1. Track Conversions: Track the number of conversions (sales, leads, sign-ups, etc.) that you receive from your SEM campaigns.
2. Calculate Cost per Conversion: Divide the total cost of your SEM campaign by the number of conversions you received.
3. Calculate Revenue per Conversion: Divide the total revenue generated from your SEM campaign by the number of conversions you received.
4. Calculate Return on Investment (ROI): Subtract the cost per conversion from the revenue per conversion to calculate your return on investment (ROI).