Calculating Spend from Revenue and ROI I'm trying to figure out what the formula would be to generate the `Spend` if I know the `Revenue` and the `Return on Investment`. Here is the formula on how to calculate the ROI: (Revenue - Spend) / Spend And here is an example using the formula above: Spend: $100 Revenue: $300 Profit: $200 ROI: 200% So with the formula and example above, how do I generate `Spend` if I have the `Revenue` and `ROI`?

Let $S = Spend$

Let $R = Revenue$

Let $R_i = ROI$

You know $R_i = (R-S)/S$

Now, $SR_i = R-S$

$S(R_i+1) = R$

$S = \frac{R}{(1+R_i)}$