CarLoanMath

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US car loan math: monthly payment, compare loans, max price for your budget, amortization. Free.

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      "updatedAt": "2026-11-13T06:27:21.58741Z",
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    "title": "CarLoanMath",
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    "websiteUrl": "https://carloanmath.com/",
    "description": "US car loan math: monthly payment, compare loans, max price for your budget, amortization. Free."
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amortization_schedule Read-only

Principal, interest and remaining balance over the life of one loan. Yearly summary by default; period 'month' gives every payment (up to 120 rows). When optional inputs are omitted, the result includes assumed_defaults (the values actually used) and a short text line so you can call again with those parameters. assumed_defaults is omitted when every optional input was provided.

aprnumber, required

Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing.

pricenumber, required

Vehicle price in USD (before tax, fees, down payment and trade-in).

term_monthsinteger, required

Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84).

downnumber

Cash down payment in USD. Default 0.

feesnumber

Title, registration, documentation and dealer fees in USD. Default 0.

periodstring

'year' (default) or 'month'.

countrystring

Country of the purchase, ISO 3166-1 alpha-2. Default "US". Only US is available for now.

trade_innumber

Trade-in value in USD credited against the price. Default 0.

sales_tax_ratenumber

Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0.

owed_on_trade_innumber

Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0.

tax_and_fees_financedboolean

false (default, the site's "Pay upfront"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan.

Try it

Call this server's tools from your browser. Nothing to install.

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amortization_schedule Read-only

aprnumber, required

pricenumber, required

Vehicle price in USD (before tax, fees, down payment and trade-in).

term_monthsinteger, required

Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84).

downnumber

Cash down payment in USD. Default 0.

feesnumber

Title, registration, documentation and dealer fees in USD. Default 0.

periodstring

'year' (default) or 'month'.

countrystring

Country of the purchase, ISO 3166-1 alpha-2. Default "US". Only US is available for now.

trade_innumber

Trade-in value in USD credited against the price. Default 0.

sales_tax_ratenumber

Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0.

owed_on_trade_innumber

Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0.

tax_and_fees_financedboolean

false (default, the site's "Pay upfront"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan.

Tools (4)

amortization_schedule

read-only

Argument	Type	Description
apr*	number	Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing.
down	number	Cash down payment in USD. Default 0.
fees	number	Title, registration, documentation and dealer fees in USD. Default 0.
price*	number	Vehicle price in USD (before tax, fees, down payment and trade-in).
period	string	'year' (default) or 'month'.
country	string	Country of the purchase, ISO 3166-1 alpha-2. Default "US". Only US is available for now.
trade_in	number	Trade-in value in USD credited against the price. Default 0.
term_months*	integer	Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84).
sales_tax_rate	number	Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0.
owed_on_trade_in	number	Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0.
tax_and_fees_financed	boolean	false (default, the site's "Pay upfront"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan.

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "price",
    "apr",
    "term_months"
  ],
  "properties": {
    "apr": {
      "type": "number",
      "maximum": 40,
      "minimum": 0,
      "description": "Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing."
    },
    "down": {
      "type": "number",
      "maximum": 10000000,
      "minimum": 0,
      "description": "Cash down payment in USD. Default 0."
    },
    "fees": {
      "type": "number",
      "maximum": 100000,
      "minimum": 0,
      "description": "Title, registration, documentation and dealer fees in USD. Default 0."
    },
    "price": {
      "type": "number",
      "maximum": 10000000,
      "minimum": 0,
      "description": "Vehicle price in USD (before tax, fees, down payment and trade-in)."
    },
    "period": {
      "enum": [
        "year",
        "month"
      ],
      "type": "string",
      "description": "'year' (default) or 'month'."
    },
    "country": {
      "enum": [
        "US"
      ],
      "type": "string",
      "default": "US",
      "description": "Country of the purchase, ISO 3166-1 alpha-2. Default \"US\". Only US is available for now."
    },
    "trade_in": {
      "type": "number",
      "maximum": 10000000,
      "minimum": 0,
      "description": "Trade-in value in USD credited against the price. Default 0."
    },
    "term_months": {
      "type": "integer",
      "maximum": 120,
      "minimum": 1,
      "description": "Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84)."
    },
    "sales_tax_rate": {
      "type": "number",
      "maximum": 20,
      "minimum": 0,
      "description": "Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0."
    },
    "owed_on_trade_in": {
      "type": "number",
      "maximum": 10000000,
      "minimum": 0,
      "description": "Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0."
    },
    "tax_and_fees_financed": {
      "type": "boolean",
      "default": false,
      "description": "false (default, the site's \"Pay upfront\"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan."
    }
  }
}

