Loan Calculator Widget

Add a loan calculator that handles more than monthly payments. Readers choose monthly, every-two-weeks or weekly payments, add an optional extra payment and see how much interest and time it saves, with a yearly schedule.

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<iframe src="https://a2z.tools/embed/w/loan-calculator" title="Loan Calculator by A2Z Tools" width="100%" height="800" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.

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How it works

The level payment comes from the shared A2Z time-value-of-money engine (XtFin.pmt). The widget then runs the loan payment by payment: interest is charged on the outstanding balance at the annual rate divided by the number of payments a year, and the rest of each payment, plus any extra, reduces the balance. Running it twice, with and without the extra payment, gives the exact interest and time saved rather than an approximation. Biweekly means 26 payments a year at APR / 26 - a true every-two-weeks loan - and weekly means 52 at APR / 52. The final payment is whatever clears the remaining balance, so it is usually a little smaller than the others, and the yearly table groups payments into years of 12, 26 or 52 payments.

Calculation method

  • Payment = P x i / (1 - (1 + i)^-n)
  • P = loan amount; i = annual rate / 100 / payments per year (12, 26 or 52); n = term in years x payments per year, rounded to a whole payment
  • Each period: interest = balance x i; balance falls by payment + extra - interest; the last payment is capped at the balance
  • Interest saved = interest without the extra payment - interest with it; time saved = difference in the number of payments
  • At 0% interest, payment = P / n
  • Rounding: balances are carried unrounded; money is displayed to 2 decimals and the yearly table in whole units

Worked examples

Car loan paid monthly

Inputs: 25,000 at 7.5% for 5 years, monthly, no extra

Result: Payment 500.95 for 60 payments; total interest 5,056.92; total repaid 30,056.92

The standard amortising payment - the baseline for the other two examples.

Same loan with 100 extra each month

Inputs: 25,000 at 7.5% for 5 years, monthly, extra 100

Result: Total interest 4,043.31; paid off in 4 years 1 month; interest saved 1,013.61; time saved 11 months

Every extra payment goes straight to principal, so later interest is charged on a smaller balance.

Same loan paid every two weeks

Inputs: 25,000 at 7.5% for 5 years, biweekly

Result: Payment 230.89 for 130 payments; total interest 5,015.41

True biweekly scheduling saves only 41.51 of interest; the big saving from 'biweekly' plans comes from the extra thirteenth monthly payment.

Limitations

  • Uses a fixed nominal rate split evenly across periods; loans that accrue interest daily (actual/365) will differ by small amounts.
  • Does not model fees, APR, insurance, prepayment penalties or payment holidays.
  • The extra payment is the same every period; one-off lump sums are not supported.
  • Does not know a lender's rule for how extra payments are applied - some hold them until the next due date, and some apply them to future instalments instead of principal unless asked.
  • Terms are whole payment periods; odd first periods, deferred first payments and balloon or interest-only loans are not supported.

Where publishers use it

  • A credit union's page explaining how biweekly payments shorten a loan
  • Personal-finance posts on whether to overpay a car or personal loan
  • Equipment-finance and small-business lending sites quoting weekly repayments
  • Budgeting courses that show how much of a payment is interest
  • Payroll-deduction lenders and employers offering salary advances repaid each pay cycle
  • Solar-panel, home-improvement and medical-financing pages quoting a per-paycheque or per-month cost

Questions

Why is the biweekly payment not exactly half the monthly one?

Each biweekly payment is calculated for 26 payments a year at a rate of APR / 26, so the loan is repaid on its own schedule: 25,000 at 7.5% over 5 years is 230.89 every two weeks against 500.95 a month. Lenders that simply take half the monthly payment every two weeks collect 13 monthly payments a year and pay the loan off early; model that by entering the difference as an extra payment.

How is the interest saved by an extra payment worked out?

The widget runs the full schedule twice - once with the level payment only and once with the extra added each period - and subtracts the two interest totals. On 25,000 at 7.5% for 5 years, an extra 100 a month saves 1,013.61 of interest and 11 months.

Does it include fees or insurance?

No. It covers principal and interest only. Origination fees, payment-protection insurance and prepayment penalties vary by lender and are not included, so compare lenders on their disclosed APR as well.

Can I preset weekly payments for my site?

Yes. Set v_freq=weekly (or biweekly) with v_amount, v_rate and v_term in the embed code; readers can still change them. 25,000 at 7.5% over 5 years is 115.38 a week for 260 weeks.

How do I model a 'half-payment every two weeks' plan?

Choose biweekly and enter the gap between half the monthly payment and the true biweekly payment as the extra. For 25,000 at 7.5%, half of 500.95 is 250.48, so the extra is 19.59: the loan is gone after 118 payments, about 4.5 years, saving 488.71.

Why is the APR on my offer higher than the rate I entered?

An annual percentage rate folds origination fees and some other charges into a yearly cost, so it is usually above the note rate that drives the payment. Enter the note rate here for the payment, and use the lender's APR to compare offers.

Is a weekly schedule cheaper than monthly?

Only slightly on the same nominal rate: 25,000 at 7.5% over 5 years costs 4,997.60 of interest weekly, 5,015.41 biweekly and 5,056.92 monthly, because each payment starts reducing the balance a little sooner.

How do I use it for a car purchase with a trade-in?

Subtract the deposit, the trade-in value and any manufacturer rebate from the price, add any taxes or dealer fees you are financing, and enter the result as the loan amount. 18,500 financed at 6.9% over 4 years is 442.15 a month with 2,723.09 of interest.

What is the Rule of 78s and does the widget use it?

It is an old method for precomputed-interest loans that books more of the interest in the early months, so paying off early saves less. The widget uses the actuarial (simple-interest amortising) method, where interest is always charged on the balance actually owed.

Is a longer term worth the lower payment?

It lowers each payment but raises the total cost. 40,000 at 9% over 7 years is 643.56 a month with 14,059.30 of interest; the same loan over 5 years costs more each month but much less interest. Enter both terms to compare them side by side.

What is a balloon or residual-value loan and can I model it?

A balloon loan leaves a large lump sum, the residual, due with the final payment - common in car PCP and some commercial leases. This widget amortises to zero, so it overstates the regular payment for a balloon deal; subtract the discounted residual from the amount for a rough idea only.

Why does my statement show slightly different interest?

Many consumer lenders accrue interest daily on the actual days between payments, so a 31-day month costs a little more than a 28-day one. The widget splits the nominal rate evenly across periods, which is the textbook annuity convention.

Sources

  1. EMI Calculator (assets/calc/dcutils.js mortgagePayment) - SEBI Investor website, Securities and Exchange Board of India . Same level-payment formula with the rate divided by the number of payments. Checked 2026-10-01.
  2. What is amortization and how could it affect my loan? - Consumer Financial Protection Bureau (US) . Interest on the outstanding balance; why extra principal payments reduce later interest.

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools Loan Calculator
https://a2z.tools/embed/loan-calculator

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