AutoMath

Car-cost math, shown

The real cost of a car, made clear.

Free calculators for auto loans, lease-vs-buy, fuel, EV charging, and the full cost of ownership. The math is shown, and it runs in your browser — no accounts, nothing sent to a server.

Run the loan numbers Browse 25 calculators

Nothing you type leaves your device No account Every formula shown

Start here
  1. Auto Loan Monthly payment, total interest, full amortization.
  2. Lease vs Buy Total cost of leasing vs financing the same car.
  3. Car Affordability How much car you can actually afford on your income.
  4. True Cost of Ownership Real $/year and $/mile after depreciation + everything.
Financing 14
Running Costs 6
The Car Itself 5
Financing

What the car really costs to borrow.

Loan payment, lease vs buy, what you can actually afford, and what extra payments save you.

All 14 in Financing
  1. 01

    Auto Loan

    Monthly payment, total interest, full amortization.
  2. 02

    Lease vs Buy

    Total cost of leasing vs financing the same car.
  3. 03

    Car Affordability

    How much car you can actually afford on your income.
  4. 04

    Auto Loan Early Payoff

    Interest saved and months cut by paying extra.
  5. 05

    Auto Loan Refinance

    Interest saved and months to break even on refi fees.
  6. 06

    0% APR vs Cash Rebate

    Which manufacturer promo actually costs less.
  7. 07

    Cash vs Finance

    Pay cash or take the loan — the honest break-even.
  8. 08

    Out-the-Door Price

    Sticker plus tax, doc fee, and registration — the real total.
  9. 09

    Upfit Cost

    What work equipment adds to the truck — and to the loan.
  10. 10

    Negative Equity

    How much underwater you are, and what rolling it costs.
  11. 11

    Lease Buyout

    Buy out at residual, or return — the equity decides.
  12. 12

    Early Lease Exit

    Leave mid-lease, or ride it out — payments count too.
  13. 13

    Lease Payment

    Monthly lease payment from cap cost, residual, money factor.
  14. 14

    Lease Mileage Overage

    Projected excess-mileage bill at lease-end.
Running Costs

What it costs to keep it on the road.

Fuel, charging, the full cost of ownership, and business-mile reimbursement.

All 6 in Running Costs
  1. 01

    Fuel Cost

    Cost per trip and per year at your MPG and gas price.
  2. 02

    EV Charging Cost

    Cost per charge, per mile, per year for an EV.
  3. 03

    True Cost of Ownership

    Real $/year and $/mile after depreciation + everything.
  4. 04

    Cost Per Mile

    All-in cost to drive one mile — fuel plus everything.
  5. 05

    MPG / Gas Mileage

    Real MPG from a tank, plus cost per mile and per year.
  6. 06

    Mileage Reimbursement

    Business-mile deduction at the current IRS rate.
The Car Itself

Depreciation, EV math, tires, towing.

What the car is worth over time, gas vs electric, and the physical-spec math most owners get wrong.

All 5 in The Car Itself
  1. 01

    Car Depreciation

    Projected resale value year by year.
  2. 02

    Gas vs Electric Total Cost

    Lifetime cost of an ICE car vs an equivalent EV.
  3. 03

    New vs Used Car

    Multi-year cost of buying new vs a used equivalent.
  4. 04

    Tire Size

    Dimension conversion + speedometer error.
  5. 05

    Towing Capacity & Payload

    Whether your setup is within safe tow + payload limits.
Read first · cornerstone guide
Financing ~12 min read

How auto loan interest actually works

A from-scratch derivation of the payment formula, what the dealer's monthly number hides, and the few levers that actually cut what a car loan costs. With the calculator inline.

Read the guide