AI Agent ROI: How to Calculate It (Method + Worked Example)
The simple formula to estimate the return on an AI project, a concrete example for a 10-person SMB, and the hidden costs you shouldn't forget.
Why calculate ROI before you start
85% of French companies increased their AI investments in 2025 (Deloitte). But 40% underestimate hidden costs. Calculating the return before you sign is the difference between a profitable project and a disappointing expense.
The simple ROI formula
ROI (%) = (Annual gains − Total cost) ÷ Total cost × 100
And its essential companion, the payback period:
Payback (months) = Investment ÷ Monthly gain