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Biweekly Mortgage Calculator

Compare a standard monthly repayment mortgage with a biweekly payment illustration. A biweekly plan makes 26 half-payments a year—equivalent to 13 monthly-payment amounts—when extra amounts are applied to the mortgage balance.

Mortgage details

20% of property price
%
Enter the annual interest rate shown in your mortgage illustration or example scenario.
years
Enter the number of whole years for the mortgage term.

How the biweekly illustration works

The standard monthly repayment is divided by two and paid every two weeks. There are 26 biweekly payments a year, equal to 13 monthly-payment amounts rather than 12. This illustration assumes each biweekly payment is applied to the mortgage balance.

Loan amount
£600,000
Standard monthly repayment
£3,595.49 per month
Biweekly payment
£1,797.74 every two weeks
Estimated earlier repayment with biweekly payments
3 years 8 months earlier

The illustration makes 26 half-payments a year, equal to 13 monthly-payment amounts.

Annual amount modeled: £43,146 with monthly repayments and £46,741 with the biweekly illustration.

Standard monthly repayment schedule compared with the modeled biweekly schedule
MetricMonthly repaymentsBiweekly illustration
Payment amount£3,595.49 per month£1,797.74 every two weeks
Payments per year1226 half-payments
Amount paid each year£43,146£46,741
Estimated payoff time25 yearsabout 21 years 4 months
Estimated total interest£478,646£397,715
Interest difference—£80,931 less interest in this illustration
Estimated annual mortgage balance and interest comparison
YearMonthly balanceBiweekly balanceMonthly interestBiweekly interestBalance difference
1£588,070£584,330£31,216£31,072£3,740
2£575,498£567,818£30,574£30,229£7,680
3£562,250£550,417£29,898£29,341£11,833
4£548,290£532,081£29,185£28,405£16,209
5£533,578£512,758£28,435£27,419£20,820
6£518,076£492,396£27,643£26,379£25,680
7£501,740£470,939£26,810£25,284£30,801
8£484,525£448,328£25,931£24,130£36,197
9£466,384£424,501£25,005£22,914£41,883
10£447,268£399,393£24,030£21,633£47,875
11£427,123£372,934£23,001£20,282£54,190
12£405,896£345,052£21,918£18,859£60,844
13£383,526£315,671£20,776£17,360£67,856
14£359,954£284,709£19,573£15,780£75,245
15£335,113£252,082£18,305£14,115£83,031
16£308,937£217,701£16,970£12,360£91,236
17£281,353£181,470£15,562£10,511£99,883
18£252,285£143,291£14,078£8,562£108,994
19£221,654£103,059£12,515£6,509£118,596
20£189,376£60,662£10,867£4,345£128,714
21£155,361£15,986£9,132£2,065£139,376
22£119,518£0£7,302£161£119,518
23£81,746Repaid£5,374Repaid£81,746
24£41,944Repaid£3,343Repaid£41,944
25£0Repaid£1,202Repaid£0

How to use this calculator

Pick your currency, then enter the property price, your deposit, the annual interest rate and the mortgage term in whole years. The calculator works out the standard monthly repayment from those figures, then models a biweekly schedule that pays half that amount every two weeks.

The result shows how much sooner the modeled biweekly schedule clears the balance, the monthly and biweekly payment amounts, and the amount paid each year on each schedule. The Breakdown tab lists the annual balance and interest for both schedules, the Chart tab plots the two balance paths, and the Summary tab lists the assumptions used.

This is a neutral illustration, not mortgage advice. It does not recommend a payment plan, promise savings, assess affordability, predict whether a lender will accept biweekly payments, calculate fees or early-repayment charges, or forecast interest rates.

How biweekly mortgage payments are calculated

The calculator first works out the standard monthly repayment from the loan amount, annual interest rate and mortgage term. It then models payments of half that monthly amount every two weeks, using 26 payment periods a year.

  • P — loan amount, the property price minus the deposit
  • r — the annual interest rate you enter, as a decimal (5.25% is 0.0525)
  • T — the mortgage term in whole years
  • im = r ÷ 12 — the monthly periodic interest rate
  • nm = 12 × T — the number of monthly payments in the term
  • M — the standard contractual monthly repayment
  • B = M ÷ 2 — the modeled biweekly payment
  • nb = 26 × T — the number of biweekly payments in the term
  • ib — the modeled compounding-consistent two-week periodic rate
  • Qt — the balance remaining at the end of period t, starting from Q₀ = P
M = P × im(1 + im)ⁿᵐ ÷ ((1 + im)ⁿᵐ − 1)
  • P = property price − deposit
  • im = r ÷ 12
  • nm = 12 × T
  • If r = 0, M = P ÷ nm
  • B = M ÷ 2
  • 26 × B = 13 × M
ib = (1 + r ÷ 12)¹² ⁄ ²⁶ − 1
  • biweekly interestₜ = Qₜ₋₁ × ib
  • biweekly paymentₜ = min(B, Qₜ₋₁ + biweekly interestₜ)
  • Qₜ = Qₜ₋₁ − (biweekly paymentₜ − biweekly interestₜ)

