● Opportunity cost analysis

Cash vs Installments Calculator

Is it smarter to pay cash upfront or finance and keep your money invested? This calculator compares the true cost of both options.

Finance when the loan's effective annual rate is below the return you would earn on the cash you keep invested; pay cash when it is above. A cash discount tilts the answer toward cash, because a discount is an immediate, certain saving while an investment return is only expected. This calculator settles it in dollars: it carries both options to the same future date and shows which one leaves you with more.

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Purchase price · Finance rate · Investment return · Term

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Your scenario

Purchase price

Financing interest rate (APR)

Loan term

months

Investment return on cash (if you keep it invested)

% /yr

Cash discount offered (if any)

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True cost comparison

Pay cash

Cash paid upfront

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Investment gains foregone

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True cost of paying cash

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Finance (installments)

Monthly payment

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Total interest paid

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Total paid in installments

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True cost of financing

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How it's calculated

Opportunity cost: the key to the cash vs finance decision

The mistake that makes this decision hard is adding up money that leaves your pocket on different dates. Paying cash is one outflow today; paying in installments is a stream of outflows spread over months. A dollar you still hold next year is worth more than a dollar you hand over today, because it can earn a return in the meantime. So before anything can be compared, both options have to be moved to the same moment in time — here, the end of the term.

Both options are brought to the same moment: the end of the term. Pay cash — the money leaves today, so carry it forward = Price × (1 − discount%) × (1 + invest_rate)^years Finance — each installment leaves in a different month, so carry each one forward Monthly payment = P × r(1+r)^n / [(1+r)^n − 1] True cost = payment × [(1+i)^n − 1] / i, with i = (1+invest_rate)^(1/12) − 1 The smaller future value is the cheaper option. Comparing the APR with the investment rate is not enough: the loan charges interest on a balance that shrinks every month, while your cash would compound on the full amount.

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Cash price (after discount)
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Monthly installment
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Total paid in installments
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4
Installment interest cost
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Opportunity cost: The return you forgo by using cash for a purchase instead of investing it. At 7%/yr, $10,000 grows to $11,449 in 2 years — that's the opportunity cost of paying cash.
APR (Annual Percentage Rate): The true annual cost of financing including all interest. Compare directly to your investment return rate.

🔢 Worked example 1 — 0% financing, so financing wins

$12,000, 0% over 12 months ($1,000 a month), cash invested at 6% a year.
Pay cash: $12,000 × 1.06 = $12,720 at the end of the year.
Finance: monthly equivalent of 6% is i = 1.06^1/12 − 1 = 0.4868%. Carrying twelve $1,000 payments forward gives 1,000 × [(1.004868)¹² − 1] ÷ 0.004868 = $12,326.53.
Financing wins by $393.47 — the money you did not hand over kept earning while the loan charged nothing.

🔢 Worked example 2 — a 10% APR loan, so cash wins

$10,000 at 10% APR over 24 months, cash invested at 4% a year.
Monthly payment = 10,000 × 0.008333 ÷ [1 − 1.008333⁻²⁴] = $461.45; total paid $11,074.78, of which $1,074.78 is interest.
Pay cash: $10,000 × 1.04² = $10,816.00. Finance, carrying each payment forward at 4%/yr: $11,501.91.
Paying cash wins by $685.91 — the loan's effective annual rate (10.47%) is far above the 4% the cash could earn.

Disclaimer: this analysis ignores taxes (investment gains may be taxable; mortgage interest may be deductible), psychological factors (debt aversion), and liquidity needs. Use as a starting point, not a final decision. Always confirm with an official source before deciding.

Frequently asked questions

Should I pay cash or pay in installments?

Compare the loan's effective annual rate with the return you would earn on the money you keep invested. If the return is higher, financing leaves you better off; if the loan rate is higher, pay cash. A cash discount tilts the answer toward cash, because a discount is an immediate, guaranteed saving while an investment return is neither.

How do you compare cash and installments fairly?

You cannot add up money that leaves your pocket on different dates. Both options must be carried to the same moment — here, the end of the term. Cash: price × (1 + investment rate)^years. Installments: each payment carried forward, payment × [(1 + i)^n − 1] ÷ i, with i the monthly equivalent of your investment rate. The smaller total is the cheaper option.

Is 0% financing always better than paying cash?

Almost always, if you genuinely invest the cash. Example: $12,000 at 0% over 12 months while the cash earns 6% a year. Paying cash costs $12,720 by the end of the year, financing costs $12,326.53 — financing wins by $393.47. The exception is a cash discount available only to cash buyers, which can be worth more than a year of returns.

How much is a cash discount actually worth?

A discount is an immediate, risk-free return on the full amount. A 5% discount on a $10,000 purchase saves $500 the moment you buy — a certain 5%, whereas an investment return of 5% is only expected and can turn out lower. Enter the discount and the calculator applies it to the cash side before comparing.

Why isn't comparing the APR with my investment return enough?

Because the two rates apply to different amounts. The loan charges interest on a balance that shrinks with every payment, while your cash would compound on the full amount the whole time. That is why financing can win even when the APR looks close to your investment return — and why the comparison has to be made in currency, at the same date, not in percentages.

Are my results saved? Do I need an account?

No account or sign-up needed. Every calculation is saved automatically in your own browser, and you can also pin a result with the save button. Nothing is sent to any server: the data stays on your device and can be erased at any time with the clear button.

How do I track my progress over time?

From the fourth entry onward a “View comparison chart” button appears, opening a line chart with every entry in time order plus an indicator panel: total change, average per entry, lowest and highest value and the period covered. You can also export the history as CSV.

About this calculator

The cash vs. installments calculator helps you decide whether paying upfront or splitting a purchase into monthly payments is the better deal. You enter the cash price, the installment plan and the return you could earn on the money if you kept it invested, and it compares the true cost of each option.

Even an interest-free installment plan is not always free: money kept in your pocket can be invested and earn a return, while a cash discount is a guaranteed saving. The tool weighs these effects so you can see which choice actually leaves you better off.

Related calculators

Loan amortization — the full payment schedule behind the installment plan, month by month.
Car loan — the same decision for the purchase where it comes up most often.
Rate converter — turn the quoted APR into the effective annual rate you actually compare against your return.
Real return — check what your investment return is worth once inflation is taken out.
Compare investments — decide where the cash you keep would actually go.
Credit card payoff — if the installments are on a card, the interest is usually far above any return.

By Vinicius Fonseca · Reviewed against official sources · Updated Aug 2026 · How we calculate →