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Auto Loan Calculator – Real Monthly Payment Including Tax & Fees

Can you afford this car?

What This Does

An auto loan calculator sounds simple β€” enter the price, get a payment. But the number dealers quote you is almost never the number that matters. The sticker price doesn't include sales tax, dealer fees, or how your trade-in is actually applied. The monthly payment they show you doesn't tell you what the car actually costs. This calculator does both. Enter the vehicle price, your down payment, trade-in value, loan term, APR, sales tax rate, and fees. You'll see the real monthly payment, how much of each payment is interest, and the total cost of the vehicle over the life of the loan β€” not just the number you're handing over each month. The two numbers most people ignore are total interest paid and loan term length. A $35,000 car at 7.5% APR over 72 months costs $7,200 in interest. Shorten it to 48 months and that drops to $4,700 β€” a $2,500 difference for the same car. Knowing these numbers before you walk into a dealership changes the entire negotiation. Dealers focus on monthly payment precisely because it obscures the total cost.

Assumptions
  • Β·Sales tax is applied to the full vehicle price before subtracting trade-in value (varies by state β€” some states tax only the difference)
  • Β·Dealer fees and documentation fees are financed into the loan (most buyers do this)
  • Β·Assumes a fixed APR for the full loan term
  • Β·Trade-in value is applied as a direct credit against the purchase price
  • Β·Does not include gap insurance, extended warranties, or other dealer add-ons
How It's Calculated

Loan amount = (Vehicle price + sales tax + dealer fees) – down payment – trade-in value Monthly payment = Loan amount Γ— [r(1+r)^n] / [(1+r)^n – 1] Where: r = monthly interest rate (APR Γ· 12) Β· n = number of monthly payments (term in months). Total interest = (Monthly payment Γ— n) – Loan amount Example: $28,500 vehicle Β· 6.25% sales tax ($1,781) Β· $650 fees Β· $2,000 trade-in Β· $0 down Β· 60-month term Β· 7.9% APR β†’ Loan amount: $28,931 β†’ Monthly payment: $587 β†’ Total interest: $6,289 β†’ Total cost: $35,189.

When Should You Use This?
  • β†’Before visiting a dealership β€” know your real maximum monthly payment before they show you theirs
  • β†’Comparing 48 vs 60 vs 72-month terms β€” see how each changes total interest, not just payment
  • β†’Evaluating a trade-in offer β€” see whether rolling it in actually lowers your cost
  • β†’Shopping rates across lenders β€” plug in different APRs to see the dollar impact
  • β†’Deciding how much to put down β€” see how each extra $1,000 affects payment and total interest
Worked Examples

Example 1: Used SUV β€” comparing 60 vs 48 months

Inputs: Price: $28,500 Β· Trade-in: $2,000 Β· Tax: 6.25% Β· Fees: $650 Β· Down: $0 Β· APR: 7.9%

Result: 60 months: $587/mo Β· total interest $6,289 | 48 months: $717/mo Β· total interest $4,998 Β· savings: $1,291

The shorter term costs $130 more per month but saves $1,291 in total interest. If that payment fits your budget, the 48-month loan is the better financial decision by a significant margin.

Example 2: Impact of APR β€” dealer financing vs. credit union

Inputs: Price: $32,000 Β· Down: $3,200 Β· Tax: 7% Β· Fees: $600 Β· Term: 60 months

Result: Dealer at 8.9% APR: $614/mo Β· total interest $7,726 | Credit union at 6.5% APR: $577/mo Β· total interest $5,565 Β· savings: $2,161

Getting pre-approved at your credit union before visiting the dealer saves $37/month and $2,161 total. Pre-approval also gives you a rate benchmark to negotiate against the dealer's financing offer.

Auto Loan Calculator

Monthly Payment Β· Total Interest Β· Equity vs Depreciation Β· Rate Sensitivity

Results update in real time as you adjust any input.

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About This Calculator

This auto loan calculator computes monthly payment using the standard amortization formula P(r(1+r)^n)/((1+r)^n-1). Loan amount = vehicle price + sales tax + fees - down payment - trade-in. Full amortization schedule computed month-by-month with exact principal and interest splits. Depreciation estimate: 18% in year 1, 12%/year thereafter. Equity = estimated car value minus remaining loan balance. Underwater months counted until car value exceeds loan balance. Score (0-100): rate score (APR component) + term score (months component) + interest ratio score (total interest / loan amount) + affordability score (payment as % of income if provided). All 8 inputs update in real time.

The Breakdown tab renders a horizontal bar chart showing all cost components (principal, interest, down payment, tax, fees) with individual accent colours and LabelList right-side dollar values, plus a 3-line chart (car value, loan balance, equity) over the loan years showing the underwater crossover point. The Amortization tab renders a dual-area chart of monthly principal vs interest payments over the loan life (emerald area for principal building, red area for interest declining), plus the full month-by-month payment schedule table. The Scenarios tab renders a line chart of monthly payment across APR Β±3% (current rate marked with larger dot, LabelList dollar values) plus a bar chart of total interest at 5 loan terms (current highlighted, others faded red). The Insights tab shows 4 insights (payment details, equity timeline, rate impact, affordability or term trade-off) and 4 conditional What To Do Next steps based on loan quality score.

Results are estimates only and do not constitute financial, tax, or legal advice. Consult a qualified professional before making financial decisions.

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Common Mistakes to Avoid
  • βœ•Negotiating on monthly payment instead of purchase price β€” dealers can hide cost in a longer term or higher rate while keeping the payment the same
  • βœ•Not getting pre-approved before the dealership β€” walking in without a rate benchmark gives dealers pricing power
  • βœ•Overlooking total interest paid on long-term (72–84 month) loans β€” the payment looks manageable but the total cost is much higher
  • βœ•Accepting dealer add-ons (gap insurance, extended warranty) without pricing them independently β€” they're often 30–50% cheaper elsewhere
  • βœ•Trading in a vehicle without knowing its actual market value β€” check Carmax, KBB, and Carvana offers first
Frequently Asked Questions

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