# Ruler: CM, MM & Inches — Measure Length & Caliper Tool

> Accurate, adaptive physical ruler app for precise measurements on any screen. (iPhone/iPad app by Tianyu Lu.)

- Source: https://appshunter.io/ios/app/ruler-cm-mm-and-inches/id6815516308 (this page in markdown: same URL + `.md`)
- Developer: [Tianyu Lu](https://appshunter.io/developer/6810794695)
- Category: Utilities, Productivity
- Price: Free with in-app purchases
- Rating: 5.00/5 from 2 App Store ratings · 1 written reviews indexed
- Age rating: 4+
- Requires: iOS 16.0 · 3 MB
- Languages: American English, Arabic, Czech, Danish, Dutch, Finnish, French (France), German (Germany), Hebrew, Hindi and 17 more
- Released: 2026-09-29
- Data updated: 2026-10-31
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/ruler-cm-mm-and-inches/id6815516308/reviews.md

## What is Ruler?

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.

## Key features

- Actual-size accuracy on any screen
- Dual-edge metric and imperial scales
- Precision caliper mode for thickness
- Universal card calibration
- High-contrast dark and light themes
- 100% offline and private

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Remove Ads & Unlock Full Ruler | $1.99 | one-time |


## Is Ruler safe?

Not enough ratings yet to assess Ruler.

## Is Ruler legit?

Ruler: CM, MM & Inches appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for Ruler is 65 out of 100 points across 7 verification signals from App Store and developer data.

## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/ruler-cm-mm-and-inches/id6815516308/reviews.md

### 5/5 — Really handy!

*2026-10-21*

Super easy to use. Comes in handy when I need to measure something real quick!

## Frequently asked questions about Ruler

### How does Ruler ensure actual-size accuracy on different devices?

Ruler uses an intelligent hardware display adaptation engine that maps your device's native dots-per-inch (DPI) to guarantee 1:1 actual-size fidelity. This ensures that 1 centimeter on your screen is precisely 1 centimeter in the physical world, regardless of screen size or aspect ratio.

### Can Ruler measure in both centimeters and inches simultaneously?

Yes, Ruler features dual-edge simultaneous measurement. The left edge displays the metric scale (cm & mm), while the right edge shows the Imperial scale (inches with 1/16" graduations), both visible at the same time.

### What is the precision caliper mode in Ruler?

The precision caliper mode allows you to activate dual adjustable caliper jaws by pinching. It displays live dimension arrows and real-time thickness readouts, making it ideal for measuring small objects like coins, screws, or jewelry with high accuracy.

### How do I calibrate Ruler for my device?

Ruler offers Universal Card Calibration, allowing you to verify or fine-tune your device's accuracy using any standard credit, debit, or ID card (ISO ID-1 standard 53.98 mm). This ensures precise measurements anywhere in the world.

### Does Ruler work offline?

Yes, Ruler is 100% offline and private. No internet connection is required, and there is no background tracking or sign-in needed, ensuring your measuring tool is always ready when you are.

### What themes are available in Ruler?

Ruler offers high-contrast dark and light themes. You can switch between a glare-free OLED dark mode and an ultra-sharp, high-contrast black-on-white theme designed for optimal visibility, even outdoors.

### Is Ruler suitable for all screen sizes?

Yes, Ruler is engineered to universally adapt to any screen size and aspect ratio, from compact phones to large-screen devices and iPad tablets. Its adaptive precision engine ensures accurate measurements across all supported devices.

### Does Ruler have ads?

Yes, Ruler contains advertisements. As a free application with in-app purchases, advertisements are displayed to support its development and availability.

## Version history (last 5 releases)

### 1.0.6 — 2026-10-24

Added support for iPhone Duo.

### 1.0.5 — 2026-10-18

Bug fixes

### 1.0.4 — 2026-10-17

• Added full localization support for 28 languages, seamlessly adapting to your device's preferred language.
• Optimized typography and layout spacing for multi-language display.
• Overall performance enhancements and bug fixes.

### 1.0.3 — 2026-10-01

Bug fixes

### 1.0.2 — 2026-09-29

No release notes.

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## More apps by Tianyu Lu

- [2048 Twisted](https://appshunter.io/ios/app/2048-twisted/id6810794693)
- [Sudoku: Pieces - Block Jigsaw](https://appshunter.io/ios/app/sudoku-pieces-block-jigsaw/id6810938707)
- [Mahjong Mixup](https://appshunter.io/ios/app/mahjong-mixup/id6814936261)
- [Bubble Level: Spirit & Angle](https://appshunter.io/ios/app/bubble-level-spirit-and-angle/id6816330217)
- [Skillball Rally - Marble Race](https://appshunter.io/ios/app/skillball-rally-marble-race/id6819093734)

All apps by Tianyu Lu: https://appshunter.io/developer/6810794695

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-31.*