{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"loan-payment"},"result":{"entity_type":"calculator","id":"loan-payment","calculator_id":"loan-payment","canonical_url":"https://tttkmbb.com/finance/loan-payment","name":"Loan Payment Calculator","title":"Loan Payment Calculator – Monthly Payment and Total Interest of an Amortizing Loan","category":"finance","category_name":"Finance","tool_name":"calculate_loan_payment","featured_mcp_tool":true,"description":"Computes the level monthly payment of a fully amortizing fixed-rate loan from principal, annual rate and term, plus the total paid and total interest over the life of the loan.","use_when":"You need the monthly payment or total interest cost of an auto, personal, student or other fixed-rate installment loan given its amount, APR and term.","do_not_use_when":"You need property tax, insurance and HOA in the payment (use mortgage-payment), or you know the payment and want the payoff time (use debt-payoff).","inputs":[{"name":"principal","label":"Loan amount","type":"number","required":true,"max":1000000000000,"exclusive_min":0,"description":"Amount borrowed.","example":200000},{"name":"annual_rate_percent","label":"Annual interest rate (APR)","type":"number","unit":"%","required":true,"min":0,"max":100,"description":"Nominal annual rate in percent; the monthly rate is this / 12. 0 is allowed for interest-free loans.","example":6},{"name":"term_years","label":"Term (years)","type":"number","unit":"years","required":false,"min":0,"max":100,"description":"Loan term in years; fractional values allowed. Added to term_months when both are given.","example":30},{"name":"term_months","label":"Term (months)","type":"integer","unit":"months","required":false,"default":0,"min":0,"max":1200,"description":"Additional months of term (e.g. term_months=60 alone for a 5-year auto loan).","example":0}],"outputs":[{"name":"monthly_payment","label":"Monthly payment","type":"number","decimals":2,"description":"Level payment due each month (principal + interest)."},{"name":"number_of_payments","label":"Number of payments","type":"integer","decimals":0,"description":"Total months = 12 × term_years + term_months."},{"name":"total_payment","label":"Total of all payments","type":"number","decimals":2,"description":"monthly_payment × number_of_payments (unrounded payment)."},{"name":"total_interest","label":"Total interest","type":"number","decimals":2,"description":"total_payment − principal."},{"name":"payoff_summary","label":"Payoff summary","type":"string","decimals":4,"description":"Plain-language summary of the schedule."}],"input_schema":{"type":"object","properties":{"principal":{"description":"Amount borrowed.","type":"number","maximum":1000000000000,"exclusiveMinimum":0,"examples":[200000]},"annual_rate_percent":{"description":"Nominal annual rate in percent; the monthly rate is this / 12. 0 is allowed for interest-free loans. Unit: %.","type":"number","minimum":0,"maximum":100,"examples":[6],"x-unit":"%"},"term_years":{"description":"Loan term in years; fractional values allowed. Added to term_months when both are given. Unit: years.","type":"number","minimum":0,"maximum":100,"examples":[30],"x-unit":"years"},"term_months":{"description":"Additional months of term (e.g. term_months=60 alone for a 5-year auto loan). Unit: months.","type":"integer","minimum":0,"maximum":1200,"default":0,"examples":[0],"x-unit":"months"}},"additionalProperties":false,"required":["principal","annual_rate_percent"]},"output_schema":{"type":"object","properties":{"monthly_payment":{"description":"Level payment due each month (principal + interest).","type":"number"},"number_of_payments":{"description":"Total months = 12 × term_years + term_months.","type":"integer"},"total_payment":{"description":"monthly_payment × number_of_payments (unrounded payment).","type":"number"},"total_interest":{"description":"total_payment − principal.","type":"number"},"payoff_summary":{"description":"Plain-language summary of the schedule.","type":"string"}}},"formula":"i = annual_rate_percent / 1200; n = 12·term_years + term_months; monthly_payment = principal × i / (1 − (1 + i)^−n); if i = 0, monthly_payment = principal / n. total_payment = monthly_payment × n; total_interest = total_payment − principal.","method":"Standard annuity (amortization) formula with monthly compounding and payments at the end of each month, as used for US fixed-rate consumer loans. Lenders round the payment to cents and adjust the final payment, so real totals can differ by a few cents.","sources":[{"name":"Wikipedia – Amortization calculator (annuity payment formula)","url":"https://en.wikipedia.org/wiki/Amortization_calculator","type":"reference","retrieved_at":"2026-09-23"},{"name":"Investopedia – Amortization: Definition, Formula and Example","url":"https://www.investopedia.com/terms/a/amortization.asp","type":"reference","retrieved_at":"2026-09-23"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"200,000 at 6 % for 30 years","inputs":{"principal":200000,"annual_rate_percent":6,"term_years":30},"expected":{"monthly_payment":1199.1,"number_of_payments":360,"total_payment":431676.38,"total_interest":231676.38},"url":"https://tttkmbb.com/api/v1/calculate/loan-payment?principal=200000&annual_rate_percent=6&term_years=30"},{"name":"25,000 auto loan at 7 % for 60 months","inputs":{"principal":25000,"annual_rate_percent":7,"term_months":60},"expected":{"monthly_payment":495.03,"number_of_payments":60,"total_payment":29701.8,"total_interest":4701.8},"url":"https://tttkmbb.com/api/v1/calculate/loan-payment?principal=25000&annual_rate_percent=7&term_months=60"}],"faq":[{"q":"Is the APR the same as the interest rate used here?","a":"The formula uses the note rate divided by 12. A lender's disclosed APR also folds in fees, so if you enter the APR the payment will be slightly overstated when fees are large."},{"q":"What if the rate is 0 %?","a":"The annuity formula divides by zero, so the calculator returns principal / number_of_payments instead (e.g. 12,000 over 12 months = 1,000 per month)."},{"q":"How do I model extra payments?","a":"This calculator assumes the fixed schedule only. Use debt-payoff with the higher payment to see the shortened payoff time and interest saved."}],"tags":["loan payment","monthly payment","amortization","auto loan","personal loan","total interest"],"related":[{"calculator_id":"mortgage-payment","reason":"Same amortization plus taxes, insurance and HOA for a home purchase."},{"calculator_id":"debt-payoff","reason":"Given a payment, find how long a balance takes to clear."},{"calculator_id":"apy","reason":"Effective annual cost of a nominal rate with monthly compounding."}],"links":{"html":"https://tttkmbb.com/finance/loan-payment","markdown":"https://tttkmbb.com/finance/loan-payment.md","json":"https://tttkmbb.com/finance/loan-payment.json","api":"https://tttkmbb.com/api/v1/calculate/loan-payment","schema":"https://tttkmbb.com/api/v1/calculators/loan-payment","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:29:57Z","next_actions":[{"tool":"calculate_loan_payment","calculator_id":"loan-payment","reason":"Run Loan Payment Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/finance/loan-payment.md"}}