How I built a blazing fast AI ROI Calculator in Vanilla JS

As developers and agency owners, we often need to justify the cost of AI API integrations to clients or ourselves. I was tired of guessing the break-even points, so I built a clean, client-side AI ROI Calculator.

The Approach

I wanted to keep it 100% Vanilla JS for maximum performance and security. No server calls, complete data privacy for sensitive financial inputs.

Here is a quick look at how the core calculation logic handles the monthly cost comparison:

function calculateROI(humanHours, hourlyRate, apiCostPerMonth) {
    const currentMonthlyCost = humanHours * hourlyRate;
    const savings = currentMonthlyCost - apiCostPerMonth;

    if (savings > 0) {
        return { isProfitable: true, monthlySavings: savings };
    }
    return { isProfitable: false, monthlyLoss: Math.abs(savings) };
}

Try it out

You can use the live tool for free here: AI ROI Calculator

Let me know what you think or if you'd add any specific API pricing presets in the comments!