Keep measurement scales at the edges of your screen. Show one ruler or all four corners, switch units, and pin multiple X/Y points with axis lines.
Choose a method. Card calibration works on any screen; device and diagonal options are estimates.
Start from the browser’s standard 96 CSS pixels per inch estimate. Screen hardware varies, so use a card when you need better physical accuracy.
Find the exact diagonal in your device’s screen specifications. This method uses the dimensions reported by your browser.
Hold a bank, credit, or ID card against the on-screen outline. Adjust the slider until the long edge matches. On a phone, rotate to landscape if the outline does not fit. This setting is saved in this browser.
Rulers and measurements run locally in this browser.
BFOTKit’s online ruler places measuring scales around the edges of your screen. Show the top, right, bottom, and left rulers together, or turn individual edges off to make more room. Corner caps join the scales into one frame around the screen. Choose millimeters, centimeters, inches, or CSS pixels and read the graduations against a physical object or a detail on screen. The ruler works in desktop, tablet, and mobile browsers without installing an app.
The scales are fixed to the browser window so they stay at the screen edges while you view a page. Enable all four edges to frame the screen, or use the Top, Right, Bottom, and Left controls to choose a smaller set. Opposite sides share the same coordinate direction: values increase from left to right and from top to bottom. Move the pointer to read its live X and Y position in browser CSS pixels or the selected physical unit.
Use Guides to pin dashed horizontal and vertical guide pairs. Use XY pointer to add multiple labeled coordinate markers, each with its own X and Y axis lines. Remove any point from the pinned-points list or clear them all. Press Escape to clear every marker and guide. The fullscreen control gives the ruler more room, while the light-ruler control changes the scale for contrast. The guide section can be hidden when you want a simpler workspace.
Screen sizes, pixel density, and display zoom vary, so a ruler cannot assume that the same number of browser pixels always equals one physical inch. The automatic value, device presets, and diagonal method provide estimates. For better real-world measurements, choose Bank card and adjust the reference outline until its long edge matches a standard card’s 85.60 mm edge. The calibration is stored in this browser on this device. Recalibrate after changing displays or browser zoom.
Use millimeters for small objects and precise dimensions, centimeters for everyday measurements, and inches for imperial measurements. Pixel mode measures CSS pixels on the page and is useful for checking screen layouts or digital artwork. Switch units at any time; the ruler redraws with the chosen graduations.
The ruler and guide lines are drawn locally in your browser. No measurement is uploaded, and no account is required. For a physical object, place it alongside the on-screen marks after calibration. For digital work, pixel mode follows CSS pixels in the browser viewport. Results are approximate if the screen is scaled, zoomed, or calibrated inaccurately.
Keyboard shortcuts: 1 cm · 2 inches · 3 pixels · 4 mm · G guides · P XY pointer · D ruler contrast · F fullscreen · H show or hide this guide · Esc clear placed guides and pointers.
Screen sizes and display scaling differ, so calibrate the ruler on your device. Choose Bank card and adjust the on-screen outline until it matches the long edge of a standard bank card (85.60 mm). Auto, device, and diagonal calibration are estimates.
Choose millimeters (mm), centimeters (cm), inches (in), or CSS pixels (px). The physical units use your saved on-screen calibration; pixels measure browser CSS pixels.
Yes. Turn on the top, right, bottom, and left rulers together, or choose only the edges you need. The rulers meet at the screen corners.
Yes. Turn on XY pointer and click each point you want to mark. Every point keeps its own X and Y axis lines and coordinate label. Remove markers one at a time or clear them all; Escape also clears every marker.
No. The ruler draws measurement marks on your screen and does not request camera access or estimate object size from photos.
The ruler scale continues across the visible screen edge, but a full 12 inches only fits on a display edge that is long enough. