What this calculator answers
Most loan tools, including the Loan Calculator, answer a single question: given an amount, an APR and a term, what is the fixed monthly payment. This one asks a different question: given that same loan, what changes if the payments land more often than once a month, and does paying more often actually pay the loan off faster, or only rearrange the same yearly total into smaller pieces. It does not add extra lump-sum overpayments on top of the schedule; a calculator built specifically for extra payments belongs alongside it in this cluster and covers that separately, so this page can stay focused on frequency alone.
Every result below comes from the same three numbers entered once: the amount borrowed, the APR and the term. Switching the frequency toggle from monthly to fortnightly or weekly, and, for those two, switching between "true" and "accelerated", recalculates the payment, the payoff time and the total interest without touching anything else.
The periodic rate this calculator uses
A monthly payment turns an annual percentage rate into a monthly one by dividing by 12; that is exactly what the Loan and Amortization calculators do, and what the monthly row here does too. Fortnightly and weekly schedules need the same annual rate turned into a fortnightly or weekly one, and this calculator divides by the number of pay periods in a year instead: APR ÷ 26 for fortnightly, since a year holds 26 fortnights, and APR ÷ 52 for weekly. That simple division, rather than a compounded equivalent rate, is the convention used by most published biweekly and weekly repayment calculators, and it lines up with the monthly convention already used across this site, so the same loan behaves consistently whichever frequency is chosen.
On the calculator's own defaults, £250,000 at 5.5% APR over 25 years, that formula returns a monthly payment of £1,535.22, a fortnightly rate of 5.5 ÷ 26 ÷ 100, and a weekly rate of 5.5 ÷ 52 ÷ 100. Everything below builds on those same three figures.
Two different things both get called "fortnightly"
This is the whole reason the page exists: "pay fortnightly" can mean two genuinely different schedules, and only one of them changes how quickly a loan clears.
True fortnightly solves for a fortnightly payment that repays the loan over exactly the same term, just split into 26 instalments a year instead of 12. On the defaults above that payment is £708.16 a fortnight. Because the total paid across a year barely moves, so does the total interest: the loan still clears in 25 years, and the saving over the plain monthly schedule is £264 across the entire 25 years, real, but easy to miss.
Accelerated fortnightly is a different instruction entirely: pay exactly half of the original monthly payment every two weeks, £767.61 in this example, rather than solving for a new payment at all. Fifty-two weeks contain 26 fortnights, so 26 half-payments a year add up to 13 full monthly payments, one more than the usual 12. That extra payment goes straight onto the balance, and on these numbers it clears the loan in 21 years and 3 months rather than 25, saving £36,355 in interest, more than a hundred times the true-fortnightly saving, for the same "pay fortnightly" instruction worded slightly differently.
Weekly schedules split the same way: true weekly solves a payment for 52 instalments a year that keeps the loan on its original 25-year course (£353.99 a week here, saving £377 in interest), while accelerated weekly pays a quarter of the monthly payment every week, £383.80 in this example, which is again 52 quarter-payments adding up to 13 monthly payments and the same roughly 21-year-3-month payoff as accelerated fortnightly. The comparison table above runs all five schedules side by side on the same loan so the gap is visible rather than assumed.
Where the extra payment actually comes from
Run the arithmetic on the accelerated schedule directly: 26 fortnightly payments of £767.61 add up to about £19,958 a year, against 12 monthly payments of £1,535.22 adding up to about £18,423 a year. The difference, around £1,535, is not a rounding artefact; it is one extra monthly payment, contributed entirely because a year happens to hold 26 fortnights rather than the 24 half-months that 12 payments would imply. That extra payment lands on the balance early and often, which is why it saves far more interest than its size alone would suggest: every pound taken off the balance sooner stops earning interest for every remaining period of the loan.
Nothing about the fortnight or the week as a unit of time is doing any of that work. A monthly schedule that simply added a 13th payment once a year would save an almost identical amount of interest; the fortnightly rhythm is only the vehicle that makes an extra payment happen automatically rather than requiring a deliberate decision each year.
