Everybody has that one shirt — it looks good and, more importantly, fits perfectly. Use that shirt to find other great-fitting tops with Fit Finder, an impressively detailed database and web app.
Pick out that perfect shirt by brand and size, whether it's a simple T-shirt or a buttoned dress shirt with general size. Get specific in describing how it fits your neck, chest and other qualifications, then run it through Fit Finder. You'll get results showing the best matches to other brands, their specific sizing details and links to specific shirts available for purchase in that size, if available. Even if you don't find your next perfect shirt, you'll learn a bit about your sizing and how other shops measure their goods.
Fit Finder doesn't require sign-up or anything else to use, other than your browser. It's a stunningly specific counterpoint to, say, the world of men's pants, where waist measurements are entirely unreliable. Thanks for the tip, Kendall!