★ COMPARISON · MONEY · CAR BUYING
Paying cash feels safe and financing feels clever — this calculator settles it with arithmetic instead of gut feeling. At the defaults — a $30,000 car, $5,000 down, 6.9% APR over 60 months, and a 7% assumed return — the monthly payment is $493.85, financing costs $4,631.08 in interest, investing the $25,000 loan amount would gain $10,440.63, and financing wins by a net $5,809.55. Change any number and the verdict updates: the winner depends entirely on your APR, your term, and whether the money really stays invested.
Enter the car price, down payment, loan APR and term, and the annual return you assume the financed money would earn if invested instead. The model is stated exactly below the calculator: the finance buyer invests the full loan amount as a lump sum, monthly-compounded, for the whole loan term. That assumption is the whole argument — if the money gets spent, the financing case collapses.
Car price P, down payment D, loan amount L = P − D at APR r over N months. Monthly interest rate i = r ÷ 12. Monthly payment = L · i ÷ (1 − (1 + i)−N), or L ÷ N when APR is 0%. Finance total outlay = D + N · payment. Interest paid = finance total outlay − P. Opportunity leg: the finance buyer invests L as a lump sum at assumed annual return R, monthly-compounded, for N months, so investment gain = L · ((1 + R ÷ 12)N − 1). Net finance advantage = investment gain − interest paid. Positive means financing wins; negative means cash wins.
Setup: P = $30,000, D = $5,000, so L = $25,000; APR 6.9%, so i = 0.069 ÷ 12 = 0.00575; N = 60; R = 7%.
Line 1 — the payment. 25,000 × 0.00575 ÷ (1 − 1.00575−60) = $493.85 per month.
Line 2 — the finance total. $5,000 + 60 × $493.85 = $34,631.08, so interest paid = $34,631.08 − $30,000 = $4,631.08.
Line 3 — the investment gain. $25,000 × ((1 + 0.07 ÷ 12)60 − 1) = $10,440.63; the invested pot ends at $35,440.63.
Line 4 — the verdict. $10,440.63 − $4,631.08 = +$5,809.55: positive, so financing wins at the defaults — by a margin that depends entirely on that 7% return actually happening.
At 0% APR the payment is simply $25,000 ÷ 60 = $416.67, the finance total is exactly $30,000, interest is $0, and the net financing advantage is the full investment gain: +$10,440.63. A true 0% loan is free money only if you forgo no cash rebate to get it — compare the out-the-door price with and without the promotional rate before celebrating.
At 12% APR the payment jumps to $556.11, the finance total reaches $38,366.67, and interest paid is $8,366.67. The investment gain is unchanged at $10,440.63, so the net financing advantage shrinks to +$2,073.96. Financing still wins on paper, but the margin is now thin enough that one bad investment year erases it — at 12%, cash deserves a serious look.
Over 36 months the payment rises to $770.78, but the finance total falls to $32,748.26 and interest to $2,748.26. The investment only compounds for three years, gaining $5,823.14, so the net financing advantage is +$3,074.88 — smaller than the 60-month case, because less time means less compounding on both sides of the ledger.
Keep the 6.9% loan but assume only a 4% return, and the investment gain falls to $5,524.91 against the same $4,631.08 of interest. The net financing advantage is just +$893.84 — barely positive. This is the honest version of the financing argument: at a bond-like return, financing a 6.9% loan is nearly a coin flip, and the peace of mind from owning outright may be worth more than $894 spread over five years.
With no down payment, L = $30,000, the payment is $592.62, the finance total is $35,557.29, interest is $5,557.29, and the investment gain on the larger lump sum is $12,528.76. Net financing advantage: +$6,971.46. Financing more money magnifies both sides — and leaves you owing the full price on a depreciating asset from day one.
| Output | Formula | What it means |
|---|---|---|
| Monthly payment | L · i ÷ (1 − (1 + i)−N) | $493.85 at the defaults — what leaves your account every month for 60 months. |
| Interest paid | D + N · payment − P | $4,631.08 at the defaults — the price of borrowing, on top of the car itself. |
| Investment gain | L · ((1 + R ÷ 12)N − 1) | $10,440.63 at the defaults — what the loan amount earns if it truly stays invested. |
| Net finance advantage | gain − interest | +$5,809.55 at the defaults — positive means financing wins, negative means cash wins. |
The arithmetic is exact for the inputs, but the model is deliberately simple: it ignores sales tax, dealer fees, insurance differences (lenders usually require full coverage), the cash rebate sometimes lost with promotional APRs, and the fact that investment returns are volatile, taxed, and never guaranteed — a 7% average over five years can still include a year that ends underwater. It also assumes the finance buyer invests the entire loan amount on day one and never touches it, which is the behavior the financing case needs and the behavior most people do not manage. Error policy: a non-positive price, a down payment at or above the price, negative rates, or a zero or negative term are reported as errors rather than modeled.
Bright Side Kit. "Cash vs Finance a Car Calculator." https://brightoolbox.com/cash-vs-finance-car/ Accessed October 24, 2026.Data sourcesIt depends on your APR and on what the money would otherwise earn. At the defaults here (6.9% APR, 7% assumed return), financing wins by $5,809.55 — but at a 4% return the margin collapses to $893.84, and at a high APR it can vanish entirely. Run your actual numbers; there is no universal answer.
You pay a down payment plus monthly payments, and you compare that against investing the loan amount. Loan amount = price minus down payment; the payment follows the standard amortization formula; interest is the finance total minus the price; and the investment gain is what the loan amount earns, monthly-compounded, over the term.
Not always. At a true 0% APR this calculator shows $0 interest and a $10,440.63 financing advantage at the defaults — but promotional rates sometimes replace a cash rebate, so compare the out-the-door price of the 0% deal against the cash price before you decide.
No — it lowers the payment and raises total interest. The 60-month default costs $4,631.08 in interest, while the 36-month branch costs only $2,748.26, even though its $770.78 payment is much higher. A longer term also stretches the investment window, which is why the 60-month net advantage ($5,809.55) beats the 36-month one ($3,074.88) at a 7% return.
Then the financing case in this calculator does not apply to you. Without the $10,440.63 investment gain, financing at the defaults costs $4,631.08 in interest for nothing, and cash wins outright. Be honest about this before trusting a “financing wins” verdict.
Sales tax, dealer fees, insurance requirements, rebates, and investment taxes and volatility. Lenders usually require full coverage insurance, which can cost more than a cash buyer's liability-only policy, and investment returns are never guaranteed. Treat the verdict as a starting point, not a final answer.
Usually not, even though the math can look generous. At $0 down the net financing advantage is $6,971.46 at the defaults, but you owe the full $30,000 on an asset that loses value immediately, and a larger loan means a larger payment ($592.62) every month. A down payment also protects you if the car is totaled early.