Mortgage Calculator

Free mortgage calculator: enter the loan amount, interest rate and term to get your monthly payment, total interest and a full amortization schedule by year and month. Compare fixed monthly payments with equal principal side by side, add an interest-only period or a rate change. No sign-up, nothing uploaded.

  • Amortization schedule by year & month
  • Fixed payment vs equal principal
  • Interest-only period
  • Two-step interest rate
You pay only interest during this period. Enter 0 if there is none.
Advanced: two-step rate

When ticked, the rate above applies first, then the second rate applies.

🔒 Everything is calculated in your browser. No data is sent to any server.

When to use it

  • How much house can I afford: enter the amount you plan to borrow and the term to see the monthly payment before you start shopping.
  • Amortization schedule: see how much of each year's payments goes to interest and how fast the balance drops.
  • Interest-only mortgage: compare the payment during the interest-only period with the payment once principal repayment starts.
  • Rate reset planning: use a two-step rate to see how the payment changes when an introductory rate ends.

How to use

  1. Enter the loan amount, annual interest rate and loan term in years.
  2. Choose a repayment method and, if your loan starts with an interest-only period, enter its length in years (otherwise 0).
  3. If the rate changes partway through, open “Advanced: two-step rate”, tick it, and enter the years at the first rate and the second rate.
  4. The monthly payment, total interest, method comparison and yearly schedule update as you type; click a year to expand its months.
  5. To go over the numbers with family, press “Copy share link”: anyone who opens it sees the same inputs.

Worked example

With the default values: a 300,000 loan at 6% for 30 years with fixed monthly payments. The payment is 1,799 a month, total interest over 30 years is 347,515 and the total paid is 647,515. Of the roughly 21,584 paid in year 1, 17,900 is interest and only 3,684 goes to principal; after 10 years the balance is still 251,057.

Switching to equal principal under the same terms: the first payment is the highest at 2,333, then it falls every month to 837 at the end. Total interest is 270,750, which is 76,765 less than fixed payments, but early payments are more than 500 higher.

Shortening the term to 15 years at the same 6% (fixed payments) raises the payment to 2,532 but cuts total interest to 155,683. All rates here are assumptions for illustration.

Reading the results

  • “Payment schedule” splits the loan into stages: interest-only months, and a new payment whenever the rate changes. Each stage shows the payment numbers, the rate and the amount. For equal principal it shows “first … falling to …”, and the first month is the most expensive one.
  • “Compare repayment methods” runs both methods with the same inputs. Equal principal pays down more principal early, so the balance falls faster and total interest is lower. Fixed payments keep every month the same and are easier on the budget at first, but cost more interest overall. At a 0% rate both cost the same.
  • In the chart, the bars are the principal and interest paid each year and the line is the balance at year end. With fixed payments, interest dominates the early years and the principal share grows over time.
  • Click a year in the schedule to expand its 12 monthly payments. Amounts are rounded to whole numbers for display only, so a column may be off by 1 from the total; lenders usually round each payment to the cent, so their numbers can differ slightly.

How it works

  • Monthly rate r = annual rate ÷ 12, and each month's interest = opening balance × r. During an interest-only period you pay only the interest and the balance stays the same.
  • Fixed monthly payment: payment = principal × r × (1 + r)^n ÷ [(1 + r)^n − 1], where n is the number of repayment months; the principal part = payment − that month's interest. At a 0% rate the payment is principal ÷ n.
  • Equal principal: each month repays loan amount ÷ number of repayment months plus interest on the remaining balance, so payments fall every month. With one rate and no interest-only period, total interest = principal × r × (n + 1) ÷ 2.
  • Two-step rate: when the rate changes, fixed payments are recalculated from the remaining balance and remaining months; with equal principal the principal part stays the same and only the interest changes. The last payment clears the remaining balance, so principal repaid always equals the loan amount.

Limitations

  • The rate is your assumption. Real rates depend on your lender, and adjustable rates follow their own index, margin and caps, which are not modeled. Use the results for planning; your lender's figures are what you will actually pay.
  • Property taxes, homeowners insurance, mortgage insurance, HOA dues and closing costs are not included, so your actual monthly housing cost will be higher.
  • Supports up to two rate steps; extra payments, refinancing and biweekly payments are not supported.
  • Rates must be 0–30%, the term 1–50 whole years, and the interest-only period a whole number of years shorter than the term.

FAQ

Which is better: fixed monthly payments or equal principal?

Equal principal costs less interest overall but has much higher payments at the start. Fixed payments stay the same every month, which makes budgeting easier. The comparison table shows the exact difference for your inputs.

What should I enter as the loan amount?

The amount you borrow, usually the home price minus your down payment. Enter the full amount; the calculator does not assume any currency.

Will my lender’s numbers match exactly?

The formula is the standard amortization formula, but lenders round each payment to the cent and may calculate interest daily, so small differences are normal. Your loan documents show the exact amounts.

What is an interest-only period?

For the first years you pay only interest and the balance does not go down. After it ends, the principal has to be repaid over fewer months, so the payment jumps and total interest is higher.

What is the monthly payment on a 300,000 mortgage at 6% for 30 years?

About 1,799 a month with fixed payments, and about 347,515 of interest over the life of the loan. At 6.25% it would be about 1,847, roughly 49 more per month.

Can I calculate extra payments or paying off early?

Not yet. As a rough estimate, enter the balance left after the extra payment and the remaining years as a new loan to see the new payment and interest.

How do I model an introductory rate that resets later?

Open “Advanced: two-step rate”, tick it, keep the intro rate in the rate field, then enter how many years it lasts and the rate afterwards. Fixed payments are recalculated from the remaining balance when the rate changes.

References

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