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The math the dealer skips.Free. No signup.

Calculators built around the parts of an auto deal where the markup actually lives: term length, depreciation, and money factor. The kind of thing you wish you'd run before walking into F&I.

60 / 72 / 84 months, side by side, with underwater months

Auto loan true-cost calculator

Compare three loan terms at once. See total interest, monthly payment, and the months your car is worth less than what you owe. The only calculator that visualizes the underwater region.

  • ·60, 72, and 84-month comparison cards
  • ·Loan balance vs depreciated value chart
  • ·Underwater-months shaded region
  • ·Negative-equity rollover math
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Money factor → APR, plus the dealer markup banner

Car lease calculator with markup detection

Pick the captive lender (BMW Financial, Toyota Financial, etc.) and we compare your quoted money factor to their published base rate. See the dollar markup per month and over the lease.

  • ·Money factor → APR conversion (the 2400 rule)
  • ·Dealer-reserve markup banner with $/mo and $/term
  • ·Negotiable vs fixed tags on every input
  • ·Plain-English breakdown of every dollar
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3, 5, and 7-year holds — with replacement cycles and retained equity

Lease vs buy total-cost calculator

Side-by-side at current rates. Models lease replacement cycles every 36 months and subtracts the depreciated car value from the buy side — the only fair way to compare a wasting lease against a financed asset.

  • ·Total cost of ownership across 3 / 5 / 7-year holds
  • ·Lease cycles restart with a new cap reduction each time
  • ·Retained equity subtracted from the buy side
  • ·Cumulative-cost chart with the crossover month marked
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The app

The contract is where the rest lives.

The calculators show the math. Redline reads the actual contract. Photograph the buyer's order, the lease worksheet, or any agreement, and Redline flags hidden fees, mandatory arbitration, and the clauses that change the deal's economics in plain English.

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