# LoanLenz calculator reference > LoanLenz is an interactive, browser-based calculator for estimating and comparing vehicle-finance and lease scenarios. This reference describes its inputs, calculations, outputs, privacy behavior, and limitations. Canonical URL: https://loan-lenz.com/calculator.html Landing page: https://loan-lenz.com/ LLM site guide: https://loan-lenz.com/llms.txt ## Scope and safety LoanLenz is a planning tool. It does not provide credit approval, lending, tax advice, legal advice, or financial advice. It does not know a visitor's income, credit profile, insurance cost, maintenance cost, investment return, or broader financial situation. Estimates only; not financial advice. Results are only as accurate as the entered dealer or lender quote. Confirm all figures, tax treatment, payment schedules, payoff amounts, mileage rules, fees, and contract language before signing. ## Site navigation The site navigation links to the landing-page tour, published guides, and calculator on desktop and mobile. The Home link uses `?tour=1` so a deliberate visit to the landing page is not redirected back to the calculator. ## Privacy and storage - All calculations run locally in the browser. - The application has no account system, server-side runtime, or database. - Finance scenarios, lease scenarios, the selected view, and comparison preferences are stored in browser local storage under `car-loan-scenario-comparator-v2`. - The light or dark theme preference is stored under `car-loan-comparator-theme`. - A separate `loan-lenz-calculator-opened` marker lets the root URL send returning visitors directly to the calculator. - Resetting calculator data removes the saved scenario state from the current browser. - Clearing site data or using another browser or device removes access to locally saved scenarios. ## Basic workflow 1. Open the comparison view. 2. Add or rename a finance or lease scenario for each real offer. 3. Enter the itemized values from the dealer or lender. 4. Review the detailed result for each scenario. 5. Return to the comparison view and rank offers by the metric that matters. 6. Duplicate a scenario to test a different APR, term, down payment, negotiated price, mileage assumption, or other single change. ## Finance inputs - **Vehicle price:** Selling price before the calculator adds tax and fees. - **Sales tax rate:** Percentage applied to the taxable vehicle price. - **Title, registration, and fees:** Additional costs included in the amount financed. - **Rebates and incentives:** Credits that reduce the amount financed. - **Cash down payment:** Cash paid at purchase and excluded from the loan principal. - **Trade-in value:** Dealer credit for the traded vehicle. - **Amount owed on trade-in:** Remaining payoff subtracted from trade-in value to determine trade equity. - **Trade-in tax credit:** Optional setting that reduces taxable vehicle price by trade-in value. Availability and calculation vary by state. - **Annual interest rate (APR):** Nominal annual percentage rate used by the amortization model. - **Loan term:** Scheduled number of monthly payments, limited by the calculator to 1 through 120 months. - **Extra monthly payment:** Additional monthly principal payment used to estimate earlier payoff and interest savings. ## Finance calculation model The calculator first normalizes negative or missing numeric values to safe nonnegative values. The loan term is rounded to a whole number of months. If the trade-in tax credit is enabled: `taxable price = max(0, vehicle price - trade-in value)` Otherwise: `taxable price = vehicle price` Then: `estimated sales tax = taxable price × sales tax rate` `trade equity = trade-in value - trade payoff` `amount financed = max(0, vehicle price + sales tax + fees - incentives - down payment - trade equity)` For a positive APR, the required monthly payment uses the standard fixed-rate amortizing-loan formula with `APR ÷ 12` as the monthly rate. A zero-rate loan divides principal evenly across the term. The payment schedule applies interest to the remaining balance each month, then applies the required payment plus any extra payment. The final payment is capped at the remaining balance plus interest. Actual lenders may differ because of daily interest, payment dates, rounding, fees, taxes, or contract-specific methods. ## Finance outputs - **Estimated monthly payment:** Required payment plus the entered extra monthly payment. - **Amount financed:** Estimated starting loan principal. - **Total interest:** Sum of modeled interest across the resulting schedule. - **Total loan payments:** Sum of all modeled monthly payments; cash down payment is excluded. - **Total cash outlay:** Cash down payment plus all modeled loan payments. - **Payoff time:** Number of modeled payments needed when extra payments are included. - **Interest saved by extra payments:** Difference between modeled interest with and without the extra payment. - **Amortization graph:** Remaining