Is switching worth it
Accelerated schedules suit anyone actually paid fortnightly or weekly, since lining repayments up with pay day turns the extra payment into something that happens by itself rather than something to remember. They also suit anyone who can comfortably afford roughly one-twelfth more a year and wants that commitment locked into the schedule itself rather than left as an occasional overpayment. True fortnightly or weekly suits a different, narrower case: matching a repayment date to a pay date without taking on a bigger yearly total, worth doing for the convenience, not for any meaningful saving.
Two honesty checks matter before switching. First, not every lender offers a genuinely non-monthly schedule: some "biweekly payment plans", often run by a third party rather than the lender itself, simply collect money more often and hold it, still forwarding a single payment to the loan on its original monthly date, which behaves exactly like the plain monthly schedule underneath despite the more frequent withdrawals. Ask the lender directly whether extra fortnightly or weekly payments are applied to the balance as they arrive, and whether any fee applies, before assuming either true or accelerated is actually available. Second, interest on most loans accrues daily against the outstanding balance, so even the true schedules above are not doing literally nothing: they nudge a little interest off the top by paying slightly sooner, on average, than a single monthly date would. The gain from that alone is real but small, a few hundred pounds across a full term in the example above, which is exactly why the accelerated schedule, built on paying more rather than paying differently timed, is the one that actually moves the payoff date.
Questions people ask
Does paying fortnightly instead of monthly pay off a loan faster by itself?
Only if it means paying more per year. A "true" fortnightly schedule that keeps the same total paid annually as monthly barely changes the payoff date at all. An "accelerated" fortnightly schedule, half the monthly payment every two weeks, pays 13 monthly payments a year instead of 12 and does shorten the loan meaningfully, because it adds a real extra payment, not because fortnights work differently to months.
How much does true fortnightly actually save?
Very little in most cases. On £250,000 at 5.5% over 25 years it saves around £264 in total interest across the entire term, because slightly more frequent payments trim a small amount of daily-accruing interest without adding any extra money to the loan. Worth doing if it lines up with pay day; not worth relying on for a meaningfully earlier payoff.
Will my lender let me pay fortnightly or weekly?
Not automatically. Some lenders support a genuine non-monthly schedule directly; others only offer monthly billing and rely on a third-party "biweekly payment" service that collects money more often but still forwards a single payment to the loan monthly, which behaves like the plain monthly schedule regardless of how often money leaves your account. Ask the lender in writing how and when extra payments are actually applied before assuming either schedule is available.
Is accelerated fortnightly the same as overpaying?
The effect is the same, an extra payment a year reducing the balance faster, but the mechanism differs. Overpaying is a deliberate lump sum or top-up on top of a normal schedule; accelerated fortnightly builds the extra payment into the schedule itself by paying half the monthly amount every two weeks. A calculator built specifically around lump-sum and top-up overpayments covers that side of the question in more depth.
Why is the weekly saving almost identical to the fortnightly saving?
Because both accelerated schedules add up to the same extra amount a year: 52 quarter-payments a week or 26 half-payments a fortnight both come to 13 monthly payments' worth of money, paid slightly more often in the weekly case. The extra annual payment, not the exact rhythm it arrives in, is what drives the saving, so the two land within a few pounds of each other.
Does this work for a mortgage as well as a personal loan?
The arithmetic is the same fixed-repayment formula behind most mortgages and instalment loans, so the frequency comparison here applies equally to either. Mortgages often fix the rate for an initial period only and involve larger sums over longer terms, which this calculator handles, though a lender's specific overpayment rules and any early repayment charges still need checking directly with them.
These figures are estimates for a simple fixed-rate loan with the periodic-rate convention described above, not financial or lending advice. What a lender actually offers, including whether non-monthly schedules are genuinely available and how quickly extra payments are applied, depends on the credit agreement, so check with the lender directly before changing how you pay.