Lease vs Buy: The Honest Math the Payment Comparison Hides

Ask the internet “should I lease or buy?” and you get a tribal answer. Lease people cite the lower payment and the always-new car. Buy people cite “you own nothing at the end.” Both are arguing from a payment or a slogan, and both are skipping the only comparison that means anything: what each path costs over the full stretch of years you’ll actually be driving.

This post builds that comparison from scratch. We’ll derive how a lease payment is constructed (it is not mysterious), show precisely why the lease-payment-vs-loan-payment comparison is rigged in the lease’s favor, and reduce the real decision to four numbers. There’s a calculator embedded below to run your own.

Why the payment comparison is rigged

A lease payment is almost always lower than a loan payment on the same car. This is presented as evidence that leasing is cheaper. It is not evidence of anything, because the two payments buy completely different things.

When you finance a purchase, your payment buys the entire car — all of its value, including the 40-60% of value it will still have years later. When you lease, your payment only buys the slice of value the car loses during the lease plus a finance charge. Of course the lease payment is lower. You’re financing a fraction of the asset. Comparing the two payments is like comparing the rent on an apartment to the mortgage on a house and concluding renting is cheaper because the monthly number is smaller. The monthly number being smaller is the definition of renting, not a discovery about cost.

The honest question is not “which payment is lower.” It is: over the N years I will keep driving, what is the total cash out the door, net of anything I still own at the end? Answering it requires putting both paths on the same timeline and counting three things the payment comparison omits — which we’ll get to after the lease math.

How a lease payment is actually built

A lease payment has exactly two components, and once you see them the whole thing is demystified.

The depreciation fee. You pay for the value the car loses while you have it. If the adjusted capitalized cost (roughly, the negotiated price minus any cap-cost reduction) is C and the residual value at lease end is R, then over a lease of n months you owe:

depreciation fee = (C − R) / n

That’s it for the first half — the car’s value drop, spread evenly across the lease.

The finance charge (rent charge). You’re using the leasing company’s capital, so you pay for it. Leasing expresses its interest rate as a money factor, a small decimal that obscures the real rate. The relationship is:

money factor = APR / 2400      (so 0.0025 ≈ 6% APR)
finance charge = (C + R) × money factor

The (C + R) looks odd — why add the residual to the cap cost? Because the finance charge is mathematically equivalent to charging interest on the average capital outstanding over the lease, and the average of a balance that declines from roughly C to R is proportional to (C + R). The money factor already has the factor-of-two baked in, which is why the APR conversion divides by 2400 rather than 1200.

The monthly lease payment is the sum, usually with sales tax applied on top in most states:

lease payment = (depreciation fee + finance charge) × (1 + tax rate)

The first practical takeaway: always convert the money factor to an APR (multiply by 2400) and compare it to a loan rate. A marked-up money factor is a hidden rate hike, and it’s hidden specifically because it’s quoted as “0.00275” instead of “6.6%.”

The three things the payment comparison omits

Put both paths on a fixed ownership horizon — say, the realistic six or eight years you keep a car — and three costs the payment comparison ignores snap into view.

1. The buyer ends up owning an asset. At the end of the horizon the person who bought has a car worth its resale value — real money, recoverable by selling. The person who leased has nothing; the residual equity belonged to the leasing company. This is the single biggest factor and the one the lease payment is structured to make you forget.

2. A short lease is re-signed, and drive-off cash recurs. A three-year lease over a six-year horizon is signed twice. Every signing brings a cap-cost reduction, an acquisition fee, and a disposition fee at turn-in. That drive-off cash is pure friction and it recurs every cycle. Buying-and-keeping incurs it once.

3. There are no payment-free years in a lease. A bought car gets paid off. Every month after payoff that you keep driving a still-valuable car is essentially free transportation. A lease never reaches that state — you are always making a payment, forever, by design. The longer your real ownership horizon, the more decisively this favors buying.

Leasing always wins the monthly-payment comparison. It usually loses the one that counts: total cost over the years you actually keep driving.

Run it on your own numbers

The calculator below levels both paths onto one horizon. It builds the lease payment from the residual and money factor, totals every drive-off across however many leases the horizon needs, amortizes the purchase loan, credits the buyer with the car’s resale value at the end, and charges each side the opportunity cost of the cash it ties up.

