These are separate sites, each one a reference for a different trade. Each description is the site's own.
- ThreadRefThread and fastener reference for 228+ sizes: metric, Unified and pipe threads with tap drills, clearance holes, torque estimates and wrench sizes.
- EngiRef119 engineering formulas with solvers, 56 materials, 134 unit conversions, constants and reference tables. Free, offline-capable and browser-local.
- SpanRefPublished lumber span tables for floor joists, ceiling joists, rafters and decks, with instant span lookup, a deck calculator and reverse sizing.
- AmpSizerWire size, ampacity, voltage drop and conduit fill calculators built on published 2023 NEC tables, from 14 AWG to 2000 kcmil in copper or aluminum.
- MixRatioConcrete, mortar and grout calculators for slabs, footings, columns and post holes: cubic yards, cubic metres and bag counts, plus 179 worked examples.
- GaugePassFree weld symbol, filler metal, discontinuity and welding math reference, plus practice questions and a gauge trainer for welding inspectors.
Looking for something on this site instead? The fitting identifier, the size reference and the guides are the places most visitors start.