Methodology
The calculator builds a payment-by-payment schedule, applies periodic interest before principal, caps the final payment at the remaining balance and accrued interest, and keeps escrow costs separate from loan interest. Fixed-rate payments use the selected rate, term, payment frequency, and compounding convention. Variable-rate plans re-amortize the remaining balance when a new rate becomes effective. Extra principal is applied after the scheduled payment. Offer comparison uses the same cost framework across up to three loans, while refinance mode compares payment savings, closing costs, break-even time, expected holding-period savings, and estimated lifetime cost.
Assumptions
- The entered balance, rates, term, payment frequency, fees, escrow, extra payments, and rate-change schedule remain as entered unless the user changes them.
- Scheduled payments occur on the generated dates and extra principal is applied after scheduled interest and principal.
- Property tax, insurance, HOA, PMI, and other escrow values are treated as out-of-pocket costs rather than interest or principal.
- Refinance results assume the entered closing costs and holding period and do not model future changes that are not entered.
- Currency selection changes formatting only and does not convert amounts.
Limitations
- Lenders may use different day-count conventions, compounding methods, payment timing, rounding, fee treatment, and escrow rules.
- The model does not automatically include every origination fee, prepayment penalty, late fee, tax consequence, adjustable-rate cap, or lender-specific contract term.
- Interest-only and balloon structures may leave principal due at the end of the selected period; the displayed remainder is not a lender payoff quote.
- Refinance break-even and lifetime-cost results are planning estimates and may differ from lender disclosures or actual closing documents.
- The output is educational information and not financial, credit, mortgage, legal, or tax advice.
How do I calculate my monthly loan payment?
For a standard fixed-rate loan, enter the amount financed, annual interest rate, and term. Choose monthly payments and the matching compounding convention, then review the payment, total interest, and amortization schedule. Enter the contract interest rate—not an APR that includes fees as though it were the interest rate. Add fees separately and use the APR vs. APY guide to distinguish borrowing disclosures from savings yields.
For equal end-of-month payments with monthly compounding, the formula is M = P × r ÷ (1 − (1 + r)^(−n)): P is principal, r is the nominal annual interest rate divided by 12, and n is the number of monthly payments. At 0% interest, use P ÷ n instead. This formula does not cover every variable-rate, daily-interest, interest-only, or balloon contract.
Worked example: 10,000 over three years
A 10,000 loan at a fixed nominal annual rate of 6%, compounded monthly over 36 end-of-month payments, has a principal-and-interest payment of approximately 304.22 per month. With no fees, escrow, or extra payments, total interest is about 951.90. Figures use unrounded model payments; actual cents and the final payment can differ with lender rounding. At 0%, the same principal and term would require approximately 277.78 per month and no interest.
What should I check in the results?
Payment is the recurring cash commitment; total interest is the financing cost from interest alone. Check the remaining balance and payoff date as well. Fees and escrow can increase out-of-pocket cost without reducing principal. Test an extra-payment scenario, then make sure that payment fits your monthly budget. A lower payment from a longer term is not automatically a cheaper loan.
Choose the decision you need to model
Use Repayment plan to estimate one loan, Compare offers to review up to three lender quotes with consistent assumptions, or Refinance to test payment savings, closing-cost recovery, holding-period savings, and lifetime cost.
Model the contract, not only the headline rate
Include the loan amount, rate, term, payment frequency, fees, escrow, extra principal, rate changes, interest-only period, or balloon structure that actually applies. Review the amortization schedule and remaining balance rather than relying only on the first payment.
Compare plans with the rest of your finances
A lower payment may extend the term or increase total interest. Compare the result with your monthly budget, cash reserves, debt priorities, and expected time in the loan before choosing a plan.
Privacy, saved scenarios, and share links
The calculator does not require an account. Inputs and saved scenarios remain in local browser storage. A share link reproduces the visible scenario by placing its values in the URL; review the link before sending it. General page-level analytics may record that the page was visited, but they must not receive loan amounts, rates, terms, payments, or other calculator inputs.
