Free Measuring Tools: Ring Sizer, Converters and Printable Charts

Every tool on mmintoinches.com in one place. Find your ring size, convert millimetres to inches with exact fractions, or print an actual-size chart for the workshop. All free, no sign-up, and built on the exact definition 1 inch = 25.4 mm.

Sizing tools

New Ring Sizer Tool Find your ring size online or print an actual-size ring sizer. US, UK and EU sizes with diameter and circumference in mm.

Printable Ruler Actual-size ruler in inches, cm and mm, with fraction markings. Coming soon.

Pupil Distance (PD) Ruler Measure your PD at home for ordering glasses online. Coming soon.

Unit converters

MM to Inches ConverterDecimal and fractional inches to the nearest 1/64″. Inches to MMConvert inches, including fractions like 5/16″, to millimetres. CM to InchesCentimetres to inches for clothing, screens and DIY. MM to FeetLong measurements in feet and inches for rooms and timber.

Printable charts (PDF)

MM to Inches ChartEvery mm from 1 to 300 with decimal and fraction inches. Inches to MM ChartFractional inches from 1/64″ upward in millimetres. Wrench & Socket Size ChartSAE and metric equivalents side by side.

Measuring tool buying guides

Best Digital Calipers Under $50For 3D printing, jewellery, woodwork and precise small measurements. Best 25 ft Tape MeasuresTop picks for home, DIY and job-site measuring.

Measurement facts worth knowing

1 inch = 25.4 mm exactly. This has been the international definition since 1959.
1 mm = 0.03937 inches, and 1/16″ = 1.5875 mm.
US ring size 7 = 17.3 mm inside diameter. Each half size adds about 0.4 mm.
A bank card is 85.6 mm × 53.98 mm (ISO/IEC 7810 ID-1), which makes it a handy reference for calibrating screens.