Ring Sizing
Measure Inside Ring Diameter
Lay a ring flat on the screen so the inner band encloses the blue circle. Read US half-sizes (3–13) and EU circumference sizes automatically.
True-Scale Concentric Metrology · 1.00 mm – 150.00 mm
Circle, Ring, Bolt & Coin Diameter Gauge
Place any ring, washer, screw head, coin, or pipe gasket directly onto the calibrated live circle—or drag the rim until it fits flush.
96.0 PPI
Quick Reference Presets (ISO Bolts, US Rings, Coins, Discs)
Live Geometric Readout
- Diameter
- 24.26 mm
- Radius (r)
- 12.13 mm
- Circumference (π·d)
- 76.22 mm
- Area (π·r²)
- 462.2 mm²
- Diameter (Inches)
- 0.955 in
- Screen Diameter (px)
- 92 px
- Nearest Ring Size
- —
Hardware & Bolts
Check M3–M12 Clearance & Washers
Compare metric machine screw heads, nylon washers, O-rings, and drill shanks from 1 mm up to 150 mm.
Calibration Accuracy
Requires Display Calibration
Like any optical overlay, circle diameter accuracy depends on prior ISO ID-1 card or diagonal screen calibration.