For each period, interest is charged on the outstanding balance, and the payment is reduced on the final period so the balance cannot go below zero. The monthly schedule uses imover 12 periods a year; the biweekly schedule uses ib over 26 periods a year. The annual figures shown in the table and chart are the raw period-level results aggregated into schedule years.

The biweekly periodic rate is a compounding-consistent illustration. Mortgage lenders and servicers can use different interest-calculation and payment-processing methods, so actual lender figures may differ.

At a 0% interest rate, M is simply P ÷ nm, both schedules have no interest, and the biweekly schedule can still finish earlier because 26 half-payments add up to 13 monthly-payment amounts a year.

Selecting a currency changes the labels and number formatting only. It does not convert amounts using exchange rates.

Biweekly versus twice-monthly payments

Biweekly means every two weeks: 26 half-payments a year. Twice-monthly payments are 24 half-payments a year and normally equal 12 monthly payments. This calculator models a biweekly schedule, not a twice-monthly schedule.

Frequently asked questions

What is a biweekly mortgage payment?

A biweekly mortgage payment is half the standard monthly repayment, paid every two weeks instead of once a month. Because a year contains 26 two-week periods, a biweekly schedule makes 26 half-payments — the same as 13 full monthly-payment amounts. This calculator models that schedule and compares it with a standard monthly repayment mortgage. It is an illustration of the arithmetic, not a payment plan offered by a lender.

Why are there 26 biweekly payments in a year?

There are 52 weeks in a year, and 52 divided by 2 is 26, so paying every two weeks means 26 payments a year. Twelve of those 26 half-payments cover the equivalent of six monthly payments; the remaining 14 cover another seven — so 26 half-payments add up to 13 monthly-payment amounts, one more than the 12 made on a monthly schedule.

How is biweekly different from twice-monthly?

Biweekly means every two weeks, which is 26 payments a year. Twice-monthly (semi-monthly) means twice each calendar month — on the 1st and 15th, for example — which is 24 payments a year and normally adds up to exactly 12 monthly payments. A twice-monthly schedule pays the same total per year as a monthly one; a biweekly schedule pays the equivalent of one extra monthly payment. This calculator models a biweekly schedule, not a twice-monthly schedule.

Why does the annual amount differ from monthly repayments?

On a monthly schedule you make 12 payments of M, so you pay 12M in a year. On the modeled biweekly schedule you make 26 payments of M ÷ 2, so you pay 26 × (M ÷ 2) = 13M in a year. The extra 13M − 12M = M is one whole monthly-payment amount. The modeled difference in payoff time and interest comes from paying that extra amount each year, not from the change in payment timing on its own.

Does my lender apply biweekly payments immediately?

Not necessarily. Some lenders and servicers credit each half-payment to the mortgage balance as it arrives; others hold half-payments in a separate account and only apply a full monthly payment once both halves are received, which changes the interest effect. Some offer a formal biweekly programme, sometimes for a fee, and some do not accept biweekly payments at all. This calculator assumes each biweekly payment is applied to the balance when made. Check your mortgage offer and lender terms for how your payments would actually be handled.

Why might my lender’s figures differ?

The calculator uses one constant interest rate and a compounding-consistent two-week periodic rate. Real lenders use their own day-count and rounding conventions, may calculate interest daily or monthly, and may apply payments on set dates rather than immediately. Your rate is also likely to change when a fixed, tracker or discounted period ends. Treat the output as a rough illustration of the arithmetic, not a statement of what your lender will do.

Are fees or early-repayment charges included?

No. The illustration excludes arrangement and product fees, any charge for a lender’s biweekly programme, early-repayment charges, overpayment allowances, insurance, taxes and other costs. Some mortgages limit how much you can overpay in a year or charge an early-repayment charge for clearing the balance early, and paying the equivalent of 13 monthly payments a year is a form of overpayment. Your mortgage offer and lender’s rules determine whether that applies.

Does changing currency convert the mortgage amount?

No. Selecting a currency changes the currency symbol and number formatting on every field and result and nothing else. The property price, deposit, loan amount, payments, schedule and payoff durations keep the same nominal numbers — 600,000 stays 600,000 whether it is shown as pounds, dollars or euros. There is no exchange-rate conversion.