Measurement Tool

Free Online Screen Ruler Measure in Pixels, CM, MM & Inches

Measure anything on your screen in pixels, centimetres, inches or millimetres. Drag to measure, adjustable DPI — no download needed.

Unit
Direction
DPI
0 px
1

Set your DPI

Click "Auto" to detect your screen DPI, or enter it manually for accurate cm/mm/inch measurements.

2

Drag to measure

Click and drag anywhere on the ruler to create a measurement range. The exact size is shown live.

3

Switch units

Toggle between PX, CM, MM and IN anytime. Flip to Vertical for height measurements.

How to Use the Screen Ruler

1

Set Your DPI

Click "Auto" to detect your screen DPI automatically, or enter it manually to ensure highly accurate physical measurements.

2

Drag to Measure

Click and drag anywhere inside the ruler canvas to create a measurement range. The exact dimensions update live.

3

Switch Units & Orientation

Toggle between Pixels (PX), Centimeters (CM), Millimeters (MM), and Inches (IN). Flip to vertical mode for height tracking.

Frequently Asked Questions

How accurate is this online ruler?
Accuracy depends on your screen's DPI (dots per inch). Use the "Auto Detect" button to get the most precise DPI for your display. For standard 96 DPI monitors the ruler is very accurate. High-DPI / Retina screens may need a manual adjustment.
What does DPI mean and why does it matter?
DPI (Dots Per Inch) is the number of pixels in one inch of your screen. The default is 96 DPI for most Windows monitors. MacBook Retina displays are typically 144–220 DPI. Setting the correct DPI is essential for accurate cm, mm and inch measurements.
Can I use this ruler to measure objects on screen?
Yes. Hold a physical object against your screen next to the ruler and read the measurement. Make sure your DPI is correctly set for the most accurate physical measurements.
How do I switch between horizontal and vertical?
Click the "Horizontal" or "Vertical" button in the controls bar. The ruler will rotate automatically. Vertical mode is useful for measuring heights and portrait-oriented objects.
Can I measure in centimetres, inches or millimetres?
Yes. Click the CM, MM or IN buttons in the controls bar to switch units instantly. The ruler recalculates all tick marks in real time. For accurate physical measurements in centimetres or inches, make sure your DPI is set correctly first — use the Auto Detect button.
Does this ruler work on Mac, Retina or high-DPI displays?
Yes. MacBook Retina and other high-DPI displays typically have a DPI of 144–220 rather than the standard 96. Click Auto Detect to automatically calculate your screen's DPI, or enter it manually. This ensures centimetre and inch measurements are physically accurate on your device.
Do I need to download or install anything?
No. This is a 100% browser-based online ruler — no download, no installation, and no account required. It works on any device including Windows, Mac, Linux, iPhone and Android. All calculations happen locally in your browser.
Is this screen ruler useful for web and UI design?
Yes. Developers and designers use it to measure element dimensions, check spacing, verify padding and margins directly on screen — without opening browser DevTools or Figma. Switch to PX mode and drag across any UI element to instantly read its pixel width or height.
How do I reset or clear a measurement?
Double-click anywhere on the ruler to clear the current measurement and reset to zero. You can then drag again to start a new measurement. The live readout in the top-right always shows your current position or the measured distance.
Is this an actual size ruler?
Yes. After setting the correct DPI, the ruler can display measurements in actual physical size using centimeters, millimeters, or inches.
Can I use this ruler on a phone or tablet?
Yes. The online ruler works on smartphones, tablets, laptops, and desktop computers. Calibration may be required for maximum accuracy.
What is the difference between pixels and inches?
Pixels are digital units used on screens, while inches are physical units of length. The ruler converts pixels into real-world measurements using your display's DPI value.
Can I measure website elements with this ruler?
Yes. Many web designers and developers use the ruler to measure buttons, images, spacing, margins, and other interface components directly on screen.

Accurate Pixel and Physical Dimension Measurement Tool

Precision Measurements for Web & UI Design

Developers and designers often need to verify element dimensions, margins, or padding directly on a live webpage without opening heavy inspection tools. Our online screen ruler provides a fast, lightweight alternative. Whether you are checking CSS box models or verifying UI element alignment, you can instantly read dimensions in pixels with high precision.

Calibrated Physical Measurements

Need to measure a physical object using your screen? By using our Auto-DPI calibration, the tool adjusts to your screen's specific hardware density. This ensures that when you switch to centimeters, inches, or millimeters, the output corresponds to real-world measurements, making this a highly versatile digital ruler for quick physical tasks.

Privacy-First, Free with No Download

This utility is completely browser-based. There are no background applications to install and no tracking software hidden within the code. Every calculation executes locally on your hardware, ensuring that your workflow and screen data remain private. Get reliable measurement results for free with no registration required and no downloads necessary.

Actual Size Ruler Online

ToolTiny provides an actual size ruler online that can display measurements in centimeters, millimeters, inches, and pixels. By setting the correct DPI, the ruler matches real-world dimensions on your screen.

This makes it useful for measuring small physical objects, printed materials, and screen elements without installing any software.

Virtual Ruler for Any Device

This virtual ruler works directly in your browser and supports desktop computers, laptops, tablets, and smartphones.

Whether you use Windows, macOS, Linux, Android, or iPhone, the ruler adapts to your screen and provides accurate measurements after calibration.

Pixel Measurement Tool for Designers and Developers

As a professional pixel measurement tool, this ruler helps web designers and front-end developers verify spacing, alignment, margins, and element sizes directly on screen.

It is especially useful for responsive design testing, UI reviews, and layout validation without opening additional software.

Measure Screen Size Online

Need to measure a screen element quickly? This online measuring tool lets you drag across any visible area and instantly read the size in pixels, centimeters, millimeters, or inches.

The tool is ideal for measuring images, UI components, documents, screenshots, and presentation slides displayed on your monitor.

Related Design & Dev Tools

Community Comments

500 left
500 characters remaining
Loading comments...