TrueSizeLumber exists to answer one recurring jobsite question: "wait, what does this actually measure?" It's a free lookup and calculator tool for builders, DIYers, and anyone standing in a hardware store aisle trying to convert a nominal size into a real one.
Nominal sizing is one of the most common sources of confusion in construction and home improvement. A "2x4" isn't 2"×4". A "3/4-inch" sheet of plywood usually isn't 3/4" thick. A "1/2-inch" PVC pipe doesn't measure 1/2" on the outside or the inside. None of that is a secret to people who've been building for years — but it trips up beginners constantly, and even experienced builders sometimes need a fast reference instead of relying on memory.
TrueSizeLumber pulls that information into one place: dimensional lumber, common fasteners (bolts, screws, nails, anchors, lag bolts, rebar), and pipe (PVC, copper, Schedule 40 steel) — each with the nominal name next to the actual, measurable dimension, plus calculators that use the real numbers instead of the rounded ones.
Dimensional softwood lumber sizes follow the American Softwood Lumber Standard (maintained with reference to USDA Forest Products Laboratory research). Fastener specifications follow ANSI standards. Pipe dimensions follow ASME/ASTM standards for the relevant material (PVC, copper Type M, Schedule 40 steel). These are industry-standard figures, not measurements from a single supplier — but manufacturing tolerances exist, so always confirm against your actual materials before a cut you can't undo.
TrueSizeLumber is an independently run reference site. There's no login, no account, and no paywall — the lookup tool, calculators, and guides are free to use. The site is supported by advertising, which helps cover hosting and keeps the tool free. See the Privacy Policy for details on data collection and advertising.
Spot something that looks wrong, or want to suggest a size that's missing? Get in touch — corrections get fixed quickly since the whole point of this site is accuracy.