🏠 Mortgage Calculator
By ToolNimba Finance Team · Reviewed by ToolNimba Editorial Review, personal finance content · Updated 2026-06-19
This calculator gives an estimate only. Your actual mortgage cost depends on your lender fees, points, private mortgage insurance, escrow for taxes and insurance, the exact compounding convention, and whether the rate is fixed or adjustable. The result is not financial advice, confirm the final figures with your lender and speak to a qualified mortgage professional before borrowing.
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This mortgage calculator works out the monthly payment on a home loan and shows what the loan really costs once interest is added in. Enter the home price, your down payment, the annual interest rate, and the loan term in years. You will instantly see the monthly principal and interest payment, the loan amount, the total interest paid, and the full amount repaid over the term. You can also add annual property tax and home insurance to estimate the complete monthly housing cost.
What is the Mortgage Calculator?
A mortgage is a long-term loan used to buy property, repaid in equal monthly installments over a fixed term, most commonly 15 or 30 years. The amount you actually borrow is the loan principal, which equals the home price minus your down payment. A larger down payment means a smaller loan, a lower monthly payment, and far less interest over the life of the mortgage. It can also help you avoid private mortgage insurance, which lenders often require when the down payment is under 20 percent.
The monthly principal and interest payment is found with the standard amortizing loan formula M = P times r times (1 + r) to the power n, divided by ((1 + r) to the power n minus 1). Here P is the loan amount, r is the monthly interest rate (the annual rate divided by 12 and by 100), and n is the number of monthly payments (years times 12). The payment is level for the whole term, so the lender solves for the exact figure that clears the balance to zero by the final month.
Inside each payment, the split between interest and principal shifts over time. In the early years most of the payment is interest because the outstanding balance is large, so only a small slice reduces what you owe. As the balance falls, the interest portion shrinks and more of each fixed payment goes to principal. This front-loading is why extra payments made early in a mortgage save much more interest than the same payments made near the end. Your true monthly housing cost is usually higher than principal and interest alone, because property tax, home insurance, and any mortgage insurance are typically collected on top, often through an escrow account.
When to use it
- Estimating the monthly payment on a home before you make an offer or get pre-approved.
- Comparing a 15-year and a 30-year term to weigh a higher monthly payment against far lower total interest.
- Seeing how a bigger down payment lowers both the monthly payment and the lifetime interest cost.
- Budgeting the full monthly housing cost by adding property tax and home insurance to principal and interest.
How to use the Mortgage Calculator
- Enter the home price you are planning to pay.
- Enter your down payment, the loan amount is the price minus this figure.
- Enter the annual interest rate your lender is quoting.
- Enter the loan term in years, usually 15 or 30.
- Optionally add annual property tax and home insurance to see the full monthly cost.
- Read off the monthly payment, total interest, and total paid over the term.
Formula & method
Worked examples
A $300,000 home with no down payment, at 6% annual interest over 30 years (360 months).
- Loan amount P = 300,000 − 0 = 300,000
- Monthly rate r = 6 ÷ 12 ÷ 100 = 0.005
- (1 + r)ⁿ = 1.005^360 = 6.022575
- M = 300,000 × 0.005 × 6.022575 ÷ (6.022575 − 1)
- M = 9,033.86 ÷ 5.022575 = 1,798.65
- Total paid = 1,798.65 × 360 = 647,514.57
- Total interest = 647,514.57 − 300,000 = 347,514.57
Result: Monthly P+I ≈ $1,798.65 · Total interest ≈ $347,514.57 · Total paid ≈ $647,514.57
A $400,000 home with an $80,000 down payment, at 7% annual interest over 30 years.
