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On iPhone, the tabs are Ruler, History, Match Size, Convert, Level (spirit level), and Settings. On iPad with a wide window, the same screens and Tools are in the sidebar.

• Ruler: two markers in Single mode, and Long (slide along) mode for objects longer than the screen. Fine buttons move the selected marker 0.1 mm (0.01 in) per tap, and Snap (on by default) makes the markers stop on the ruler's finest ticks. Under the reading, the Ruler shows a rough error range and what it is based on (see “How accurate is the ruler?”). Copy measurement copies the reading; Save measurement adds it to History
• Convert: converts between cm, inches, and mm, and has an ordinal date tool (day of year and YYDDD code)

The other tools are under Tools (on iPhone, Tools at the top left of the Ruler screen):

• Measure: Camera Measure (AR) — length, path, height, angle, area, volume, and circle, with plan export (PNG/PDF) as a top view; Photo Dimensions; Protractor; Print a Ruler; Ring size; and Real size of shop items
• Sensors: Plumb Line, Altimeter & Barometer, and Sound Meter

Quick ways to open the ruler: the Home Screen and Lock Screen widget, the Open Ruler control in Control Center or the Action button (iOS 18 or later), and Siri or the Shortcuts app (for example, “Open the ruler in RulerApp”). In Safari, you can select a size written on a page and choose RulerApp in the share sheet to see it at real size.

Ring size, the Camera Measure (AR) modes other than Distance and plan export, Photo Dimensions, and unlimited History with Export all are included in Full Access. Distance in Camera Measure (AR) is free.

After you first save or copy a measurement, the app may ask you to rate it with Apple's standard review prompt. iOS decides whether the prompt appears, and you can simply close it.

Open Match Size. Place a standard credit card (or any card matching ISO/IEC 7810 ID-1: 85.6 × 53.98 mm) on the outline and adjust the slider until the edges match exactly.

If the whole card does not fit on the screen (for example, on iPhone in portrait), the app shows a line with a stop at each end instead of the outline. Lay the card edge named on the screen along the line — the long edge (85.6 mm) or the short edge (53.98 mm) — and adjust the slider until both ends of that edge meet the stops.

Then tap Save. The value is not saved until you tap Save; after that it is kept between sessions.

The Ruler's unit switch has two units: centimeters (cm) and inches (in).

• In cm, the reading is also shown in millimeters (mm); in inches, it is also shown as a fraction (to 1/16 in)
• Convert converts between cm, inches, and mm

Millimeters are shown and converted, but are not a separate choice in the unit switch.

Under the reading, the Ruler shows a rough error range (for example “±0.3 mm”) and what it is based on. The range grows with the length being measured, so there is no single fixed accuracy.

• After Match Size with a card: about 0.3% of the length, plus one screen pixel at each end
• Before matching, using the app's table of screen sizes: about 0.5% of the length, plus one pixel at each end
• If your model's screen size is not in the table, the app shows “Accuracy unknown” and asks you to match the size with a card first

These ranges are estimates, not measured values. Note that screen-based rulers are intended for quick reference measurements and may not replace precision instruments for professional use.

Yes, RulerApp works on both iPhone and iPad. Match Size is saved on each device separately, since screen sizes and pixel densities differ between devices.

On iPad, you benefit from a larger measuring surface, allowing you to measure longer objects without repositioning.

In Single mode, drag the two markers along the ruler to measure a specific segment. The distance between the markers is displayed in your selected unit. Use the fine buttons to move the selected marker in small steps, and keep Snap on (the default) to stop the markers on the ticks, or turn it off to place them freely.

For an object longer than the screen, switch the top selector to Long (slide along). At the end of the screen, mark the object at the end marker, tap Mark & Continue, slide the device so the 0 edge is on the mark, and keep measuring.

Purchase Full Access (a one-time in-app purchase) to remove ads and save unlimited measurements. To restore a previous purchase, open the Full Access screen and tap Restore Purchases. If you bought an earlier paid version of RulerApp, Full Access is applied automatically.

Your Match Size value, unit preferences, and saved measurements are stored on your device and are not sent to the developer. Only the Match Size value is also copied to an App Group on the same device, so that the RulerApp share extension can use it. Like other app data, they can be included in your iCloud or computer backups. They leave the app only when you share, export, or copy them yourself.

The free version shows banner ads served by Google AdMob. The Google Mobile Ads and User Messaging Platform SDKs in the app collect data such as IP address (which may be used to estimate coarse location), device identifiers, ad and interaction data, and diagnostic data for advertising and analytics. The one-time Full Access purchase removes ads.

