What's the optimal button size for mobile checkout?

As a Shopify store owner, I've been obsessing over mobile conversion rates, and button sizes are driving me crazy. Every time I look at my analytics, I see mobile users starting checkout but not completing it. It's frustrating because I know the problem isn't my product—it's likely my user interface. I've watched session recordings where potential customers struggle to tap buttons, either accidentally hitting the wrong element or getting frustrated by tiny, cramped touch targets. My conversion rate on mobile is about 40% lower than desktop, which is essentially leaving money on the table. I've tried guessing at button sizes, but without a systematic approach, I'm basically throwing darts blindfolded. What I need is a data-driven strategy that considers finger sizes, tap accuracy, and mobile user experience psychology. I want buttons that are large enough to be easily tappable but not so massive that they overwhelm my clean, minimalist design. This isn't just about aesthetics—it's about creating a frictionless path to purchase that respects my customers' time and makes buying from my store feel effortless. The stakes are high: even a 5% improvement in mobile conversion could mean thousands in additional monthly revenue.