Calculator Suite

Loan Calculator

Calculate monthly payments, total interest, and amortization schedules

Loan Details
Enter your loan information to calculate payments and total costs

The total amount you want to borrow

The yearly interest rate for your loan

How long you'll take to repay the loan

Additional amount you plan to pay each month

When your first payment will be due

Common Loan Terms

15 years20 years25 years30 years

Common Interest Rates

3.5%4.0%4.5%5.0%5.5%6.0%
How this calculator works
Method, formula, examples, assumptions, and review notes for this calculator.

How this calculator works

  • The calculator treats the loan as a fixed-rate amortizing loan with equal scheduled monthly payments.
  • Each payment first covers the interest accrued for that month; the remainder reduces principal.
  • Optional extra monthly payments are applied to principal after the scheduled payment and can shorten the payoff date.

Formula

Fixed-rate amortizing loan payment

M=Pr(1+r)n(1+r)n−1M = P \frac{r(1+r)^n}{(1+r)^n - 1}

Plain text formula: Monthly payment = principal x monthly rate x (1 + monthly rate)^number of months / ((1 + monthly rate)^number of months - 1).

M = monthly principal-and-interest payment
P = loan principal
r = monthly interest rate, annual rate divided by 12
n = total number of monthly payments

Worked examples

Thirty-year fixed loan

Inputs

  • Principal: $300,000
  • Annual interest rate: 6.5%
  • Term: 360 months
  • Extra payment: $0

Calculation

  • Monthly rate = 0.065 / 12 = 0.0054167.
  • Scheduled payment is about $1,896.20 for principal and interest.
  • Total paid is about $682,633, so total interest is about $382,633.

A lower monthly payment from a long term can still create a high total interest cost because interest accrues for many years.

Same loan with extra principal

Inputs

  • Principal: $300,000
  • Annual interest rate: 6.5%
  • Term: 360 months
  • Extra payment: $100 per month

Calculation

  • The scheduled payment is unchanged, but $100 is added to principal each month.
  • The balance reaches zero earlier because less interest accrues on later payments.

Extra principal payments can reduce both payoff time and lifetime interest, but the best choice depends on cash flow and other obligations.

Curated video guide
Selected YouTube lessons that add context after the calculator, formulas, examples, assumptions, and limitations.

Amortization schedules and time to pay off

Source: Khan Academy on YouTube

Why this video: Selected because it explains amortization schedules from an educational source without promoting a lender, product, or refinancing offer.

What it adds: It reinforces how each payment is split between interest and principal, which complements the payment formula and amortization table.

Use with this calculator: Use the calculator first, then compare the monthly payment and payoff months with the video's schedule-based explanation.

Limits: The video is conceptual education and does not include taxes, insurance, fees, credit terms, or personal financial advice.

How to interpret your result

  • Compare the monthly payment against your budget, then compare total interest against the amount borrowed.
  • When comparing loan offers, consider APR, fees, term length, and total interest instead of monthly payment alone.

Assumptions

  • Interest rate stays fixed for the entire term.
  • Payments are made monthly and on time.
  • Extra payments, if entered, are made consistently every month.

Limitations

  • The estimate does not include taxes, insurance, PMI, origination fees, late fees, or closing costs.
  • Adjustable-rate loans, balloon payments, and irregular payment schedules are not modeled.
  • Actual lender amortization can differ because of rounding and payment timing rules.

Common mistakes

  • Comparing only monthly payment while ignoring total interest.
  • Entering APR and interest rate interchangeably when fees are included in APR.
  • Using a mortgage estimate as a full housing-cost estimate without adding taxes and insurance.

Sources

Consumer Financial Protection Bureau: compare loan offersConsumer Financial Protection Bureau: compare auto loan offers

Disclaimer

Last updated and reviewed by

Updated 2026-06-06Calculator Suite editorial review