Quarterly Loan Amortization Schedule Calculator

A quarterly loan amortization schedule shows how each three-month payment is split between interest and principal, and how the balance changes over time. Enter the loan amount, annual APR, and term to calculate the quarterly payment and total interest; the schedule itself can be built by applying the same calculation to each quarter.

Formula

For a fixed-rate loan with equal quarterly payments, the payment is calculated using the standard level-payment amortization formula:

Payment = P × r / [1 − (1 + r)⁻ⁿ]

• P is the original principal, in dollars.
• r is the quarterly interest rate as a decimal. With an annual APR entered as a percentage, r = APR / 400. For example, an 8% APR gives a quarterly rate of 0.02.
• n is the number of quarterly payments: loan term in years × 4.

The displayed payment is rounded to cents. Total interest here is estimated as the rounded payment multiplied by the number of payments, minus the original principal. That convention makes the displayed total consistent with the displayed payment, but a real final payment may be adjusted slightly to clear the remaining balance.

Worked Example

Using the calculator defaults—$20,000 principal, 8% APR, and a five-year term:

1. Quarterly rate: 8 / 400 = 0.02, or 2%.
2. Number of payments: 5 × 4 = 20.
3. Payment: $20,000 × 0.02 / [1 − (1.02)⁻²⁰] = $1,223.80, rounded to the nearest cent.
4. Total of scheduled payments: $1,223.80 × 20 = $24,476.00.
5. Estimated total interest: $24,476.00 − $20,000 = $4,476.00.

These figures assume all payments are made as scheduled. The payment formula produces the level payment; to see the amortization schedule, calculate the interest and principal portions for each quarter.

How a Quarterly Schedule Works

At the start of each quarter, interest accrues on the outstanding balance. The scheduled payment first covers that period’s interest; whatever remains reduces principal. As principal falls, the interest portion usually declines and the principal portion rises, even though the scheduled payment stays level.

For a standard schedule using the quarterly rate r:

• Quarterly interest = opening balance × r.
• Principal repaid = payment − quarterly interest.
• Closing balance = opening balance − principal repaid.

The closing balance for one quarter becomes the opening balance for the next. For the example, first-quarter interest is $20,000 × 0.02 = $400. The $1,223.80 payment therefore repays $823.80 of principal, leaving an estimated balance of $19,176.20. In the second quarter, interest is calculated on that lower balance: $19,176.20 × 0.02 = $383.52. The payment then repays about $840.28 of principal.

When Quarterly Payments Apply

Quarterly amortization is relevant when a loan agreement sets payments every three months. The interval matters: a quarterly payment is not simply a monthly payment multiplied by three. The interest period, number of scheduled payments, and payment timing all affect the calculation. Confirm whether the contract uses a quarterly rate derived from APR, a stated periodic rate, or a different accrual convention.

To construct a full schedule, create one row per payment date with the payment number, opening balance, interest, principal, payment, and closing balance. Continue until the balance reaches zero. A spreadsheet can fill down the calculations, but the contractual payment dates and rounding rules should govern if they differ from this estimate.

How to Read the Result

The quarterly payment is the modeled amount due at each regular payment period, not a monthly amount. The total-interest result estimates interest over the full term under the entered assumptions. It does not show the balance at an arbitrary date or include charges outside the principal-and-interest calculation.

For a balance after a particular number of payments, use the recurrence in the schedule: each period’s closing balance follows from its opening balance, interest, and payment. If the requested date falls between payment dates, the balance may require a separate daily-accrual calculation based on the lender’s method.

Common Mistakes and Limits

• Confusing APR with a quarterly rate: The calculator converts annual percentage APR to a quarterly rate by dividing by 400. Do not enter 8 as though it were a quarterly percentage.
• Using the wrong payment count: A five-year quarterly schedule has 20 payments, not 60. The term must be converted to years × 4.
• Assuming every loan uses this convention: Some contracts accrue interest daily or use other payment and compounding rules. Their schedules can differ from this periodic model.
• Ignoring cent rounding: Rounding each period’s interest and principal can create a small difference in the last payment. A lender may adjust that payment according to its contract and servicing method.
• Adding fees or extra payments implicitly: Neither is included here. An extra principal payment changes later balances and interest; fees may change the amount financed or total borrowing cost.

The formula assumes a positive APR and a term expressed in years. It is an estimate of level-payment principal-and-interest arithmetic, not a substitute for the lender’s disclosed payment schedule.

Assumptions

• Interest rate is fixed for the full modeled term.
• Payments are equal and made at the end of each three-month period.
• Interest is modeled quarterly at APR divided by four, equivalent to APR / 400 as a decimal rate.
• Fees, taxes, insurance, mortgage insurance, escrow, and other charges are not included.

Frequently Asked Questions

How do you calculate a quarterly loan payment?
Convert APR to a quarterly decimal rate by dividing the percentage by 400, set the payment count to years × 4, and apply the level-payment formula shown above.

Is a quarterly payment three times the monthly payment?
No. The payment interval changes how interest accrues and how many payments are made. Calculate the loan using the actual quarterly rate and payment count rather than multiplying a monthly figure by three.

How much of each quarterly payment goes to principal?
Subtract that quarter’s interest from the payment. Interest is the opening balance multiplied by the quarterly rate; the remainder reduces principal.

Why might a lender’s schedule differ from this estimate?
The lender may use daily interest accrual, different compounding or payment timing, fees, a variable rate, or specific rounding and final-payment procedures. Check the loan disclosure for the terms used.

Can I use this calculator for a variable-rate loan?
Only for a period in which the entered APR is applicable. If the rate changes, the payment or remaining schedule may be recalculated under the contract, so a single fixed-rate calculation cannot represent the entire loan.

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

Related

• 30 Year Amortization Schedule Calculator
• 20 Year Amortization Schedule Calculator and Guide
• 15 Year Amortization Schedule 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 | Quarterly payment | $ | round(p * (apr / 400) / (1 - (1 + apr / 400) ^ -(yrs * 4)), 2) | 2
out int | Total interest | $ | pmt * yrs * 4 - p | 2