30 Year Amortization Schedule Calculator

This 30-year amortization schedule calculator estimates a fixed-rate loan’s monthly payment, total interest, and balance after 30 years of monthly payments. Enter the loan amount and APR to see the payment-by-payment structure behind the estimate; it is for understanding loan arithmetic, not financial advice.

Formula

The level monthly payment is calculated as:

M = round(P × r / (1 − (1 + r)−n), 2)

Here, M is the monthly payment in dollars, P is the starting principal in dollars, r = APR / 1200 is the monthly interest rate as a decimal, and n = years × 12 is the number of monthly payments. APR is entered as a percentage per year. The calculator rounds the scheduled payment to cents before calculating total interest.

Total interest is I = M × n − P, in dollars. The balance after payment k is Bₖ = P(1 + r)ᵏ − M((1 + r)ᵏ − 1) / r, where Bₖ is the remaining principal in dollars and k is the number of payments made. This calculator reports the balance after all scheduled payments; small rounding differences can leave a few cents rather than exactly zero.

Worked Example

Using the calculator’s default values: principal P = $200,000, APR = 6%, and term = 30 years.

• Monthly rate: r = 6 / 1200 = 0.005.
• Number of payments: n = 30 × 12 = 360.
• Payment: M = round(200,000 × 0.005 / (1 − 1.005−360), 2) = $1,199.10.
• Total of scheduled payments: $1,199.10 × 360 = $431,676.00.
• Total interest: $431,676.00 − $200,000 = $231,676.00.
• Balance after 360 payments, using the balance formula and rounded payment: approximately $−0.10; this near-zero residual reflects cent rounding, not a meaningful negative debt.

Assumptions

• The APR and scheduled payment remain fixed throughout the modeled term.
• Payments are made monthly, at the end of each monthly period.
• Interest accrues monthly using APR divided by 12; the model treats APR as the nominal annual rate.
• The estimate excludes fees, taxes, insurance, PMI, escrow, and any payment changes or extra payments.

Reading a 30-Year Schedule

An amortization schedule is a timeline showing how each payment is divided between interest and principal. At the beginning of a level-payment loan, the outstanding balance is larger, so the interest portion is generally larger too. As principal is paid down, less interest accrues in later periods and more of each unchanged payment goes toward principal.

For a 30-year term, the schedule contains 360 monthly periods. The payment result is the principal-and-interest amount under the stated inputs, not necessarily the full amount due on a housing or other loan bill. A lender’s actual payment may include separate charges or use different timing, rounding, or rate terms.

The total-interest result adds the rounded monthly payment over all 360 periods and subtracts the starting principal. It is an estimate based on the entered APR and term; it does not include charges outside the formula. The final-balance formula is useful for checking the balance at a chosen point, but this calculator displays only the balance after the complete term. A value extremely close to zero can occur because the payment is rounded to cents.

When to Use This Calculator

Use the schedule to understand the mechanics of a fixed-rate loan with monthly payments, compare different hypothetical principal, APR, or term inputs, or check how much scheduled interest follows from those assumptions. It is also a starting point for reviewing a lender-provided schedule: compare the inputs and calculation basis rather than assuming the estimate includes every line on a statement.

To explore a different term, replace the 30-year default with the term being modeled. To estimate a balance partway through repayment, use the balance formula with the appropriate number of completed payments; the final-balance output here is specifically for the end of the entered term. Extra principal payments are not modeled, so they should not be treated as if they were included in these totals.

Common Mistakes and Limits

• Enter APR as a percentage, such as 6 for 6%, not as 0.06; the formula divides the percentage by 1,200.
• Use the loan principal rather than a total that includes charges not financed into the loan.
• Do not interpret the monthly result as a complete housing payment; taxes, insurance, escrow, and other costs are outside this calculation.
• Keep in mind that actual statements can differ because of payment dates, fees, rounding conventions, variable rates, or contract-specific terms.
• A term entered in years is converted to 12 monthly periods per year; entering months as years would produce a substantially different result.

The formula models a fixed rate and regular level payments. It does not calculate variable-rate changes, skipped or late payments, prepayments, fees, or a payoff quote. Get the actual APR, payment schedule, and any included costs from the lender rather than substituting general assumptions.

How to Use This List

This page combines the calculator with the key schedule concepts, so start by entering the principal, APR, and term from the loan information you want to examine. Check that APR is expressed as a percent per year and the term as years. Use the payment and interest outputs as estimates, then compare them with the lender’s own disclosure, which may include details this calculation omits.

Frequently Asked Questions

What does a 30-year amortization schedule show?
It lays out how regular monthly payments are allocated between interest and principal and how the balance changes over 360 months.

Does this calculator include property taxes or insurance?
No. It estimates principal and interest only; taxes, insurance, PMI, escrow, and fees are excluded.

Why can the final balance be slightly different from zero?
The scheduled payment is rounded to cents, so repeating it over many periods can leave a small rounding residual.

Can I use it for a variable-rate loan?
Not as a full schedule. The formula assumes one fixed APR for the entire term and does not model future rate changes.

Does an extra payment change the result?
Extra payments are not included. They change the timing of principal reduction and require a schedule that accounts for their amount and dates.

Where should I get the APR and exact payment?
Use the figures supplied for the specific loan by its lender; this page does not provide current rates or lender terms.

Final Thoughts

A 30-year amortization schedule makes the relationship between payment, interest, and remaining principal easier to follow. Treat the outputs as an educational estimate; the lender’s disclosure gives the exact figures.

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in p | Loan amount | $ | 200000 | 1 | 100000000
in apr | Interest rate (APR) | % | 6 | 0.01 | 100
in yrs | Loan term | years | 30 | 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
out bal | Balance after final payment | $ | p * (1 + apr / 1200) ^ (yrs * 12) - pmt * ((1 + apr / 1200) ^ (yrs * 12) - 1) / (apr / 1200) | 2