Your car

The first slider sets the price of the car you’re considering, followed by your down payment, APR, and loan term. The estimated payment updates immediately below. A $42,000 car with $6,000 down at 7.5% APR over 60 months comes out to roughly $721 a month, and that monthly figure is what feeds every result on this page.

Compare it with

Choose what you’re weighing this purchase against: paying cash for the exact same car, or buying a cheaper one instead and pocketing the difference. The two comparisons produce different math. Paying cash for the same car mostly isolates the cost of financing itself, since the car’s resale value is identical either way. Buying a cheaper car brings a second car’s resale value into the picture, because you’d be giving up a different asset, not just a different loan. The cheaper-car slider can’t go above your chosen car’s price, so the comparison always stays a meaningful downgrade.

Your retirement

Your current age and target retirement age set the time horizon everything else compounds over, and the target age slider can’t drop to or below your current age. Assumed annual return is capped between 3% and 10% on purpose, so an unrealistic number can’t manufacture a dramatic result. Your current monthly retirement contribution is only used if this car does create a gap — it determines how many extra years of contributing at that same rate it would take to close it.

Freed-up money you would invest

Choosing the cheaper path changes your cash flow in two places: you pay the cheaper car’s full price upfront instead of just a down payment, and you avoid the monthly loan payment entirely afterward. Depending on your down payment and the cheaper car’s price, that upfront difference can run either way — more cash today, less, or about the same. Most people don’t route every freed-up dollar into an investment account the moment it’s available — some of it gets absorbed into ordinary spending instead. This slider applies one realistic share to the whole difference between the two paths, upfront and monthly combined, so it stays simple to reason about instead of asking you to guess two separate behaviors. At 0%, only the resale-value difference between the two paths affects your result. At 100%, the entire difference is treated as if it were invested in full.

Resale value assumptions

Both resale fields start with a simple illustrative depreciation estimate based on the car’s price and loan term — actual resale values vary substantially by make, model, mileage, condition, and market, so overwrite either field if you know the car’s specific expected trade-in value. This is where the depreciation math lives on this page: it only affects your result when you’re comparing two different cars, because two paths to the same car depreciate identically and cancel out on their own.

Retirement impact

This is the main result. It converts the projected wealth gap between your two paths into a number of years — specifically, how many additional years of continuing your current contribution rate it would take to close that gap, which is a close but not identical stand-in for a literal retirement-date shift. The line underneath the number spells this out and shows the assumptions used, so the figure doesn’t read as more certain than it is. The horizontal line below shows your current age, your target retirement age, and, if the numbers work out that way, how far right that target moves.

Retirement-safe car price

This works backward from your own numbers to answer a different question: given everything else you’ve entered, what’s the most expensive car you could buy today without moving your retirement date at all? It updates as you adjust every other slider on the page, including your target age and your assumed return — but not your monthly retirement contribution, which only changes how fast an existing gap could be recovered, not whether one exists in the first place. The short note underneath the price spells that out directly, and if your inputs push the answer past the edges of what this tool checks, it says so rather than showing a number that looks more exact than it is.