Try this: set a realistic long horizon (eight years if that’s how long you keep cars). Watch buying pull ahead as the horizon lengthens — that’s the payment-free years and the retained asset compounding. Then shorten the horizon to three years and watch leasing close the gap or win — over a single short cycle, with no payment-free period for either side, the lease’s lower outlay is competitive.

The fourth number: opportunity cost

There’s a subtle cost on both sides that a fair comparison must include: the cash you put down isn’t free even when it’s “only” a down payment or a cap-cost reduction. That money, invested instead, would have earned a return over the horizon. A rigorous comparison charges each side the foregone return on the cash it ties up. The calculator does this symmetrically — it’s why a large purchase down payment isn’t automatically “better”; beyond the point of avoiding negative equity, that cash often works harder invested than sunk into a depreciating asset.

This is also the strongest legitimate financial argument for leasing: it ties up less of your capital. If you genuinely invest the difference, that has real value. The catch is the word “genuinely” — the argument only holds if the freed cash is actually invested, not spent on a nicer car.

What actually decides it: four numbers

Strip away the tribalism and lease-vs-buy comes down to four inputs, all of which the calculator exposes:

1. Your real ownership horizon. Not how long you think — how long you actually keep cars. Long horizons favor buying, hard. Short horizons narrow or reverse it.
2. How fast the specific car depreciates. Leasing wins on fast-depreciating cars (you offload the depreciation risk onto the leasing company). It loses on strong-resale cars (you’d have kept that value).
3. The money factor versus a loan rate. Convert it. A marked-up money factor can quietly make leasing the more expensive financing even before the asset argument.
4. What your cash earns elsewhere. If freed capital genuinely compounds at a high return, leasing’s lower capital lock-up is worth real money. If it doesn’t, that argument evaporates.

Notice that none of these four is “the monthly payment.” That number isn’t on the list because it doesn’t belong in the decision — it’s the variable the comparison is rigged around, not an input to a sound choice.

When leasing genuinely wins

To be fair to leasing, here is when the honest math actually favors it:

• You truly keep cars only 2-3 years. No payment-free years are being given up because you’d never have reached them anyway.
• The car depreciates fast. Luxury sedans, many EVs, anything with steep year-one drops — leasing hands that loss to someone else.
• You’d otherwise tie up a large down payment that you will genuinely invest. The capital efficiency is real if the discipline is real.
• You value always being under warranty and never dealing with resale, and you’re willing to pay a modest premium for that convenience. That’s a legitimate preference — just price it honestly rather than pretending it’s the cheaper option.

What does not make leasing cheaper: the lower monthly payment, the new-car feeling, or “you own nothing at the end” used as a slogan in either direction.

What the model deliberately ignores

The calculator’s comparison is honest about its boundaries. It does not model:

• Mileage overage and wear charges. Leases cap miles and bill for excess and damage at turn-in. Heavy drivers pay materially more than the base math shows — a real and often decisive cost against leasing for high-mileage drivers.
• Maintenance divergence. A leased car is usually under warranty the whole term; a kept car incurs out-of-warranty repairs in later years. The True Cost of Ownership calculator covers that side.
• The lease buyout option. The model assumes you re-lease, not buy the car at its residual. A buyout below market can change the math.
• Business tax treatment. Lease and purchase are deducted differently for business use; that’s a tax-advisor question, not a calculator one.

As always, a trustworthy model isn’t one that captures everything — it’s one whose omissions are stated so you know when to look past it.

The one-paragraph version

A lease payment is lower than a loan payment because it only finances the slice of value the car loses during the lease, not the whole car — comparing the two payments is comparing rent to a mortgage. The honest comparison puts both on your real ownership horizon and counts the retained asset the buyer keeps, the recurring drive-off cash a re-signed lease incurs, the payment-free years a bought car eventually gives, and the opportunity cost of tied-up capital on both sides. Four numbers decide it: your true horizon, the car’s depreciation, the money factor converted to an APR, and what your cash earns elsewhere. Run your specific case through the lease vs buy calculator before you let anyone show you a monthly payment.

Related calculators

• Lease vs Buy Calculator — both paths on one horizon, net of resale and opportunity cost.
• Auto Loan Calculator — the purchase-side payment and total interest in detail.
• Car Depreciation — project the resale value the comparison hinges on.
• True Cost of Ownership — fuel, insurance, and maintenance on top of the financing choice.

AutoMath is an educational tool, not financial advice. Money factors, residuals, and tax treatment vary by vehicle, region, and time — confirm lease terms with the dealer before signing.