A year-by-year view of the accelerated biweekly schedule, showing how much principal and interest you pay each year and the balance that remains. Notice how the balance falls faster than a standard monthly loan.
Year
Principal paid
Interest paid
Ending balance
Year 1
5,117
20,830
294,883
Year 2
5,487
20,459
289,396
Year 3
5,885
20,062
283,511
Year 4
6,311
19,636
277,200
Year 5
6,768
19,179
270,432
Year 6
7,258
18,689
263,174
Year 7
7,783
18,163
255,391
Year 8
8,347
17,600
247,044
Year 9
8,951
16,995
238,093
Year 10
9,599
16,347
228,493
Year 11
10,295
15,652
218,199
Year 12
11,040
14,907
207,159
Year 13
11,839
14,108
195,320
Year 14
12,697
13,250
182,623
Year 15
13,616
12,331
169,007
Year 16
14,602
11,345
154,406
Year 17
15,659
10,288
138,746
Year 18
16,793
9,154
121,954
Year 19
18,009
7,938
103,945
Year 20
19,313
6,634
84,632
Year 21
20,711
5,236
63,921
Year 22
22,211
3,736
41,710
Year 23
23,819
2,128
17,891
Year 24
17,891
471
0
Estimates only — not financial, tax, or professional advice.
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What it calculates: Biweekly Payment, Interest Saved, Years Saved, Biweekly Payoff Time.
Updated 5 June 2026 · Transparent assumptions
Twenty-six half-payments is thirteen monthly payments a year
The saving does not come from paying fortnightly. It comes from the fact that a year contains twenty-six fortnights but only twelve months, so halving the monthly payment and paying it every two weeks quietly pays one extra monthly instalment every year.
That is the entire mechanism, and it is worth being clear about because it means the biweekly schedule is not a clever financing trick. It is a one-thirteenth overpayment with a calendar wrapped around it, and an equivalent result comes from simply paying one extra instalment a year.
Every extra rupee lands on principal, and principal is what charges interest
A scheduled payment is split between interest due and principal repaid. The extra thirteenth payment has no interest attached to it, so all of it reduces the balance — and a smaller balance charges less interest next period, which leaves more of the following payment to attack the principal again.
This is why the effect is larger than one-thirteenth. On a typical long mortgage the schedule finishes several years early rather than one year in thirteen early, and the calculator reports both the years saved and the interest saved so the size of that compounding is visible.
Some lenders hold the money instead of applying it
Not every lender accepts biweekly payments, and some that do hold each half-payment and apply the pair only when a full monthly instalment has accumulated. That arrangement produces none of the saving modelled here, because the balance is not reduced any earlier than it would have been.
Third-party biweekly services exist and typically charge a setup fee plus a per-payment fee. Since the identical result is available by paying one extra instalment a year directly, those fees are usually pure cost — confirm how your own lender applies partial payments before paying anyone to arrange it.
A fixed rate, no fees, and a lender that applies payments immediately
The projection assumes the rate never moves, every payment arrives on time for the whole term, and each one is credited against the balance the day it is received. A variable-rate loan invalidates the comparison, because the monthly baseline it is measured against would itself have changed.
It also ignores prepayment penalties, which some loans apply to early repayment, and it says nothing about whether the money is better used elsewhere. Clearing a 7% mortgage early is a guaranteed 7% return, which is a strong argument — but not automatically the strongest one available.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.
Results are estimates based on the figures you enter and standard formulas. Rates, fees, taxes, and lender terms vary and change over time, so confirm important numbers with your lender or a qualified professional. This is educational information, not financial advice.
Published the calculator with its formula, worked example, assumptions, limitations and a bespoke guide, and added an automated formula test suite covering it.
Tested the biweekly amortisation against an independently run schedule, and checked the monthly baseline it is compared with separately.
Tested that the biweekly schedule always finishes earlier than the monthly one and that the interest saved is the difference between the two totals.
Show it to your clients, not just tell them
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