Key facts
- Net ROI = (contribution minus cost of capital) divided by amount invested.
- Inventory cost sits inside contribution margin; ad spend does not. Mixing them is the most common ROI mistake.
- A single inventory turn commonly returns 30% to 100% of its cost in contribution before capital costs.
- Cost of capital for an advance = amount times the flat fee; for borrowed money = amount times APR times weeks divided by 52.
Last updated September 7, 2026. Fee presets, payout timing, and Onramp Funds eligibility and fee example checked against the published sources listed at the end of this page.
How to use the ROI calculator
Enter the amount invested, the revenue it produces, your contribution margin, and how many weeks it takes. Tell the calculator whether the money bought inventory (its cost is already inside the margin) or advertising and launch spend (on top of margin), and how it was funded: your own cash, an advance with a flat fee, or a loan or card at an APR. The result is net ROI after the cost of capital, the return per dollar, the break-even revenue, and the payback period on a cash timeline.
The formulas
Contribution = revenue × contribution margin. Gross return = contribution, minus the spend when the spend is advertising. Cost of capital = amount × flat fee for an advance, or amount × APR × weeks ÷ 52 for borrowed money. Net return = gross return minus cost of capital. Net ROI = net return ÷ amount invested. Payback period = amount invested ÷ weekly contribution.
What makes this different
- Cost of capital is inside the answer: most ROI calculators stop at gross return. This one asks how the investment was paid for and takes the cost off the top, which is the comparison that decides whether to borrow for it.
- Inventory and ads handled correctly: inventory cost sits inside contribution margin; ad spend does not. Mixing them is the most common ROI mistake.
- Cash timeline on every result: when the money goes out, when it comes back, and the lowest point in between.
- Compare two scenarios side by side, share a link with your numbers, or save the result as a PDF. Inputs carry over between the calculators on this site.
- Nothing is stored. Everything runs in your browser.
ROI versus cost of capital is the whole decision
An inventory turn that returns 60% gross funded by an advance with a 10% flat fee nets 50%. The same turn skipped for lack of cash nets nothing. That is the calculation behind revenue-based financing: a flat fee against a known return, repaid as a percentage of the sales the investment creates. Onramp Funds advances capital against combined sales, with no personal credit check. See how much capital your combined revenue unlocks.
Sources
Frequently asked questions
What is a good ROI for ecommerce inventory?
A single inventory turn commonly returns 30% to 100% of its cost in contribution before capital costs, depending on margin and sell-through speed. Faster turns compound the annualized figure.
Should I annualize ROI?
Annualized ROI is useful for comparing investments of different lengths, but the per-cycle figure is what tells you whether a specific order or campaign was worth funding.
Does this calculator store my data?
No. Everything runs in your browser and nothing is uploaded.
Onramp Funds
Funding built around your sales
Connect your store and see what you qualify for. Repay as a percentage of sales, with no personal credit check.
Funding in as little as 24 hours.
