The Loom's Legacy: Why are standard fabric widths so weird? 36, 45, 54, 60 inches? It all comes down to the human body and the mechanics of weaving. Historically, a "handloom" was limited by how far a weaver could throw the shuttle—usually about 27 to 36 inches. As industrial power looms took over, widths standardized based on efficiency.
The Standards: 36" (90cm): Old standard, common for vintage calicos and quilting cottons (though now mostly 42-44"). 45" (115cm): The modern standard for quilting cotton and apparel fabric. 54-60" (140-150cm): Standard for apparel wool, knits, and upholstery. Wider looms mean less waste for garment factories. 108" (275cm): "Wideback" fabric specifically for quilt backings so you don't have to piece them.
Modern Application: You find a vintage dress pattern requiring 4 yards of 35" fabric. You want to make it in a modern 60" wide wool knit. If you just buy 4 yards, you'll have massive waste. This tool calculates that you only need 2.33 yards. That's money saved!
Warning on Layouts: This math assumes the total surface area is the same. It does NOT account for pattern piece shapes! If you have a wide circle skirt piece that is 40" wide, you simply cannot fit it onto 36" fabric, no matter what the math says. Always check if your widest pattern piece actually fits the new bolt width.