calculate_auto_loan

Monthly payment, amount financed, total interest and total cost for one US car loan. Amount financed = price − down − trade-in + owed on trade-in; sales tax and fees are paid upfront unless tax_and_fees_financed is true, then they are added to the loan. total_cost = cash due at purchase + all payments (price + tax + fees + interest − trade-in + owed). Returns the inputs echoed back and a carloanmath.com share_url. When optional inputs are omitted, the result includes assumed_defaults (the values actually used) and a short text line so you can call again with those parameters. assumed_defaults is omitted when every optional input was provided.

read-only

Argument	Type	Description
apr*	number	Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing.
down	number	Cash down payment in USD. Default 0.
fees	number	Title, registration, documentation and dealer fees in USD. Default 0.
price*	number	Vehicle price in USD (before tax, fees, down payment and trade-in).
country	string	Country of the purchase, ISO 3166-1 alpha-2. Default "US". Only US is available for now.
trade_in	number

compare_auto_loans

Side-by-side comparison of 2–4 loan scenarios (e.g. 60 vs 72 months, dealer vs credit-union APR, more down). Each result has a share_url; differences are against the first scenario, plus which is cheapest overall and lowest monthly. When optional inputs are omitted, the result includes assumed_defaults (the values actually used) and a short text line so you can call again with those parameters. assumed_defaults is omitted when every optional input was provided. On this tool, assumed_defaults is per scenario; a top-level assumed_defaults is included only when country was omitted.

read-only

Argument	Type	Description
country	string	Country for every scenario, ISO 3166-1 alpha-2. Default "US"; only US is available for now.
scenarios*	array	2–4 scenarios. The first is the baseline for differences.

Input schema (JSON)

{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "scenarios"
  ],
  "properties": {
    "country": {
      "enum": [
        "US"
      ],
      "type": "string",
      "default": "US",
      "description": "Country for every scenario, ISO 3166-1 alpha-2. Default \"US\"; only US is available for now."
    },
    "scenarios": {
      "type": "array",
      "items": {
        "type": "object",
        "required": [
          "price",
          "apr",
          "term_months"
        ],
        "properties": {
          "apr": {
            "type": "number",
            "maximum": 40,
            "minimum": 0,
            "description": "Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing."
          },
          "down": {
            "type": "number",
            "maximum": 10000000,
            "minimum": 0,
            "description": "Cash down payment in USD. Default 0."
          },
          "fees": {
            "type": "number",
            "maximum": 100000,
            "minimum": 0,
            "description": "Title, registration, documentation and dealer fees in USD. Default 0."
          },
          "label": {
            "type": "string",
            "maxLength": 40,
            "description": "Short name, e.g. '72 mo dealer'."
          },
          "price": {
            "type": "number",
            "maximum": 10000000,
            "minimum": 0,
            "description": "Vehicle price in USD (before tax, fees, down payment and trade-in)."
          },
          "trade_in": {
            "type": "number",
            "maximum": 10000000,
            "minimum": 0,
            "description": "Trade-in value in USD credited against the price. Default 0."
          },
          "term_months": {
            "type": "integer",
            "maximum": 120,
            "minimum": 1,
            "description": "Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84)."
          },
          "sales_tax_rate": {
            "type": "number",
            "maximum": 20,
            "minimum": 0,
            "description": "Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0."
          },
          "owed_on_trade_in": {
            "type": "number",
            "maximum": 10000000,
            "minimum": 0,
            "description": "Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0."
          },
          "tax_and_fees_financed": {
            "type": "boolean",
            "default": false,
            "description": "false (default, the site's \"Pay upfront\"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan."
          }
        }
      },
      "maxItems": 4,
      "minItems": 2,
      "description": "2–4 scenarios. The first is the baseline for differences."
    }
  }
}

max_vehicle_price_for_budget

Reverse calculation: the highest vehicle price whose monthly payment stays within monthly_budget, for one or more terms. Uses the same tax, fee, down payment and trade-in rules as calculate_auto_loan. Each row includes the check calculation and its share_url. When optional inputs are omitted, the result includes assumed_defaults (the values actually used) and a short text line so you can call again with those parameters. assumed_defaults is omitted when every optional input was provided.

