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Simple Calculators

Amortization Calculator

Monthly payment and a full month-by-month amortization schedule for any loan

Loan Details

Annual rate, not the APR

Optional; added to principal every month

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Quick summary

A fixed-rate loan's monthly payment is M = P × r ÷ (1 − (1 + r)^−n), where r is the monthly rate and n the number of payments. A $250,000 loan at 6.5% for 30 years costs $1,580.17 a month. Over 360 payments that is $568,861.58 in total, of which $318,861.58 is interest. Early payments are mostly interest; each one shifts a little more toward principal.

Reviewed by Simple Calculators TeamLast reviewed

For planning only — not financial or tax advice. Results are estimates based on your inputs and the stated assumptions. Confirm important decisions with a qualified professional.

How to use this calculator

  1. Enter the Loan Amount ($) you are borrowing or still owe.
  2. Enter the Interest Rate (%) as the annual rate on the loan.
  3. Enter the Loan Term (years), such as 15 or 30.
  4. Optionally add an Extra Monthly Payment ($) to see how much sooner the loan ends.
  5. Read the monthly payment, total interest, and total paid, then switch the schedule between Monthly and Yearly views.

Amortization Formulas

Monthly Payment

M=P×r1−(1+r)−nM = \frac{P \times r}{1 - (1 + r)^{-n}}
M
Monthly principal and interest payment
P
Loan amount
r
Monthly rate: the annual rate ÷ 100 ÷ 12
n
Number of monthly payments: years × 12 (at a 0% rate, M = P ÷ n)

Worked example

$250,000 at 6.5% for 30 years

Given
P = $250,000
r = 0.065 ÷ 12 ≈ 0.0054167
n = 360
Calculation
M=250000×0.00541671−(1.0054167)−360M = \frac{250000 \times 0.0054167}{1 - (1.0054167)^{-360}}
Result
M ≈ $1,580.17 per month

Interest and Principal Each Month

Ik=Bk−1×r,Principalk=M−IkI_k = B_{k-1} \times r, \quad \text{Principal}_k = M - I_k
I_k
Interest charged in month k
B_{k-1}
Balance before the month k payment

Worked example

Month 1 of the same loan

Given
B_0 = $250,000
M = $1,580.17
Calculation
I1=250000×0.06512=1354.17,1580.17−1354.17=226.00I_1 = 250000 \times \frac{0.065}{12} = 1354.17, \quad 1580.17 - 1354.17 = 226.00
Result
$1,354.17 interest and $226.00 principal; balance $249,774.00

Total Interest

Total interest=∑k=1nIk≈M×n−P\text{Total interest} = \sum_{k=1}^{n} I_k \approx M \times n - P
M × n
Every scheduled payment added up
P
Loan amount repaid

Worked example

The same loan over its full term

Given
M = $1,580.17
n = 360
Calculation
1580.17×360−250000≈3188611580.17 \times 360 - 250000 \approx 318861
Result
≈ $318,861.58 in interest (the final payment absorbs the rounding)

Frequently asked questions

What is an amortization schedule?

It is a table of every payment on a loan, showing how much goes to interest, how much goes to principal, and the balance left afterwards. The payment stays the same, but because interest is charged on the shrinking balance, the interest share falls and the principal share grows each month.

Why is so much of my early payment interest?

Interest is charged on the balance you still owe, and the balance is largest at the start. In the first month of a $250,000 loan at 6.5%, interest is $250,000 × 0.065 ÷ 12 = $1,354.17, so only $226.00 of the $1,580.17 payment reduces the balance.

How do extra payments change the schedule?

Extra money paid toward principal lowers the balance immediately, so every later month charges less interest and the loan ends sooner. Enter an amount in Extra Monthly Payment to see the shorter payoff time and the interest saved. Lenders handle extra payments differently, so check your loan terms and confirm extra amounts are applied to principal.

Does the monthly payment include taxes and insurance?

No. This calculator shows principal and interest only. A mortgage payment often also includes property tax, homeowners insurance, and sometimes mortgage insurance collected through escrow, so your total monthly bill can be higher.

Why might my lender's numbers differ slightly?

Lenders may round differently, calculate interest daily rather than monthly, or adjust the final payment. Results here are estimates for a fixed-rate loan with interest charged monthly and rounded to the cent; your loan documents are the authoritative source.

Key terms

Amortization
Paying off a loan with regular fixed payments that cover the interest due and gradually repay the principal.
Principal
The amount borrowed, or the part of it still owed.
Interest
The cost of borrowing, charged each month on the remaining balance.
Loan Term
The length of time over which the loan is scheduled to be repaid, such as 15 or 30 years.

Methodology, sources & limitations

This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.

For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.