Weekly Loan Amortization Calculator and Payment Schedule

This weekly loan amortization calculator estimates your level payment for a fixed-rate loan when payments are made every week, then shows total paid and total interest over the stated term. Enter the loan amount, annual APR, and term in years; the result assumes 52 equal weekly payments per year.

Formula

The calculator uses a standard level-payment amortization formula, adapted to weekly periods. It converts the annual percentage rate to a weekly rate by dividing by 5,200, and treats the number of payments as 52 times the term in years:

Weekly payment = P × r / [1 − (1 + r)⁻ⁿ]

• P is the starting loan principal, in dollars.
• r is the rate per weekly period: APR ÷ 5,200, where APR is entered as a percentage.
• n is the number of weekly payments: years × 52.

Total interest is calculated as the weekly payment, rounded to cents, multiplied by the number of payments, minus the original principal: total interest = weekly payment × n − P. Because payments are rounded before this total is computed, small differences from an unrounded mathematical schedule can occur.

Worked Example

Using the defaults—$20,000 principal, 8% annual APR, and a five-year term—the model has 260 weekly payments and a weekly rate of 0.08 ÷ 52, or approximately 0.00153846.

1. Set P = $20,000, r = 0.08 ÷ 52, and n = 5 × 52 = 260.
2. Apply the payment formula: $20,000 × (0.08 ÷ 52) ÷ [1 − (1 + 0.08 ÷ 52)⁻²⁶⁰].
3. The unrounded weekly payment is approximately $99.33; rounded to cents, the calculator displays $99.33 per week.
4. Total interest using that displayed payment is $99.33 × 260 − $20,000 = $5,825.80.

Assumptions

• The interest rate is fixed for the entire term.
• Payments are equal and made once per week, with the first payment one weekly period after the loan begins.
• Interest accrues at a weekly rate calculated as APR divided by 52; this is equivalent to using APR / 12 as a monthly rate only for a monthly schedule, not this weekly schedule.
• Fees, taxes, insurance, PMI, escrow, late charges, and any lender-specific payment rules are not included.

How Weekly Amortization Works

Amortization means each scheduled payment covers interest accrued for a period and reduces principal by whatever remains. Early in repayment, the outstanding balance is larger, so more of each payment goes toward interest. As the balance falls, the interest portion generally shrinks and the principal portion grows. With an unchanged rate and on-time level payments, the balance is intended to reach zero at the end of the modeled term.

Weekly payment frequency does not mean the payment is simply one quarter of a monthly payment. The payment size must be recalculated for the number and timing of periods. This calculator uses 52 weekly periods per year, so a five-year term contains 260 payments. A lender may use a different day-count method, payment date convention, or rounding approach; the contract and payment schedule control the actual amounts.

When to Use the Estimate

Use this calculation to understand the approximate weekly cash outflow and the interest implied by a fixed-rate, fully amortizing schedule. It can also help compare schedules mathematically when the principal, APR, and total length are held constant. The APR must be the rate appropriate to the lender’s calculation, not a monthly rate or a number typed as a decimal. For example, enter 8 for 8%, not 0.08.

Take the actual amount financed, quoted APR, and repayment term from the lender’s current disclosure or loan documents. If the APR includes charges or the lender calculates interest daily, the calculator’s simplified conversion will not reproduce the lender’s exact schedule. The displayed result is a model, not a quote or an approval estimate.

Weekly Versus Biweekly and Monthly Payments

Weekly payments occur 52 times a year. Biweekly payments occur every two weeks, or 26 times a year, while monthly payments occur 12 times a year. These schedules are not interchangeable: the timing and number of payments affect how quickly principal is reduced and how much interest accrues between payments. A “weekly” payment is also not the same as paying a monthly amount divided by four, because there are 52 weeks—not 48—in a year.

Some payment plans describe weekly or biweekly withdrawals as an alternative collection schedule for a monthly obligation. Their treatment of partial payments, posting dates, and any fees can differ from a loan whose contract itself requires weekly installments. Check how payments are credited before comparing a lender’s schedule with this estimate.

Common Sources of Differences

• Payment count: This model assumes exactly 52 periods per year. Calendar dates can create different intervals or a payment count that is not exactly 52 in a particular year.
• Rate convention: Dividing APR by 52 is a simplifying periodic-rate assumption. A daily accrual convention or a different effective-rate method can change results.
• Rounding: The weekly payment is rounded to cents. A lender may round interest each period, adjust the final payment, or use other contract-specific procedures.
• Extra or missed payments: Additional principal payments, payment holidays, late payments, and rate changes are not modeled. These change the balance path and payoff date.
• Included costs: The calculator does not add origination charges or other costs to principal, or include separate escrow, insurance, or tax payments.

A useful distinction: multiplying a rounded weekly payment by 260 gives the modeled total of scheduled payments, but the lender’s final installment may be slightly different after period-by-period interest rounding. The formula also assumes the payment is sufficient to repay the balance within the stated term.

Frequently Asked Questions

How do I calculate a weekly loan payment?
Convert APR to a weekly periodic rate by dividing the percentage rate by 5,200, set the payment count to years × 52, and use the level-payment formula shown above. Round the result to cents for an estimate.

Is a weekly payment lower than a monthly payment?
A weekly installment is usually smaller in amount because it is one of more frequent payments, but the schedules cannot be compared by installment size alone. Compare total payments, total interest, timing, and the lender’s exact terms.

Does paying weekly save interest?
It may change interest under some loan terms because principal can be credited earlier or more frequently, but the result depends on how payments are posted and calculated. This calculator assumes regular weekly periods and does not model a lender’s specific posting rules.

Is weekly the same as biweekly?
No. Weekly means 52 payments per year; biweekly means 26 payments per year. They have different payment amounts and timing, so use the schedule specified in the loan agreement.

Why does my lender’s payment differ?
Possible causes include daily interest accrual, payment dates, fees included in the financed balance, a different APR convention, period-by-period rounding, or a final adjusted payment. Ask the lender for its amortization schedule and the assumptions used.

This result is an estimate, and the lender’s disclosure gives the exact figures.

Related

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• Weekly vs Monthly Loan Payment Calculator

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Weekly payment | $ | p * (apr / 5200) / (1 - (1 + apr / 5200) ^ -(yrs * 52)) | 2
out int | Total interest | $ | pmt * yrs * 52 - p | 2