1:1 Precise Online Ruler
Measure objects on your screen, web elements, and other application windows
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PPI atual: 96 (Padrão)
How to use the online ruler
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First-time use: Calibrate the ruler
To ensure the online ruler displays true dimensions, a one-time calibration is required before first use.
Since screen sizes, resolutions, and scaling settings vary across displays, the browser cannot automatically determine the actual physical length of 1 centimeter on your screen. Calibration allows the ruler to adjust its scale to match your specific display, ensuring an accurate 1:1 representation of real-world size.
Click to start calibration →
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Start measuring after calibration
Once calibrated, the ruler on the page will display at its true physical scale.
Simply place physical objects (such as paper, cards, or coins) next to the screen, or move the ruler over the target area to compare.
You can measure a wide range of items, including physical objects, image dimensions on the web, the size of web elements, and other visible content on the page.
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Measure other applications with the standalone ruler window
If you need to measure content outside of your web browser, click here:
Open standalone ruler window →
This opens a separate ruler window.
You can then drag this window to the desired location and adjust its size and position to measure content anywhere on your screen.
The standalone window is ideal for measuring images in viewers, PDF documents, elements in design software, and content in other desktop applications—without being restricted to the web browser.
Tips for measurement accuracy
For more accurate measurements, use a reference object with precise, real-world dimensions during calibration, ensure your browser zoom level is set to 100%, and do not alter system display scaling settings after calibrating.
We recommend recalibrating if you switch monitors or adjust display settings.
Need to measure web elements?
If you frequently need to measure buttons, images, layout dimensions, or other elements on a webpage, try our Chrome extension.
Once installed, you can place a ruler directly onto any webpage without leaving the current page, making measurements much more convenient.
Install Chrome extension →
How to calibrate the online ruler
Please perform a calibration before first use to ensure the ruler displays at true size (1:1).
Calibration steps:
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Select a reference object of known size
Items with fixed dimensions, such as a credit card, A4 paper, or a coin, are recommended.
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Place the reference object next to the screen
Adjust the calibration slider until the reference box on the screen matches the actual size of the object.
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Save the calibration results
Once saved, the ruler will automatically adjust its scale based on your screen settings.
After calibration, you can use the online ruler to measure objects on your screen.
Perguntas frequentes
Basics
Can an online ruler really display actual dimensions? Is it as accurate as a standard ruler?
Yes, it can.
Due to variations in screen size, resolution, and system scaling across different monitors, ruler images on standard web pages often cannot guarantee true-to-life proportions.
The online ruler features a calibration function that allows you to use a reference object of known size—such as a credit card, a sheet of A4 paper, or a coin—to calibrate the display. Once calibrated, the ruler adjusts to your screen's actual dimensions, enabling precise 1:1 measurements.
Why does the online ruler need calibration?
Different devices have varying screen sizes and pixel densities (PPI), meaning a web element of the same size may appear differently on different computers.
Calibration allows the online ruler to calculate your screen's specific scale, thereby converting on-screen lengths into real-world centimeters, millimeters, or inches.
Can I still calibrate the online ruler if I don't have a credit card?
Yes.
The online ruler supports various common reference objects, including A4 paper, credit cards, and coins; you can simply choose a standard item you have on hand to complete the calibration.
Usage Instructions
How do I use the online ruler?
Please complete the screen calibration before using it for the first time.
Once calibrated, place the object you wish to measure next to the screen and use the on-page ruler for comparison.
If you need to measure items in other windows, you can open a separate ruler window and move it to the target location.
The online ruler can measure not only web content but also other objects displayed on your screen.
How do I open a separate ruler window?
Click the Open separate ruler window → button to launch a standalone ruler window.
This separate window can be moved anywhere on your screen, making it convenient to measure images, PDF files, design drafts, and content from other applications.
Can I change the ruler's appearance?
Yes.
The online ruler supports various materials and color styles—such as wood, plastic, and metal—allowing you to choose the look that suits your preference.
Dimensions and Units
Does the online ruler support inches and centimeters?
Yes. The online ruler supports both metric and imperial units, including centimeters, millimeters, and inches. You can switch between units as needed for your measurements. For example, when purchasing clothing, accessories, tools, or parts from different regions that use inch-based sizing, you can measure directly using the imperial scale.
Do I need to recalibrate if I switch computers or monitors?
Yes, calibration data is specific to your current screen.
If you change your computer, monitor, or system display scaling settings, it is recommended to recalibrate to ensure measurement accuracy.
Data and Privacy
Does the online ruler access my browsing history or personal information?
No.
Calibration data and settings are stored locally in your browser; your measurement data or personal information is not uploaded.
Will I lose my calibration data?
Generally, no.
Your calibration settings and unit preferences are saved in your browser, allowing you to use them again when you revisit the page.
However, if you clear your browser data or switch devices, you may need to recalibrate.
Technical Issues
Do the wood, plastic, or metal visual effects affect performance?
No.
These material effects are generated using lightweight SVG technology solely for visual appearance; they do not affect measurement accuracy or significantly impact page performance.