How this tool works
One international inch is exactly 25.4 millimetres. Enter either field and the other updates immediately; the fractional result rounds the inch value to the nearest sixteenth.
Home / Inches and millimetres
Inches ↔ Millimetres
A bidirectional dimension tool for exact decimal conversion plus a practical fractional-inch interpretation.
Exact relationship1 in = 25.4 mm
Nearest 1/16 inch—
When it is useful
Useful for hardware, product dimensions, 3D printing, woodworking, machining and drawings that cross between metric and imperial systems.
Accuracy and unit standards
The decimal conversion is exact before display rounding. The nearest fraction is intentionally approximate and should not replace specified engineering tolerances.