read-only

Argument	Type	Description
apr*	number	Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing.
down	number	Cash down payment in USD. Default 0.
fees	number	Title, registration, documentation and dealer fees in USD. Default 0.
country	string	Country of the purchase, ISO 3166-1 alpha-2. Default "US". Only US is available for now.
trade_in	number	Trade-in value in USD credited against the price. Default 0.
term_months*	any	One term or a list of up to 8 terms in months, e.g. [48, 60, 72].

{ "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "required": [ "price", "apr", "term_months" ], "properties": { "apr": { "type": "number", "maximum": 40, "minimum": 0, "description": "Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing." }, "down": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Cash down payment in USD. Default 0." }, "fees": { "type": "number", "maximum": 100000, "minimum": 0, "description": "Title, registration, documentation and dealer fees in USD. Default 0." }, "price": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Vehicle price in USD (before tax, fees, down payment and trade-in)." }, "country": { "enum": [ "US" ], "type": "string", "default": "US", "description": "Country of the purchase, ISO 3166-1 alpha-2. Default \"US\". Only US is available for now." }, "trade_in": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Trade-in value in USD credited against the price. Default 0." }, "term_months": { "type": "integer", "maximum": 120, "minimum": 1, "description": "Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84)." }, "sales_tax_rate": { "type": "number", "maximum": 20, "minimum": 0, "description": "Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0." }, "owed_on_trade_in": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0." }, "tax_and_fees_financed": { "type": "boolean", "default": false, "description": "false (default, the site's \"Pay upfront\"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan." } } }

{ "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "required": [ "monthly_budget", "apr", "term_months" ], "properties": { "apr": { "type": "number", "maximum": 40, "minimum": 0, "description": "Yearly interest rate in percent, compounded monthly (the same number as the site’s rate field), e.g. 6.5 for 6.5%. A lender’s APR can be a little higher because it folds in some fees. Use 0 for 0% financing." }, "down": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Cash down payment in USD. Default 0." }, "fees": { "type": "number", "maximum": 100000, "minimum": 0, "description": "Title, registration, documentation and dealer fees in USD. Default 0." }, "country": { "enum": [ "US" ], "type": "string", "default": "US", "description": "Country of the purchase, ISO 3166-1 alpha-2. Default \"US\". Only US is available for now." }, "trade_in": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Trade-in value in USD credited against the price. Default 0." }, "term_months": { "anyOf": [ { "type": "integer", "maximum": 120, "minimum": 1, "description": "Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84)." }, { "type": "array", "items": { "type": "integer", "maximum": 120, "minimum": 1, "description": "Loan term in whole months, 1–120 (common: 36, 48, 60, 72, 84)." }, "maxItems": 8, "minItems": 1 } ], "description": "One term or a list of up to 8 terms in months, e.g. [48, 60, 72]." }, "monthly_budget": { "type": "number", "maximum": 1000000, "minimum": 1, "description": "Most the buyer wants to pay per month, in USD." }, "sales_tax_rate": { "type": "number", "maximum": 20, "minimum": 0, "description": "Sales tax in percent of the vehicle price, e.g. 7 for 7%. No state rules or trade-in tax credit are applied. Default 0." }, "owed_on_trade_in": { "type": "number", "maximum": 10000000, "minimum": 0, "description": "Loan balance still owed on the trade-in, rolled into the new loan (negative equity). Default 0." }, "tax_and_fees_financed": { "type": "boolean", "default": false, "description": "false (default, the site's \"Pay upfront\"): sales tax and fees are paid in cash at purchase, not financed. true: they are added to the loan." } } }

CarLoanMath

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amortization_schedule Read-only

CarLoanMath

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amortization_schedule Read-only

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