How this calculator works
This calculator estimates the fixed monthly payment for a loan paid down in equal installments over a set term. You enter the loan or purchase amount (principal), annual interest rate, and repayment length in years.
The payment uses standard fixed-rate amortization math. Each month, interest is charged on the remaining balance at the periodic rate (annual rate divided by 12). The fixed payment covers that interest plus principal that reduces the balance. Early payments apply more to interest because the balance is larger; later payments apply more to principal as the balance shrinks.
Outputs include the monthly payment, total interest over the life of the loan, total principal plus interest cost, and a month-by-month amortization schedule. The schedule shows payment, principal portion, interest portion, and remaining balance for each period.
The calculator uses the note rate you enter—not APR. It assumes equal monthly payments, no prepayments, and no fees rolled into the loan unless you include them in the principal amount. It does not add property taxes, insurance, mortgage insurance, or other escrow items common on home loans.
Use the rate from your pre-approval letter or loan agreement for the most accurate principal-and-interest estimate. Compare multiple term and rate combinations by changing inputs and reviewing how total interest responds.
What affects the result
Three inputs drive the payment and total cost, and small changes in any of them compound over a long term.
- Loan or purchase amount is the principal borrowed. A higher amount raises the monthly payment because more money must be repaid. On mortgages, this is the loan size after down payment—not the home's full purchase price unless you enter purchase price minus down payment.
- Interest rate is the annual borrowing cost expressed as a percentage. A higher rate increases both the monthly payment and total interest. Even a 0.25 or 0.5 percentage point difference matters over a 30-year mortgage.
- Loan term is the repayment length in years. A longer term spreads the same principal over more payments, which usually lowers the monthly payment but increases total interest because the balance accrues interest for more months. A shorter term does the opposite.
The amortization schedule makes the tradeoff visible. You can see how much interest accumulates in the first year versus the last, and when the remaining balance crosses thresholds that matter for refinancing or PMI removal.
Real-world examples
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Standard 30-year mortgage. You borrow $350,000 at 6.5% for 30 years. The estimated monthly principal-and-interest payment is about $2,212, with total interest near $446,000 over 360 payments. That total interest figure is why rate shopping and extra principal payments matter on long loans.
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15-year versus 30-year comparison. The same $350,000 at 6.5% on a 15-year term produces a payment near $3,049—roughly $837 more per month than the 30-year option—but total interest drops to about $199,000. The shorter term saves interest but requires higher monthly cash flow.
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Personal loan payoff. You take a $20,000 personal loan at 11% for 5 years. The payment is about $435 per month with roughly $6,100 in total interest. Shorter terms or lower rates reduce that interest cost; this calculator helps compare offers before you sign.
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Rate shopping on a refinance-sized balance. On $280,000 over 30 years, 6.0% yields a payment near $1,679 while 6.75% yields about $1,817—a $138 monthly difference that adds up to tens of thousands in total interest over the full term.
Common mistakes
- Confusing note rate with APR. APR reflects some fees and costs; this calculator uses the rate you enter directly. Compare loan offers carefully about which number you are modeling.
- Forgetting that mortgage PITI is more than principal and interest. Property taxes, homeowners insurance, and PMI can add hundreds to the monthly housing bill even when P&I stays fixed.
- Assuming a lower payment always saves money. Extending the term lowers the payment but often raises lifetime interest. Always check total interest alongside the monthly number.
- Entering purchase price instead of loan amount. If you put $80,000 down on a $400,000 home, enter $320,000 as principal unless you intentionally model zero down payment.
- Ignoring that actual schedules may differ slightly. Lenders round differently, use exact day counts in some programs, or include fees that change effective cost. Treat output as a close planning estimate.
- Expecting the calculator to model extra payments. Extra principal payments shorten payoff and reduce interest but are not built in here. The schedule shows the baseline fixed payment only.
