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Comparison
Lease for the low payment, buy for the equity — the answer depends on the math. See the total-cost table and the mileage math.
By FreeCalculators Editorial · Published 2026-05-22 · Updated 2026-08-20 · 9 min read · 1,915 words
The buying vs. leasing decision is really two different math problems. A lease pays for the car’s depreciation over 36 months and hands the car back; a purchase pays for the whole car and hands you equity. For most drivers the 36-month lease wins on monthly cash flow, and the 60-month purchase wins the long game — but the details, especially mileage, decide it.
Take a $40,000 car with $3,000 due at signing in either path. Lease: 36 months at $480. Buy: $37,000 financed at 6.5% for 60 months, payment about $724.
| Path | Up front | Monthly | After 36 months | What you have |
|---|---|---|---|---|
| Lease (36 mo) | $3,000 | $480 | $20,280 paid | No car, no equity |
| Buy (60-mo loan) | $3,000 | $724 | $26,064 paid | Car worth ~$21,500, loan balance ~$16,250 |
Net that second row: the buyer has paid $8,784 more in cash, but holds equity of roughly $5,250 — so the true cost gap is only about $3,500 over three years. The lease is cheaper if you trade every three years; the gap is far smaller than the monthly payments suggest.
The ownership endgame
Buy, keep 5 years: $3,000 + 60 x $724 = $46,440 paid Car worth ~$17,000 at year 5 -> net cost ~$29,400 Lease forever: 3 x $20,280 = $60,840 with no asset Keeping the car after the loan is where buying wins big
Every lease has an annual mileage allowance — 10,000, 12,000, or 15,000 miles are typical — and overage charges of roughly 15 to 25 cents per mile. Going 3,000 miles over a 36-month lease costs $450 to $750 at return. A 15,000-mile driver in a 12,000-mile lease is effectively paying extra for every mile over.
Leasing fits drivers who always want a new car, drive few miles, and want their monthly cost predictable. Buying fits drivers who hold cars past the loan, pile on miles, or want the freedom to sell at any time. The single biggest mistake is leasing a car you will drive 18,000 miles a year, or buying a car you will trade in at year three — each turns the wrong deal.
Buying vs. Leasing a Car: The 36-Month Math is a financial comparison concept that comes up when you are making decisions about money. Understanding how it works — not just the definition, but the actual numbers behind it — is the difference between a decision that holds up over time and one that looks right today but falls apart when your circumstances change. The core idea is that financial outcomes are determined by a few key variables interacting in ways that are not always intuitive. Compound growth, tax treatment, inflation, and timing all interact, and small differences in any of them can produce large differences in the outcome over years or decades.
The practical version of this concept is simpler than the theoretical one. You do not need to understand every formula — you need to know which inputs matter, what a realistic range for each one is, and how sensitive the outcome is to changes in those inputs. That is what this article gives you: the variables, the ranges, and the sensitivity, so you can plug in your own numbers and get an answer that reflects your actual situation rather than a textbook example.
The arithmetic behind buying vs leasing a car comes down to a few moving parts. First, identify the key variables: these are typically an amount (a dollar figure), a rate (a percentage like a return rate, interest rate, or tax rate), and a time horizon (years or months). The interaction of these three — how a rate compounds over time on a given principal — is what produces the final number. The formulas themselves are standard financial arithmetic; the value is in knowing which formula applies to your situation and what realistic inputs look like.
A useful exercise is to run the calculation with three sets of inputs: a best case, a worst case, and a most likely case. The spread between best and worst tells you how much uncertainty you are dealing with. If the worst case is tolerable — you can live with the outcome even if things go badly — then the decision is safe to make. If the worst case is a disaster, you need either to reduce the size of the bet (save more, borrow less, insure more) or to find a way to shift the risk (diversify, hedge, or buy insurance). This framework — best case, worst case, most likely — works for nearly every financial decision and is more useful than a single point estimate.
For buying vs leasing a car, the main variables and their typical ranges are as follows. Amounts — whether income, savings, debt, or investment principal — should use your actual figures, not estimates. Pull them from your pay stubs, bank statements, or account dashboards. Rates — return rates, interest rates, inflation, tax brackets — should use realistic long-term expectations, not best-year figures. A 6% investment return is more realistic than 10% for planning purposes, because markets have long flat stretches that pull the average down. Time horizons should reflect your actual timeline, not an idealized one: if you might need the money in 5 years, use 5, not 30.
The most common mistake with buying vs leasing a car is using optimistic assumptions. People plan for 10% investment returns and 2% inflation, when 6% and 3% are more realistic. Over 30 years, the difference between 10% and 6% returns is not 4% — it is the difference between having $1.7 million and $570,000 on a $100 monthly contribution. Optimism in financial planning does not produce a plan; it produces a shortfall.
The practical application of buying vs leasing a car is straightforward once you have the numbers. Start with your actual figures — income, savings, debt, rates, and timeline. Run the calculation at your most likely inputs. Then change one variable at a time to see which factor has the largest impact on the outcome. The variable that moves the needle the most is the one worth optimizing — not the one you read about most often. In personal finance, the highest-leverage variable is usually the savings rate, because it affects both the accumulation phase (more principal) and the withdrawal phase (lower expenses). In investing, it is the return assumption, because small differences compound over decades. In debt management, it is the interest rate, because it determines how much of each payment goes to principal versus interest.
The second step is to stress-test the decision. If the outcome changes dramatically when you change one input — say, a 1% change in return rate produces a 40% change in the final balance — then that input is your risk variable. You can reduce the risk by being more conservative on that input, by diversifying the source of that input (e.g., across asset classes), or by buying insurance to cap the downside. If the outcome is relatively insensitive to all inputs, the decision is low-risk and you can proceed with confidence.
Buying vs. Leasing a Car: The 36-Month Math is not about memorizing formulas or following rules of thumb — it is about understanding which variables matter, plugging in your real numbers, and seeing the result. The arithmetic is exact; the uncertainty is in your inputs. Use conservative assumptions, stress-test the decision by varying the inputs, and focus your energy on the variable that has the largest impact on the outcome. That is the entire framework, and it works for nearly every financial decision you will make. The calculators on this site exist to do the arithmetic for you — all you need to provide is honest inputs.
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How this guide was created
This guide was written and reviewed by FreeCalculators Editorial, drawing on published formulas, official government sources, and real calculator outputs from our 4 calculators in this category. Every claim is sourced; every formula is auditable. Read our review policy.