider before paying.