30-Year Loan Payment Comparison Calculator

This 30-year loan calculator estimates the monthly principal-and-interest payment and total interest for a fixed-rate loan using the amount borrowed and annual APR you enter. Enter each loan’s amount and APR separately to compare its estimated cost; the results do not include taxes, insurance, fees, or other loan terms.

Formula

This calculator uses the standard fixed-payment amortization formula. It estimates the monthly payment by dividing the loan amount multiplied by the monthly interest rate by one minus the discount factor for all scheduled payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount borrowed, in dollars.
• r is the monthly interest rate as a decimal: annual APR ÷ 100 ÷ 12.
• n is the number of monthly payments: loan term in years × 12.
• Payment is the level monthly principal-and-interest amount, in dollars.

The calculator rounds the monthly payment to cents. Total interest is calculated as the rounded monthly payment multiplied by the number of months, minus the original loan amount: Total interest = payment × n − P. Because the payment is rounded, the final scheduled payment on an actual loan may differ slightly.

Worked Example

Using the calculator’s default inputs—$20,000 borrowed, 8% APR, and a five-year term:

1. Convert the annual rate to a monthly decimal: 8 ÷ 1200 = 0.0066667.
2. Find the payment count: 5 × 12 = 60 months.
3. Substitute the values: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰].
4. The monthly principal-and-interest payment is approximately $405.53.
5. Total interest using the rounded payment is $405.53 × 60 − $20,000 = $4,331.80.

Assumptions

• The interest rate stays fixed throughout the stated term.
• Payments are equal monthly installments, made at the end of each monthly period.
• Interest compounds monthly using APR divided by 12.
• The estimate excludes fees, taxes, insurance, PMI, escrow, and any extra payments.

How to Compare 30-Year Loans

For a meaningful comparison, use the same loan amount and term for each quote, and enter each quoted APR as a separate calculation. This isolates how the rate changes the scheduled payment and modeled interest. If one option has a different amount financed or term, the payment comparison reflects those differences too; it does not show the rate’s effect alone.

A 30-year term means 360 scheduled monthly payments. For example, to compare two 30-year offers, enter the same principal and 30 years in each calculation, changing only the APR. A lower APR will produce a lower modeled payment and interest total under these assumptions. Actual offers may also differ in fees, discount points, rate structure, and other costs, so the payment comparison is not a complete measure of total borrowing cost.

The calculator’s term field accepts years, so enter 30 for a 30-year loan. Its example defaults are deliberately just calculation inputs; they are not a statement about available or prevailing rates. Get the actual rate, fees, and payment details from the lender’s written loan information.

What the Payment Does—and Does Not—Include

The result is principal and interest only. A real monthly housing payment may also involve property-related charges, insurance, mortgage insurance, or escrowed costs, depending on the loan and property. Those expenses are not calculated here, and they can change over time. Ask the lender for a breakdown of the full payment and which costs are included.

APR is an annualized rate used here as the interest-rate input; this simple formula treats the entered APR as the nominal yearly rate divided into monthly periods. It does not separately model upfront charges or convert them into an effective borrowing cost. If a lender provides both an interest rate and an APR, confirm which figure corresponds to the calculator’s input and ask how fees are reflected in its disclosures.

Reading Results and Common Limits

• Payment: the estimated recurring monthly principal-and-interest amount, rounded to cents.
• Total interest: the modeled interest over all scheduled payments, using that rounded payment.
• Principal: the amount borrowed; it is not itself a fee or interest cost.

Early in a fully amortizing loan, a larger share of each payment generally goes to interest; later, more goes to principal. The calculator does not show an amortization schedule or remaining balance. It also assumes the stated payment is made on time every month and that the rate does not change. Adjustable rates, interest-only periods, balloon payments, payment pauses, late charges, and extra principal payments require different calculations.

Do not treat total interest as the full cost of a loan: it leaves out charges that are not inputs. Nor does a smaller monthly payment automatically mean a lower overall cost. A longer repayment period can reduce the scheduled payment while increasing the number of months interest accrues. For a like-for-like comparison, keep the amount and term constant, then separately review fees and other terms.

Frequently Asked Questions

How many payments are in a 30-year loan?
A standard monthly schedule over 30 years has 360 payments. The actual final payment can differ because of rounding, payment timing, or changes not represented by this fixed-rate estimate.

Does a 30-year loan always have a lower monthly payment?
For the same principal and rate, spreading repayment across more months generally lowers the scheduled principal-and-interest payment. It also usually means more time for interest to accrue; this calculator can compare terms by changing the years input.

Is APR the same as the interest rate?
Not necessarily. The terms can represent different measures, especially when fees are involved. This calculator uses the APR you enter as its annual rate divided by 12 and does not independently model fees. Confirm the relevant quoted figure with the lender.

Why is my lender’s payment different?
The quoted figure may use a different principal, rate, payment date, rounding method, or loan structure. It may also include costs excluded here, such as taxes or insurance. Compare the assumptions and request an itemized payment estimate.

Can I compare loans with different amounts or terms?
Yes, but the results then reflect differences in amount and term as well as APR. To isolate the rate effect, hold the amount and term constant and change only the APR.

This result is an estimate, and the lender’s disclosure gives the 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 | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2