オンライン定規 — 原寸大・実寸サイズ（cm・mm・インチ・ピクセル対応）
スマホやPCの画面で実寸サイズが測れる無料オンライン定規。カード校正、4辺ベゼル定規、リングサイズ測定、デバイス自動検出完備。
METRIC (TOP/LEFT) · INCHES (BOTTOM/RIGHT)
2D Measurement (Width × Height) · estimated
📋 Session Measurement Log (0)
No saved measurements yet. Click [+ Log] above to record measurements during your session.
Place physical items against any active screen edge ruler, or drag points A and B to measure length and height. Select A or B to nudge with Arrow keys (1 mm / 1/16″) or Shift + Arrow keys for fine-tuning in 0.1 mm increments.
21.2 cm × 6.9 cm visible · Accuracy depends on calibration4-Edge Bezel Scales · Local measurements · No upload or account
01
Auto-Detect & Calibration
Screen resolution and DPR are auto-detected on load. Match any standard bank card to lock 100% true physical scale.
02
Measure Center or Screen Edges
Use Points A & B for millimeter/inch dimensions, or activate Bezel Mode to align physical objects directly against your monitor frame.
03
Ring Sizer & Coins
Switch to Ring Sizer mode to determine your exact US, UK, EU, or JP ring size with on-screen circles and standard coin references.