The basic payback formula
Divide the total cost of the purchase by the net cash it produces each month. The result is the number of months to break even.
The formula is short:
Payback period (months) = total cost of the investment divided by monthly net cash gain.
Two details make or break the answer. First, use net cash gain, meaning extra profit after the direct costs of earning it, not extra revenue. Second, use the full cost, including installation, training, delivery, and the financing cost if you are borrowing.
Example (illustrative): a $24,000 commercial oven adds $2,000 a month in net profit. Payback is 24,000 divided by 2,000, or 12 months.
Worked examples for three common purchases
Different purchases pay back at different speeds. Calculate each with your own figures and compare them to the repayment term.
| Purchase | All-in cost | Monthly net gain | Payback |
|---|---|---|---|
| Delivery van for a bakery | $36,000 | $3,000 | 12 months |
| Inventory restock for a boutique | $15,000 | $2,500 | 6 months |
| Software and two hires for a design studio | $60,000 | $4,000 | 15 months |
The boutique recovers its money quickest because inventory turns over. The studio takes longest, because the benefit builds slowly as new clients arrive. Longer is not wrong, but it demands patience and a payment structure to match.
Match payback to the repayment term
The purchase should earn back its cost before or soon after the financing is repaid. A payback longer than the term strains your cash flow.
This comparison is the heart of the matter. If the oven pays back in 12 months and the funding is repaid over 18, the oven covers the payments with room to spare. If the funding is repaid over 6 months, you must find the rest of the money elsewhere for half a year.
- Payback shorter than term: the purchase funds its own payments.
- Payback about equal to term: tight, with no cushion.
- Payback longer than term: you cover the gap from other income.
This is why term loans and equipment financing suit assets with longer lives, and why shorter products suit inventory and quick-turn projects.
Include financing cost in the calculation
Add the interest and fees to the purchase cost before dividing. Otherwise the payback looks faster than it will be.
A $24,000 oven financed for a total repayment of $28,000 really costs $28,000 to own. At $2,000 a month in net gain, payback is 14 months, not 12. The two months are the price of borrowing.
Work out the full number first with our guide to the true cost of capital, then use it as the numerator. If you want a quick view of how payments compare with gains, put the monthly payment next to the monthly gain. When the gain is larger than the payment, the purchase is cash positive from the start. When it is smaller, you are subsidizing it.
Where payback period falls short
It ignores what happens after break-even and treats every month alike. Use it with total return and a downside check, not alone.
Payback is a speed test, not a profit test. Two purchases can both pay back in 12 months, yet one keeps producing for ten more years and the other wears out in two. Consider the life of the asset.
It also assumes the monthly gain is stable. A new location, a seasonal product or a campaign might ramp up slowly. Build a version with slower early months. Finally, it overlooks risk. A project with uncertain demand deserves a longer assumed payback than a machine that replaces a task you already pay for. See cost of capital versus ROI for a fuller view.
Choosing between two projects
Payback helps rank competing uses of the same dollars.
Suppose you can fund only one of two options (example only). A new refrigeration unit costs $18,000 and saves $1,500 a month in spoilage and energy, a payback of 12 months. A second storefront sign and local ad push costs $9,000 and adds $1,000 a month in profit, a payback of 9 months. The sign pays back faster, but the refrigeration unit keeps saving for years, and the sign's effect may fade.
Payback alone favors the sign. Combining it with asset life and risk may favor the refrigeration. Neither answer is automatic, which is why the number is a starting point for the decision and not the decision itself.
Stress-test your number
Cut the expected gain by 25 to 30 percent and recalculate. If payback still lands inside the term, the plan is sturdy.
Take the oven again. If the gain drops from $2,000 to $1,400 a month, payback becomes about 17 months on the cost alone. Does your cash flow handle that? If not, shrink the purchase, lengthen the term or wait.
Our equipment payback calculator post and the stress test guide walk through the process. ROI Funder is built around this arithmetic: you see the true cost, payback period and monthly-equivalent payment before you sign, with funding from $5,000 to $5,000,000 and a soft credit pull to apply.
Frequently asked questions
What is a good payback period?
It depends on the purchase and the repayment term. Inventory may pay back in months, equipment in a year or two. The key test is whether payback fits inside your term.
Should I use revenue or profit in the formula?
Use net profit or net cash gain. Revenue overstates the benefit because it ignores the direct costs of earning it.
Does payback period include interest?
It should when you are borrowing. Add the financing cost to the purchase price so the break-even month reflects what you actually pay.
Is payback period the same as ROI?
No. Payback measures time to recover cost. ROI measures total gain relative to cost. Use both to judge a project.