The camera, microphone, location, and motion sensors are used on your device only in the tools that need them. The Sound Meter does not record audio.

See our Privacy Policy for full details.

iPhoneのタブは「定規」「履歴」「長さ合わせ」「換算」「水準器」「設定」です。iPadの横幅が広い画面では、同じ画面と「ツール」がサイドバーにあります。

• 定規: 2つのマーカーで測る「ふつう」と、画面より長い物を測る「長い物（ずらして測る）」。微調整のボタンで選んだマーカーを1回0.1mm（0.01インチ）ずつ動かせ、「吸着」（最初はオン）でマーカーが一番細かい目盛りに止まります。値の下には誤差の目安とその根拠を表示します（「どのくらい正確ですか？」を参照）。「測定値をコピー」で値をコピー、「測定を保存」で履歴に残せます
• 換算: cm・インチ・mmの換算と、通し日付（年の何日目か・YYDDDコード）

他の道具は「ツール」にあります（iPhoneは定規の画面の左上）:

• 測る: カメラで測る（AR。距離・折れ線・高さ・角度・面積・体積・円、上から見た平面図のPNG/PDF書き出し）、写真に寸法を書く、分度器、定規を印刷、指輪のサイズ、通販の寸法を実寸で見る
• センサー: 下げ振り、気圧・標高計、騒音計

定規をすぐ開く方法: ホーム画面・ロック画面のウィジェット、コントロールセンターやアクションボタンの「定規を開く」（iOS 18以降）、Siriやショートカット（例:「RulerAppで定規を開く」）。Safariでページの寸法を選び、共有シートでRulerAppを選ぶと実寸で表示できます。

指輪のサイズ、カメラで測る（AR）の距離以外の測り方と図面の書き出し、写真に寸法を書く、履歴の無制限保存と一括出力はFull Accessに含まれます。カメラで測る（AR）の距離は無料です。

初めて測定値を保存またはコピーしたあと、Apple標準の評価のお願いを表示することがあります。表示するかどうかはiOSが決め、そのまま閉じてもかまいません。

「長さ合わせ」を開き、クレジットカードなど標準サイズのカード（ISO/IEC 7810 ID-1: 85.6 × 53.98 mm）を枠に重ね、端がぴったり合うようスライダーで調整します。

カード全体が画面に収まらないとき（iPhoneの縦向きなど）は、枠の代わりに両端に印の付いた線を表示します。画面に書かれたほうの辺（長い辺 85.6mm または短い辺 53.98mm）を線に沿わせ、その辺の両端が印に合うようスライダーで調整します。

最後に「保存」を押してください。「保存」を押すまで値は保存されません。保存した値は次に開いたときも使われます。

定規の単位の切り替えは、cmとインチの2つです。cmのときはmmでも、インチのときは分数（1/16インチ単位）でも値を表示します。「換算」ではcm・インチ・mmを相互に換算できます。mmは表示と換算で使え、単位の切り替えの選択肢にはありません。

定規の値の下に、誤差の目安（例:「±0.3 mm」）と、その根拠を表示します。目安は測る長さによって変わり、一律の精度ではありません。

• カードで長さ合わせをしたあと: 長さの約0.3%＋両端の画面1画素ぶん
• 長さ合わせの前（機種の仕様から）: 長さの約0.5%＋両端の画面1画素ぶん
• 機種の画面サイズがアプリの表に無いときは「誤差不明」と表示し、先にカードで長さを合わせるよう案内します

これらは見込みの値で、実測した精度ではありません。画面の定規は手早く測るためのもので、精密な測定器の代わりにはなりません。

長さ合わせの値・単位設定・保存した測定値は端末内に保存し、開発者には送りません。共有の拡張が使えるよう、同じ端末内のApp Groupに写すのは長さ合わせの値だけです。他のアプリのデータと同じく、iCloud・パソコンのバックアップに含まれることがあります。アプリの外に出るのは、お客様が共有・書き出し・コピーをしたときだけです。

無料版はGoogle AdMobの広告を表示し、アプリに組み込んだGoogleのSDKが、IPアドレス（おおよその位置の推定に使われることがあります）・デバイス識別子・広告と操作の情報・診断情報を広告と分析のために収集します。Full Accessを購入すると広告は表示されません。詳しくはプライバシーポリシーをご覧ください。