- Loan amount P = 400,000 − 80,000 = 320,000
- Monthly rate r = 7 ÷ 12 ÷ 100 = 0.0058333
- (1 + r)ⁿ = 1.0058333^360 = 8.116497
- M = 320,000 × 0.0058333 × 8.116497 ÷ (8.116497 − 1)
- M = 15,150.80 ÷ 7.116497 = 2,128.97
- Total paid = 2,128.97 × 360 = 766,428.47
- Total interest = 766,428.47 − 320,000 = 446,428.47
Result: Monthly P+I ≈ $2,128.97 · Total interest ≈ $446,428.47 · Total paid ≈ $766,428.47
Monthly principal and interest on a $300,000 loan by rate and term
| Rate | 30-year monthly | 30-year total interest | 15-year monthly |
|---|---|---|---|
| 5% | $1,610.46 | $279,767.35 | $2,372.38 |
| 6% | $1,798.65 | $347,514.57 | $2,531.57 |
| 7% | $1,995.91 | $418,526.69 | $2,696.48 |
| 8% | $2,201.29 | $492,465.74 | $2,866.96 |
How the down payment changes a loan on a $400,000 home at 6% over 30 years
| Down payment | Loan amount | Monthly P+I | Total interest |
|---|---|---|---|
| $0 (0%) | $400,000 | $2,398.20 | $463,352.76 |
| $40,000 (10%) | $360,000 | $2,158.38 | $417,017.48 |
| $80,000 (20%) | $320,000 | $1,918.56 | $370,682.20 |
| $120,000 (30%) | $280,000 | $1,678.74 | $324,346.93 |
Common mistakes to avoid
- Budgeting only for principal and interest. The monthly P+I is not your full housing cost. Property tax, home insurance, and private mortgage insurance are usually collected on top, often through escrow, and can add hundreds of dollars a month. Add tax and insurance here for a more realistic figure.
- Choosing a 30-year term purely for the lower payment. A 30-year loan has a smaller monthly payment than a 15-year loan, but you pay interest for twice as long, so the total interest is far higher. On a $300,000 loan at 6%, the 30-year option costs more than double the interest of the 15-year option.
- Underestimating the value of a bigger down payment. Putting more down shrinks the loan, lowers the monthly payment, and cuts lifetime interest. Reaching 20 percent down also commonly removes the requirement for private mortgage insurance, saving more each month.
- Assuming an adjustable rate stays fixed. This calculator uses a single fixed rate. If you have an adjustable-rate mortgage, the payment can rise or fall when the rate resets, so treat the result as a snapshot at today rate only.
Glossary
- Principal
- The loan amount you actually borrow, equal to the home price minus your down payment.
- Down payment
- The cash you pay upfront toward the home price, reducing the amount you need to finance.
- Interest rate
- The annual cost of borrowing, expressed as a percentage. Divided by 12 it gives the monthly rate used in the formula.
- Term
- The length of the mortgage in years, most often 15 or 30, which sets the number of monthly payments.
- Amortization
- The schedule that splits each level payment into interest and principal and brings the balance down to zero.
- Escrow
- An account the lender uses to collect and pay your property tax and insurance alongside the loan payment.
- PMI
- Private mortgage insurance, a charge lenders often require when the down payment is below 20 percent of the price.
- Loan-to-value (LTV)
- The loan amount as a percentage of the home value. A lower LTV usually means better terms and no PMI.
Frequently asked questions
How is a monthly mortgage payment calculated?
The principal and interest payment uses the amortizing formula M = P·r·(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the loan amount, r is the monthly rate (annual rate ÷ 12 ÷ 100), and n is the number of months (years × 12). The calculator applies it automatically and can add monthly property tax and insurance on top.
What is the monthly payment on a $300,000 mortgage at 6% over 30 years?
The principal and interest payment is about $1,798.65 per month. Over the full 30 years you would pay roughly $347,514.57 in interest, for a total of about $647,514.57. Property tax and insurance, if applicable, are extra.
Should I choose a 15-year or 30-year mortgage?
A 15-year loan has higher monthly payments but a lower rate and far less total interest, so you build equity faster and pay less overall. A 30-year loan lowers the monthly payment, which helps cash flow, but you pay interest much longer. The right choice depends on what payment fits your budget comfortably.
Does my down payment affect the monthly payment?
Yes. The loan amount is the price minus the down payment, so a larger down payment means a smaller loan, a lower monthly payment, and less interest over the term. Reaching 20 percent down also commonly removes private mortgage insurance.
Does this calculator include property tax and insurance?
The core result is the principal and interest payment. You can enter annual property tax and home insurance in the optional fields, and the calculator adds the monthly share to show your fuller housing cost. It does not include HOA dues or maintenance.
Can paying extra reduce the total interest?
Yes. Because interest is charged on the outstanding balance, any extra paid toward principal reduces that balance and the interest charged from then on. Extra payments early in the loan save the most, since that is when the balance is largest. Check whether your lender allows penalty-free prepayment.
Sources
- How much can I borrow and what will it cost? , U.S. Consumer Financial Protection Bureau
- Mortgage , Investopedia