360 Day Loan Payment Calculator and Formula

This calculator estimates a level monthly payment for a loan using a 360-day-year convention, along with total interest over the stated term. Enter the principal, annual APR, and term in years to see the monthly payment and interest estimate.

Formula

The calculator applies the standard fixed-payment amortization formula with monthly periods. Although the page refers to a 360-day convention, this estimate treats each month as one-twelfth of a year and uses a periodic rate of APR divided by 12; it does not calculate daily interest using actual dates.

Monthly payment: M = round(P × r ÷ [1 − (1 + r)⁻ⁿ], 2), where r = APR ÷ 1200 and n = 12 × Y.

Total interest: I = M × n − P.

P is the starting loan principal in dollars, APR is the annual percentage rate entered as a percent, r is the monthly rate as a decimal, Y is the term in years, n is the number of monthly payments, M is the payment in dollars rounded to cents, and I is total interest in dollars based on that rounded payment. The results assume the scheduled payment is made for every month of the entered term.

Worked Example

Using the calculator defaults: principal P = $20,000, APR = 8%, and term Y = 5 years.

1. Convert the APR to a monthly decimal rate: r = 8 ÷ 1200 = 0.0066667.
2. Find the number of monthly payments: n = 5 × 12 = 60.
3. Substitute into the payment formula: M = round(20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰], 2) = $405.53.
4. Calculate total interest using the rounded payment: I = $405.53 × 60 − $20,000 = $4,331.80.

Assumptions

• The APR and payment amount stay fixed throughout the term.
• Payments are made monthly, at the end of each period, with the first payment one month after borrowing.
• Interest compounds monthly at APR ÷ 12; a daily 30/360 or actual/360 accrual schedule is not modelled.
• Fees, taxes, insurance, PMI, escrow, late charges, and any balloon payment are not included.

When to Use This Calculator

Use this estimate when you want to understand the basic scheduled payment and interest for a fixed-rate loan with monthly installments. It can help you check a hypothetical amount, rate, and term, or compare the arithmetic of different input scenarios without treating the result as a lending quote. Enter the amount borrowed rather than the total purchase price if a down payment or other funds reduce what is financed.

For a 360-day loan, the phrase can refer to a day-count convention used to accrue interest between dates, often by treating the year as twelve 30-day months. The exact calculation can depend on the contract and payment dates. This calculator does not have calendar dates or a day-count input, so it cannot reproduce a lender’s daily accrual, irregular first period, or payoff figure. Check the loan documents for the precise convention and use the lender’s stated payment schedule when exact figures matter.

Reading the Results

The monthly payment is the scheduled principal-and-interest amount under the formula, not a complete estimate of all monthly costs. Total interest is the sum of the rounded monthly payments across the full term minus the original principal. A longer term generally produces more scheduled payments, while changing the APR changes the monthly interest rate used by the formula. These are mathematical effects of the entered assumptions, not a forecast of an offer or of a borrower’s circumstances.

Common Input Mistakes

• Enter APR as a percentage such as 8, not as 0.08; the calculator divides the percentage by 1200 to get a monthly decimal rate.
• Enter the term in years, not months. For a five-year term, type 5.
• Use the amount financed as principal. Adding a fee to principal changes both the payment and total interest.
• Do not interpret the result as daily 360-day accrual. A daily convention needs dates, a balance path, and the contract’s interest method.
• Expect small differences from a statement or quote when payment rounding, first-payment timing, fees, or an irregular period differs.

Limits of the Estimate

This is an amortization estimate, not financial advice or a loan offer. It does not determine approval, include lender-specific charges, or account for changes in a variable rate. The real APR, fees, payment dates, and any day-count details must come from the lender’s documents; the calculation cannot establish those inputs. Results are rounded to cents for the payment, and total interest uses that rounded payment, so the final scheduled payment could differ if a lender adjusts it to clear a remaining balance. The result is an estimate, and the lender’s disclosure gives the exact figures.

How to Use This List

This page is a single-purpose calculator rather than a directory of loan products. Start with the amount actually borrowed, then enter the APR and term from a written quote or use clearly labelled hypothetical inputs. If your agreement specifies daily 30/360 accrual, ask for its payment schedule instead of assuming this monthly model matches it. Change one input at a time when examining how assumptions affect the estimate, and keep the lender’s disclosed figures separate from calculator results.

Frequently Asked Questions

Does this calculator use a true 360-day daily-interest method?

No. It uses monthly amortization with APR divided by 12. It does not calculate interest day by day or use calendar dates.

What does 360-day interest mean?

It generally describes a day-count method that treats a year as 360 days, often with twelve 30-day months. Contract details determine how that convention is applied.

Why might my payment differ from the calculator?

Payment timing, daily accrual, fees added to the balance, rounding, or a nonstandard first period can change the amount shown by a lender.

Does total interest include fees or insurance?

No. It is calculated from the rounded principal-and-interest payment and the original principal only.

Can I use it for a variable-rate loan?

Only as a snapshot using one assumed APR for the whole term. It does not model future rate changes or payment recalculation.

Final Thoughts

Use the result as a transparent monthly-payment estimate, and verify the loan’s day-count convention, schedule, and charges against its disclosure before relying on exact figures.

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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 | Monthly payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2