Debt
Stretching a loan lowers the payment and raises the total
Term length moves the monthly figure and the amount eventually handed over in opposite directions, because interest is charged for as long as the balance exists.
By Rosa Iglesias4 min read
Two numbers that move against each other
A loan is usually presented as a monthly payment, because that is the figure a borrower has to fit into a budget. It is also the figure that is easiest to make smaller, and the way to make it smaller is to spread the same borrowing over more months. Nothing about the amount borrowed changes; only the schedule does.
What changes with it is the total handed over by the end. Longer terms cost more in aggregate, and the relationship is reliable enough to treat as a rule: the payment and the total move in opposite directions when the term moves. A borrower shown two options with different terms is being shown a trade, even if only one side of it is on the page.
This is not a criticism of long terms, several of which are entirely sensible. It is an argument for seeing both numbers before choosing between them.
Why the total rises: interest is rent on time
Interest is charged on the balance outstanding, for as long as it is outstanding. That single sentence contains the whole mechanism. Two borrowers taking the same amount at the same rate will pay different totals if one clears the balance faster, because the second one keeps a larger balance in existence for longer.
Stretching a loan therefore does two things at once, both unhelpful for the total. Each payment is smaller, so less of it goes to reducing the principal in the early months. And the principal that remains sits there accruing for additional years that the shorter term would not have included.
It follows that the extra cost of a longer term is not a fee and cannot be negotiated away. It is the arithmetic consequence of borrowing the same money for a longer period, and it would exist even if every party to the transaction were entirely benevolent.
An illustration, with the sums shown
Take an illustrative loan of 10,000 at an illustrative fixed annual rate of 6%, repaid in equal monthly instalments. These figures are chosen to make the arithmetic legible; real rates and terms differ by country, by lender and by borrower.
Over three years the payment works out at roughly 304 a month, and the total repaid is about 10,950 — so around 950 of interest. Over six years the payment falls to roughly 166, which is a reduction of about 45%, and the total repaid rises to about 11,930. The interest has roughly doubled, to around 1,930.
That is the trade stated in numbers: a monthly figure almost halved, an interest bill almost doubled. Whether that is a good exchange is a real question with no automatic answer, and it depends on what the household would do with the difference each month.
The trade gets worse at the long end
The relationship is not linear, which is the part most likely to catch someone out. Each additional year removes less from the monthly payment than the year before it, while adding a full year of interest on whatever balance is still outstanding. The reductions shrink; the additions do not.
So the first extension of a term usually buys a great deal of monthly relief for a modest increase in the total, and the fourth or fifth buys very little for a considerable increase. A borrower deciding between three years and four is in a different position from one deciding between eight and nine, even though both are adding twelve months.
Anyone comparing options can see this directly by asking for the total repayable at each term rather than only the monthly figure. The pattern shows up immediately, and it is the clearest single piece of information in the comparison.
When the longer term is nonetheless the better choice
A lower payment is not merely a comfort. It reduces the chance of missing a payment, and the cost of missed payments — fees, damage to a credit record, and in some cases the loss of whatever secured the loan — can dwarf the extra interest of a longer term. Affordability with room to spare is worth paying for.
A longer term can also be right when the money freed each month is doing something valuable: maintaining a buffer, covering an unavoidable cost, or servicing a more expensive debt elsewhere. Those are legitimate uses of the difference. Spending it without noticing is what turns the trade into a straightforward loss.
Two details change the picture and are worth checking on any specific agreement: whether early repayment is permitted without a penalty, which lets a borrower take the safety of a long term and the cost of a short one, and whether the rate is fixed for the whole period. Both vary widely, and both are matters for the agreement and a regulated adviser rather than a general article.
Common questions
Is it always cheaper to take the shortest term I can afford?
Cheaper in total interest, yes, almost always. But the shortest affordable term leaves no margin, and a payment that is manageable in a good month may not be in a difficult one. Many people deliberately take a slightly longer term and overpay when they can, where the agreement allows it.
Does overpaying actually help on a long loan?
Where it is permitted without penalty, considerably — and most on an early overpayment, because the money removes both that part of the balance and all the interest it would have generated over the remaining years. The same amount paid in the final year saves very little.
Why do lenders advertise the monthly payment rather than the total?
Because it is the figure most borrowers use to decide affordability, and a smaller one makes a loan look more comfortable. That is not necessarily deceptive, since the payment genuinely is what has to be found each month, but it does mean the total repayable often has to be asked for rather than read.
Rosa has written about spending, saving, debt for most of the last decade and is unreasonably interested in the detail nobody else checks.
