Calculate loan or mortgage
calculate_loanRead-onlyIdempotent
Use this when the user wants a mortgage calculator, loan calculator, or amortization calculator result: the monthly (or biweekly/weekly) payment, an amortization schedule or table, total interest, payoff date, a mortgage calculator with extra payments or for paying off early, or a full PITI payment with property tax, insurance, HOA and PMI. Takes the loan amount or home price with down payment, rate, and term. Returns exact payment, totals, interest and time saved by extra payments, a yearly summary, and a CSV of the full schedule. Fixed-rate loans only; does not model adjustable rates, interest-only or balloon loans, and does not look up current rates. Do not use for rent-vs-buy advice or choosing a lender.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| currency | No | ISO 4217 currency code for formatting, e.g. USD, EUR, GBP. Default USD. | |
| pmi_rate | No | Yearly private mortgage insurance rate as a percent of the original loan, e.g. 0.5. Needs home_price. Charged only while the loan is above 80% of the home value, and dropped once the balance reaches 78%. | |
| principal | No | Loan amount to borrow, e.g. 350000. Give this OR home_price with a down payment. | |
| home_price | No | Purchase price or current home value, e.g. 400000. Used with down_payment/down_payment_percent to get the loan amount, and as the value for PMI loan-to-value. | |
| start_date | No | Date of the first payment, YYYY-MM or YYYY-MM-DD, e.g. 2026-11. Defaults to the first day of next month. | |
| term_years | No | Loan term in years, e.g. 30. Give term_years or term_months. | |
| accelerated | No | For biweekly/weekly only: true pays half (biweekly) or a quarter (weekly) of the monthly payment each period, which adds about one extra monthly payment a year. Default false (a true biweekly/weekly amortization). | |
| annual_rate | No | Annual interest rate in percent (nominal APR used for the payment), e.g. 6.5 for 6.5%. 0 is allowed. | |
| hoa_monthly | No | Monthly HOA dues, e.g. 75. | |
| term_months | No | Loan term in months, e.g. 360 or 72 for a car loan. | |
| down_payment | No | Down payment amount, e.g. 50000. Used with home_price. | |
| extra_payment | No | Extra principal paid with every payment, e.g. 200 for $200 more each month. | |
| one_time_payments | No | Lump-sum extra payments, e.g. [{"date":"2030-01","amount":10000}]. | |
| payment_frequency | No | How often payments are made: monthly (default), biweekly (every 2 weeks, 26 a year), or weekly (52 a year). | |
| property_tax_annual | No | Yearly property tax for the PITI breakdown, e.g. 4800. | |
| down_payment_percent | No | Down payment as a percent of home_price, e.g. 20 for 20%. | |
| home_insurance_annual | No | Yearly homeowners insurance for the PITI breakdown, e.g. 1500. |
Output Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| pmi | Yes | ||
| piti | Yes | ||
| chart | Yes | ||
| inputs | Yes | ||
| yearly | Yes | ||
| payment | Yes | ||
| summary | Yes | ||
| currency | Yes | ||
| warnings | Yes | ||
| downloads | Yes | ||
| total_pmi | Yes | ||
| home_price | Yes | ||
| total_paid | Yes | ||
| vs_monthly | Yes | ||
| accelerated | Yes | ||
| annual_rate | Yes | ||
| loan_amount | Yes | ||
| payoff_date | Yes | ||
| term_months | Yes | ||
| final_payment | Yes | ||
| extra_payments | Yes | ||
| payments_count | Yes | ||
| total_interest | Yes | ||
| total_principal | Yes | ||
| payment_frequency | Yes | ||
| first_payment_date | Yes |