{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"loan-comparison"},"result":{"entity_type":"calculator","id":"loan-comparison","calculator_id":"loan-comparison","canonical_url":"https://tttkmbb.com/finance/loan-comparison","name":"Loan Comparison Calculator","title":"Loan Comparison Calculator – Monthly Payment, Total Interest and Total Cost of Two Loan Offers","category":"finance","category_name":"Finance","tool_name":"compare_loans","featured_mcp_tool":false,"description":"Compares two fixed-rate, fully amortizing loan offers for the same amount: the level monthly payment, total interest, up-front fees and total cost (interest + fees) of each, and which offer costs less over its full term.","use_when":"You have two loan or mortgage quotes with different rates, terms or fees for the same amount and want the payments and lifetime costs side by side.","do_not_use_when":"You are replacing an existing loan (use refinance-break-even), only need one loan's payment (use loan-payment), or will sell or repay early (this compares full-term costs and ignores the time value of money). Informational; not financial advice.","inputs":[{"name":"loan_amount","label":"Loan amount","type":"number","required":true,"max":1000000000000,"exclusive_min":0,"description":"Amount borrowed under both offers.","example":300000},{"name":"rate_a_percent","label":"Loan A interest rate","type":"number","unit":"%","required":true,"min":0,"max":100,"description":"Annual nominal rate of loan A in percent; the monthly rate is this / 12.","example":6},{"name":"term_a_years","label":"Loan A term","type":"number","unit":"years","required":true,"max":100,"exclusive_min":0,"description":"Term of loan A in years (fractions allowed; rounded to whole months).","example":30},{"name":"fees_a","label":"Loan A fees","type":"number","required":false,"default":0,"min":0,"max":1000000000,"description":"Up-front fees of loan A (origination, points, closing costs), paid separately rather than financed.","example":3000},{"name":"rate_b_percent","label":"Loan B interest rate","type":"number","unit":"%","required":true,"min":0,"max":100,"description":"Annual nominal rate of loan B in percent.","example":5.5},{"name":"term_b_years","label":"Loan B term","type":"number","unit":"years","required":true,"max":100,"exclusive_min":0,"description":"Term of loan B in years.","example":15},{"name":"fees_b","label":"Loan B fees","type":"number","required":false,"default":0,"min":0,"max":1000000000,"description":"Up-front fees of loan B.","example":5000}],"outputs":[{"name":"payment_a","label":"Loan A monthly payment","type":"number","decimals":2,"description":"Level monthly payment of loan A (annuity formula)."},{"name":"payment_b","label":"Loan B monthly payment","type":"number","decimals":2,"description":"Level monthly payment of loan B."},{"name":"total_interest_a","label":"Loan A total interest","type":"number","decimals":2,"description":"payment_a × months_a − loan_amount."},{"name":"total_interest_b","label":"Loan B total interest","type":"number","decimals":2,"description":"payment_b × months_b − loan_amount."},{"name":"total_cost_a","label":"Loan A total cost","type":"number","decimals":2,"description":"total_interest_a + fees_a: what loan A costs beyond repaying the principal."},{"name":"total_cost_b","label":"Loan B total cost","type":"number","decimals":2,"description":"total_interest_b + fees_b."},{"name":"cheaper_loan","label":"Cheaper loan","type":"string","decimals":4,"description":"\"A\", \"B\" or \"equal\" by total cost (interest + fees), compared to the cent."},{"name":"monthly_payment_difference","label":"Monthly payment difference","type":"number","decimals":2,"description":"payment_a − payment_b (positive = loan A has the higher monthly payment)."},{"name":"total_cost_difference","label":"Total cost difference","type":"number","decimals":2,"description":"total_cost_a − total_cost_b (positive = loan A costs more over its full term)."},{"name":"comparison","label":"Comparison table","type":"list","decimals":2,"description":"Two rows: loan, rate_percent, term_years, monthly_payment, total_interest, fees, total_cost."},{"name":"summary","label":"Summary","type":"string","decimals":4,"description":"Plain-language comparison of payment and lifetime cost."}],"input_schema":{"type":"object","properties":{"loan_amount":{"description":"Amount borrowed under both offers.","type":"number","maximum":1000000000000,"exclusiveMinimum":0,"examples":[300000]},"rate_a_percent":{"description":"Annual nominal rate of loan A in percent; the monthly rate is this / 12. Unit: %.","type":"number","minimum":0,"maximum":100,"examples":[6],"x-unit":"%"},"term_a_years":{"description":"Term of loan A in years (fractions allowed; rounded to whole months). Unit: years.","type":"number","maximum":100,"exclusiveMinimum":0,"examples":[30],"x-unit":"years"},"fees_a":{"description":"Up-front fees of loan A (origination, points, closing costs), paid separately rather than financed.","type":"number","minimum":0,"maximum":1000000000,"default":0,"examples":[3000]},"rate_b_percent":{"description":"Annual nominal rate of loan B in percent. Unit: %.","type":"number","minimum":0,"maximum":100,"examples":[5.5],"x-unit":"%"},"term_b_years":{"description":"Term of loan B in years. Unit: years.","type":"number","maximum":100,"exclusiveMinimum":0,"examples":[15],"x-unit":"years"},"fees_b":{"description":"Up-front fees of loan