Budget-first beats payment-first
Dealers sell payments, and any payment can be manufactured with a long enough term — that's how buyers end up in 84-month loans on depreciating assets. Working budget-first with a sane term (48–60 months) fixes the decision before the showroom: you know your ceiling, and the sensitivity table shows exactly what another $100/month buys. When you've picked a target car, price the full deal — trade-in payoff, state tax rules, fees — in the auto loan calculator, and read how car loan interest works for the term-length math.
How this calculator works
Instead of price to payment, this tool solves the inverse problem — payment budget to price ceiling:
Loan your budget supports
P = M × ((1 + r)ⁿ − 1) ÷ (r(1 + r)ⁿ)
Price ceiling
price = P + down + trade-in, net of your state’s tax and fees
- M — your monthly payment budget
- r — monthly rate — APR ÷ 12
- n — loan term in months
Because sales tax scales with the very price being solved for, the engine bisection-searches the price until the resulting payment lands exactly on your budget — your state’s tax rule (trade-in credit or not) included.
Worked example
A $500/month payment budget with $3,000 down and no trade-in, at 7% in a 6% sales-tax state, comparing a 60-month and a 48-month loan.
| Max price at 60 months | $28,251 |
|---|---|
| Loan at 60 months | $25,251 |
| Max price at 48 months | $23,880 |
| Cost of the shorter term | ~$4,400 less car |
The same $500 budget buys a $28,251 car at 60 months but only $23,880 at 48 months — the longer term stretches your dollar but keeps you paying (and at risk of going underwater) longer. Budget-first beats payment-first: solving for the price your payment supports, tax included, keeps showroom gravity from pulling you into a bigger loan. Pair it with the 20/4/10 rule for a sanity check.
Frequently asked questions
How much car can I afford on my salary?
The 20/4/10 guideline: 20% down, finance no more than 4 years, and keep TOTAL car costs (payment + insurance + fuel) under 10% of gross monthly income. On an $80,000 salary that’s roughly $660/month all-in — meaning a loan payment nearer $400–450. Enter your payment budget above and the calculator converts it to a sticker price.
How does the calculator turn a budget into a price?
It inverts the loan math: your budget defines the maximum loan at your APR and term; then it adds your down payment and trade-in and backs out sales tax (respecting whether your state taxes the price before or after trade-in credit) to find the price whose payment exactly equals your budget.
Why does the max price drop if I roll tax into the loan?
Financed tax consumes loan capacity: every borrowed tax dollar is a dollar of car you can’t finance. We assume tax paid upfront for the max-price math; the full auto loan calculator models both ways.
Should I count insurance in the budget?
Yes — outside the loan. Insurance runs $100–$250+/month depending on driver and vehicle, and sporty or new models cost more to insure. A $450 loan budget with $180 insurance is really a $630/month decision; the 10% rule is about the total.
New or used for a tight budget?
Used generally wins on price and depreciation, but carries higher APRs (typically +1–3 points) and maintenance risk. Try the calculator both ways: same budget, used APR vs new APR — the price gap narrows more than people expect, but rarely closes.
How much should I put down on a car?
20% on new (roughly matching first-year depreciation, keeping you above water) and ~10% on used is the classic guidance. Less down is common but raises the odds of owing more than the car’s worth — the negative-equity trap covered in our car loan guide.
Related calculators
- Auto Loan Calculator — Estimate car payments including trade-in value and state sales tax.
- Auto Refinance Calculator — Check the refi math on your car loan in 30 seconds — fees included, longer-term trap flagged.
- Loan Payoff Calculator — See how extra payments shorten your loan and how much interest you save.
- Home Affordability Calculator — How much house can you afford? Income, debts, and the 28/36 rule turned into a real price range.
Disclaimer: Educational purposes only — not financial advice. Insurance, fuel, and maintenance are outside the loan math — budget them separately. See our Terms of Use.