Finance · 7 min read · Free
How to Calculate ROI on a Resale Deal
Profit tells you how many dollars you made. ROI tells you what those dollars produced relative to the capital you put at risk.
Return on investment gives resellers another way to compare deals. A $150 profit on a $500 purchase and a $150 profit on a $1,500 purchase are not economically identical. ROI helps show how efficiently your buying capital produced profit, while days to sell tells you how long that capital was unavailable. The best decision is not always the deal with the highest dollar profit or the highest percentage alone. You need to understand return, time, risk, and repeatability together.
What it is
ROI measures profit relative to the capital invested in a deal. A simple reseller formula is ROI = realized profit ÷ acquisition cost × 100. It helps compare how efficiently different purchases used your buying capital.
Why it matters
Dollar profit alone can hide capital efficiency. Making $150 on a $500 purchase is different from making $150 on a $1,500 purchase. ROI becomes even more useful when paired with days to sell because capital can be recycled multiple times when inventory turns quickly.
When to use it
Use ROI when comparing products with different purchase prices, evaluating whether a larger deal is worth tying up more cash, reviewing sourcing channels, or deciding which categories deserve a larger inventory budget.
How to do it
First calculate realized profit consistently. Then divide that profit by the capital invested in the item. Use the same definition of invested capital every time; acquisition cost is a practical starting point, and you can include landed costs if that is how you manage purchasing. Next record days to sell. Do not automatically choose the highest ROI: consider risk, defect rate, effort, repeatability, and whether enough similar opportunities exist.
Worked example
Deal A costs $500 and earns $150 after direct costs. ROI is 30%. Deal B costs $1,500 and also earns $150. ROI is 10%. If Deal A sells in 10 days and Deal B sells in 40 days, Deal A used less capital and returned it faster. That does not prove Deal A is always superior—perhaps Deal B is dramatically safer or available in much higher volume—but it reveals a difference that dollar profit alone hides.
Your action plan
- Calculate realized profit for each completed sale.
- Divide profit by the invested acquisition cost and convert it to a percentage.
- Record days from purchase to sale.
- Compare ROI, dollar profit, days to sell, return rate, and effort together.
- Look for repeatable deal types rather than one unusually good transaction.
Common mistakes
- Comparing ROI using inconsistent cost definitions.
- Ignoring how long the capital was tied up.
- Choosing a very high ROI on tiny deals without considering time required.
- Ignoring returns, defects, or sourcing difficulty.
- Treating historical ROI as a guaranteed future return.
Key takeaway
ROI tells you how hard your capital worked. Days to sell tells you how long it had to work.
Try this
Calculate ROI and days-to-sell for five completed deals and compare them with the dollar profit you normally look at.
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