Ruler: CM, MM & Inches
Actual Size, Auto-Calibrated
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
Engineered to universally adapt to any screen size. Get 1:1 actual-size physical accuracy across all iPhone & iPad models in cm, mm & inches, dual-jaw caliper mode.
The only physical ruler engineered to universally adapt to any screen size with guaranteed 1:1 actual-size accuracy.
Unlike ordinary ruler apps that lose precision across different devices, "Ruler: CM, MM & Inches" features an intelligent hardware display adaptation engine. Whether you are using a compact screen, the largest Pro Max, or a giant iPad tablet, 1 centimeter on your screen is strictly 1 centimeter in the physical world.
UNIVERSAL ADAPTIVE PRECISION:
• Adapts to Any Screen Size & Aspect Ratio
From compact phones to large-screen devices and iPad tablets, our advanced display geometry engine automatically maps your screen’s native hardware dots-per-inch (DPI) for flawless real-world fidelity.
• Guaranteed 1:1 Actual Size
No camera distortion, no AR scanning lag, and no complicated setup. Just place your object directly on the glass and measure with real-world physical certainty.
• Dual-Edge Simultaneous Measurement
Metric scale (cm & mm) along the left edge, Imperial scale (inches with 1/16" graduations) along the right edge—always visible at the same time.
• Precision Caliper Mode (Pinch to Measure)
Activate dual adjustable caliper jaws with live dimension arrows and real-time thickness readouts. Perfect for measuring coins, screws, jewelry, and hardware parts.
• Universal Card Calibration
Verify or fine-tune your device’s accuracy anywhere in the world using any standard credit, debit, or ID card (ISO ID-1 standard 53.98 mm).
• High-Contrast Dark & Light Themes
Switch instantly between a glare-free OLED dark mode and an ultra-sharp, high-contrast black-on-white theme designed for outdoor visibility.
• 100% Offline & Private
No internet required, no background tracking, and no sign-in. Your pocket ruler is always ready when you need it.
From DIY crafts and carpentry to daily household measuring, carry a certified actual-size ruler tailored to your exact screen.
Ratings & Reviews
Bug fixes
The developer, Tianyu Lu, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Location
- Identifiers
- Usage Data
- Diagnostics
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Tianyu Lu
- Size
- 3.3 MB
- Category
- Utilities
- Compatibility
Requires iOS 16.0 or later.
- iPhone
Requires iOS 16.0 or later. - iPad
Requires iPadOS 16.0 or later. - Mac
Requires macOS 13.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Contains
Advertising
- In-App Purchases
Yes
- Remove Ads & Unlock Full Ruler $1.99
- Copyright
- © 2026 Tianyu Lu