Calculate your revenue:
Your revenue is your conversions multiplied by your average revenue per conversion. For instance, 30 conversions x $50 per conversion = a total revenue of $1500.
Calculate your costs:
Your costs are your Google Ads cost (budget) + your business overhead. For instance, $300 budget + $1125 overhead = a total cost of $1425.
Calculate your return on investment:
The value of your Google Ads campaign is probably greater than what you'll calculate here, because of the conversions and brand exposure that can't always be tracked. But to estimate your minimum return on investment, subtract your costs from your revenue. For instance, $1500 total revenue - $1425 total cost = $75 total profit.