How it works
It differs from POAS in its starting point: POAS shows how many times over the profit exceeds the spend, ROI shows what percentage above the money invested is left. ROI of 0% and POAS of 1 are the same state: breaking even.
Formula
(Profit − spend) ÷ spend × 100%
Example
The same shop: profit 63,000, spend 40,000.
ROI = (63,000 − 40,000) ÷ 40,000 × 100% = 57.5%.