When to use this calculator
Use this calculator when you know the loan amount, rate, and term and need a quick principal-and-interest payment. It fits fixed-rate mortgages, personal loans, and many installment loans that amortize on a schedule like this one.
Run it when comparing 15-year versus 30-year mortgages, evaluating whether a slightly higher down payment changes your payment enough to matter, or checking whether a personal loan payment fits your budget before applying.
Use the amortization table when you want to see cumulative interest in year one, track when balance drops below a target, or explain to a co-borrower how payments split between principal and interest over time. Pair it with the home affordability calculator when moving from income-based budgeting to a specific loan amount.
Related calculators
For vehicle purchases with trade-in, sales tax, and down payment, use the auto loan calculator. To compare keeping your current loan versus replacing it, try the refinance calculator. The home affordability calculator works backward from income and debts to an estimated price range. A HELOC calculator helps model home equity lines separately from a full mortgage payment. For unsecured borrowing with different terms, see the personal loan calculator.
FAQ
What is included in this loan payment estimate?
The estimate covers principal and interest only, based on the loan amount, annual interest rate, and term you enter. It does not include property taxes, homeowners insurance, mortgage insurance, HOA dues, closing costs, or lender fees. For a complete mortgage budget, add those costs separately or use a home affordability calculator that includes housing-related expenses.
Why does total interest change so much with the term?
A longer term spreads the same principal over more monthly payments, which lowers each payment but keeps a balance outstanding longer. Interest accrues on that balance every month, so more months usually mean more total interest even at the same rate. A shorter term raises the payment but cuts the interest window substantially on large loans.
Is the amortization schedule exact?
It follows standard monthly amortization from your inputs and should match most fixed-rate loan illustrations closely. Actual lender schedules can differ because of rounding rules, payment due dates, fees, escrow items, or promotional periods. Use the schedule for planning and comparison, then verify against an official loan estimate or disclosure before signing.
Can I use this for mortgages and personal loans?
Yes. The same principal-and-interest formula applies to many fixed-rate installment loans when payments are equal and monthly. Enter the amount actually borrowed after any down payment. Mortgage-specific costs like taxes and insurance are excluded, so the result is the P&I portion of your housing payment rather than full PITI.
How do I compare a 15-year and 30-year mortgage?
Run the calculator twice with the same loan amount and rate but different terms. The 15-year version typically shows a higher monthly payment and lower total interest. The 30-year version lowers the monthly payment but often increases lifetime interest. Compare both the payment you can afford and the total cost you are willing to accept.
Does this calculator include extra principal payments?
No. It models equal fixed payments for the full term with no prepayments. Extra principal payments would shorten the actual payoff timeline and reduce total interest compared with the schedule shown. You can still use the baseline schedule to see how much of each standard payment goes to principal at different points.
Should I enter APR or the note rate?
Enter the note rate from your loan offer—the stated interest rate used to calculate your payment. APR is designed to reflect borrowing cost more completely by incorporating certain fees, but this calculator applies the rate you type directly to the principal. If you want to compare effective costs including fees, review APR on your loan documents separately.
What happens if I enter a 0% interest rate?
The calculator divides the principal evenly across all payments in the term, producing a simple straight-line payment with no interest charge. Zero-rate promotional auto or medical financing sometimes works this way for a limited period. Verify whether your real offer has deferred interest or fees that this model does not capture.
How should I read the balance chart?
The chart plots remaining loan balance over time using the same amortization math as the table. Steeper decline means more principal paid down per month, which happens later in the loan or with shorter terms. Use it to visualize how slowly equity builds through principal paydown alone in the early years of a long mortgage.
What are the main limitations?
This tool does not model adjustable rates, interest-only periods, balloon payments, prepayment penalties, biweekly payment plans, or variable extra payments. It assumes the rate stays fixed for the entire term. Actual costs may differ when fees are financed, rates adjust, or you pay off early. Treat results as estimates, not binding loan quotes.