Hole Spacing & Bolt Pattern

Plan, mark, and drill perfectly placed holes in seconds. Hole Spacing & Bolt Pattern is the professional layout calculator for engineers, machinists, woodworkers, metal fabricators, and serious DIY makers who need exact hole centres and drill templates every time. Whether you are laying out a flange, designing a CNC job, building a drilling jig, or marking a mounting plate, this app gives you precise numbers and a clean scaled diagram — right on the workshop floor or in the field. FOUR POWERFUL CALCULATORS • Single Row — Space any number of equal holes along a piece. Use equal end gaps or set first and last gap independently. Supports length, width, hole diameter, centre offset, and corner radius. • Variable Diameter Row — Lay out a row of different-size holes. Choose top, middle, or bottom alignment and get every gap, centre, and edge position automatically. • Rectangular Grid — Generate rectangular or staggered (diagonal-offset) drilling patterns with border margins, corner radii, and custom hole counts across and down. • Circular & Oval — Build PCD (pitch circle) and oval hole layouts with multiple rings. Even spacing, custom inner and outer margins, custom holes-per-ring, and golden-ratio oval support. DESIGNED FOR PROFESSIONALS • Metric (mm) and Imperial inches; decimal or fractional entry (e.g. 5 1/2") • Hole shapes: round, square, triangle, pentagon, hexagon, heptagon, octagon, star • Dot, cross, number, or diameter centre marks • Live interactive diagrams — pinch to zoom, drag to pan • Running points to hole centres and hole edges, ready to transfer to a ruler or tape • Optional wood or metal material preview • Bounding-circle display for non-round shapes • Full dark mode, iPhone, and iPad support SHARE AND DOCUMENT Every calculation exports as a clean multi-page PDF containing all input parameters, output values, running-point lists, and a scaled diagram — perfect for shop drawings, client approvals, and project records. Share via AirDrop, Mail, Messages, Files, or print directly. BUILT FOR ACCURACY Every engine is carefully ported from the trusted web formulas that engineers already rely on, with validated math, tolerance-aware checks, and clear error messages when a layout will not fit the piece. Stop guessing hole positions. Stop redoing layouts because a gap is off. Download Hole Spacing & Bolt Pattern and get your drilling, fabrication, and layout work right the first time.