B.","type":"number","minimum":0,"maximum":1000000000,"default":0,"examples":[5000]}},"additionalProperties":false,"required":["loan_amount","rate_a_percent","term_a_years","rate_b_percent","term_b_years"]},"output_schema":{"type":"object","properties":{"payment_a":{"description":"Level monthly payment of loan A (annuity formula).","type":"number"},"payment_b":{"description":"Level monthly payment of loan B.","type":"number"},"total_interest_a":{"description":"payment_a × months_a − loan_amount.","type":"number"},"total_interest_b":{"description":"payment_b × months_b − loan_amount.","type":"number"},"total_cost_a":{"description":"total_interest_a + fees_a: what loan A costs beyond repaying the principal.","type":"number"},"total_cost_b":{"description":"total_interest_b + fees_b.","type":"number"},"cheaper_loan":{"description":"\"A\", \"B\" or \"equal\" by total cost (interest + fees), compared to the cent.","type":"string"},"monthly_payment_difference":{"description":"payment_a − payment_b (positive = loan A has the higher monthly payment).","type":"number"},"total_cost_difference":{"description":"total_cost_a − total_cost_b (positive = loan A costs more over its full term).","type":"number"},"comparison":{"description":"Two rows: loan, rate_percent, term_years, monthly_payment, total_interest, fees, total_cost.","type":"array"},"summary":{"description":"Plain-language comparison of payment and lifetime cost.","type":"string"}}},"formula":"For each loan: i = rate/1200, n = 12 × term_years, payment = loan_amount × i / (1 − (1 + i)^−n) (loan_amount / n if i = 0); total_interest = payment × n − loan_amount; total_cost = total_interest + fees. cheaper_loan = the loan with the lower total_cost; monthly_payment_difference = payment_a − payment_b; total_cost_difference = total_cost_a − total_cost_b","method":"Standard monthly amortization with end-of-month payments, both loans held to maturity, fees paid up front and not financed. A shorter term raises the payment but lowers lifetime interest; the comparison does not discount future payments, so it favours shorter terms when cash flow is not a constraint.","sources":[{"name":"Wikipedia – Amortization calculator (annuity payment formula)","url":"https://en.wikipedia.org/wiki/Amortization_calculator","type":"reference","retrieved_at":"2026-09-24"},{"name":"CFPB – How do mortgage lenders calculate monthly payments?","url":"https://www.consumerfinance.gov/ask-cfpb/how-do-mortgage-lenders-calculate-monthly-payments-en-1965/","type":"government","retrieved_at":"2026-09-24"},{"name":"CFPB – Owning a Home: compare loan offers","url":"https://www.consumerfinance.gov/owning-a-home/","type":"government","retrieved_at":"2026-09-24"}],"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":"300,000: A 6 % for 30 years with 3,000 fees vs B 5.5 % for 15 years with 5,000 fees","inputs":{"loan_amount":300000,"rate_a_percent":6,"term_a_years":30,"fees_a":3000,"rate_b_percent":5.5,"term_b_years":15,"fees_b":5000},"expected":{"payment_a":1798.65,"payment_b":2451.25,"total_interest_a":347514.57,"total_interest_b":141225.07,"total_cost_a":350514.57,"total_cost_b":146225.07,"cheaper_loan":"B","monthly_payment_difference":-652.6,"total_cost_difference":204289.5},"url":"https://tttkmbb.com/api/v1/calculate/loan-comparison?loan_amount=300000&rate_a_percent=6&term_a_years=30&fees_a=3000&rate_b_percent=5.5&term_b_years=15&fees_b=5000"},{"name":"25,000 auto loan: A 7 % for 5 years, no fees vs B 6 % for 6 years with 500 fees","inputs":{"loan_amount":25000,"rate_a_percent":7,"term_a_years":5,"rate_b_percent":6,"term_b_years":6,"fees_b":500},"expected":{"payment_a":495.03,"payment_b":414.32,"total_interest_a":4701.8,"total_interest_b":4831.2,"total_cost_a":4701.8,"total_cost_b":5331.2,"cheaper_loan":"A","monthly_payment_difference":80.71,"total_cost_difference":-629.4},"url":"https://tttkmbb.com/api/v1/calculate/loan-comparison?loan_amount=25000&rate_a_percent=7&term_a_years=5&rate_b_percent=6&term_b_years=6&fees_b=500"}],"faq":[{"q":"Why is the loan with the higher payment the cheaper one?","a":"Total cost counts interest over the whole term: a 15-year loan repays principal faster, so interest accrues on a smaller balance for fewer months, even though each payment is larger."},{"q":"How do fees enter the comparison?","a":"They are added to total interest to form total_cost and are assumed paid in cash at closing. To model financed fees, add them to loan_amount for that offer and run loan-payment separately."},{"q":"Should I compare APRs instead?","a":"An APR folds fees into a single rate over the full term and is useful for offers with the same term; for different terms the total-cost view here shows the trade-off between payment size and lifetime interest directly."}],"tags":["loan comparison","compare loans","compare mortgage offers","total cost of loan","15 vs 30 year mortgage","loan fees"],"related":[{"calculator_id":"loan-payment","reason":"Payment and totals of a single loan."},{"calculator_id":"refinance-break-even","reason":"Compare a new loan against the remaining term of an existing one."},{"calculator_id":"amortization-schedule","reason":"Year-by-year balance of either offer."}],"links":{"html":"https://tttkmbb.com/finance/loan-comparison","markdown":"https://tttkmbb.com/finance/loan-comparison.md","json":"https://tttkmbb.com/finance/loan-comparison.json","api":"https://tttkmbb.com/api/v1/calculate/loan-comparison","schema":"https://tttkmbb.com/api/v1/calculators/loan-comparison","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:44:37Z"}