Thread percentage calculator
Choose the thread, then either the drill you have or the percentage you want. Works for every UNC, UNF and metric thread in our data, including sizes without their own page.
Thread and drill
Drill for a target % closest drills
Formula: % thread = (major diameter − drill) ÷ (1.299 × pitch) × 100, the basic thread height used by ASME and tap makers. See How we calculate.