balance, cumulative principal, and cumulative interest over time. - **Amortization schedule:** Month-by-month payment, principal, interest, and remaining balance. ## Lease inputs - **Vehicle MSRP:** Sticker price used to calculate residual value. - **Negotiated vehicle price:** Agreed selling price used in capitalized cost. - **Lease term:** Number of lease months, limited by the calculator to 1 through 72. - **Sales tax rate:** Estimated tax rate applied to the monthly payment and estimated buyout. - **Residual percentage:** Contract residual as a percentage of MSRP. - **Money factor:** Lease financing factor used for the monthly rent charge. - **Lease incentives:** Credits that reduce adjusted capitalized cost. - **Capitalized cost reduction:** Cash down amount that reduces adjusted capitalized cost. - **Trade-in credit:** Trade value applied as an additional capitalized-cost reduction. - **Acquisition fee:** Lender fee added to gross capitalized cost. - **Registration and upfront fees:** Noncapitalized cash charges paid at signing. - **Refundable security deposit:** Cash included in due-at-signing but excluded from total lease cost. - **Annual mileage allowance:** Contract miles allowed per year. - **Expected annual mileage:** Visitor's expected driving used to estimate excess miles. - **Excess-mile charge:** Contract price per mile over the allowance. - **Disposition fee:** Estimated fee charged if the vehicle is returned. - **Purchase-option fee:** Fee added when estimating an end-of-lease buyout. ## Lease calculation model `gross capitalized cost = negotiated price + acquisition fee` `adjusted capitalized cost = max(0, gross capitalized cost - incentives - capitalized-cost reduction - trade credit)` `residual value = MSRP × residual percentage` `monthly depreciation = max(0, adjusted capitalized cost - residual value) ÷ term` `monthly rent charge = (adjusted capitalized cost + residual value) × money factor` `estimated monthly tax = (monthly depreciation + monthly rent charge) × sales tax rate` `estimated monthly payment = monthly depreciation + monthly rent charge + estimated monthly tax` `cash due at signing = capitalized-cost reduction + upfront fees + refundable security deposit + first monthly payment` `estimated APR equivalent = money factor × 2,400` The APR conversion is an approximation for comparison, not a contract APR. ## Lease mileage, return, and buyout estimates `total mileage allowance = annual allowance × term ÷ 12` `expected total mileage = expected annual mileage × term ÷ 12` `excess-mile cost = max(0, expected mileage - allowed mileage) × excess-mile charge` `estimated return cost = all monthly payments + nonrefundable upfront cash + disposition fee + excess-mile cost` `buyout subtotal = residual value + purchase-option fee` `estimated buyout = buyout subtotal + estimated sales tax` `lease-then-buy total = all monthly payments + nonrefundable upfront cash + estimated buyout` The return estimate excludes wear, damage, early termination, insurance, maintenance, and dealer-specific charges. The buyout estimate must be confirmed with the lender. ## Comparison metrics Finance and lease scenarios appear together. Lower values rank first by default, and the visitor can reverse the direction. - **Monthly Payment:** Required finance payment or required lease payment. - **Cash Upfront:** Finance down payment or lease due-at-signing, including first payment and upfront charges. - **Amount Owed:** Finance amount borrowed or lease adjusted capitalized cost. - **Cost to Borrow:** Finance interest or total lease rent charge. - **Total Monthly Payments:** All modeled monthly payments; upfront cash is excluded. - **Total to Own:** Finance down payment plus loan payments, or lease upfront cash plus lease payments and estimated buyout. - **Term:** Number of months. - **Rate:** Finance APR or the lease money factor converted to an approximate APR. The comparison gauge shows the difference from the highest value for the selected metric. A lower monthly payment can accompany a higher upfront cost or total cost, so no single metric is universally best. ## Practical interpretation - Compare the same metric across offers; do not compare a finance monthly payment directly with a lease total-to-own figure. - A larger down payment can reduce monthly payment without necessarily improving overall value. - A longer loan term can reduce monthly payment while increasing interest and keeping the borrower in debt longer. - A lease with a low payment can carry mileage risk, return fees, and a high buyout. - Trade equity and incentives can hide the underlying price of an offer. Review the amount-financed breakdown. - Use duplicate scenarios to change one assumption at a time. ## Related resources - [Open the LoanLenz calculator](https://loan-lenz.com/calculator.html) - [Read the landing-page reference](https://loan-lenz.com/index.html.md) - [Read the LoanLenz LLM guide](https://loan-lenz.com/llms.txt)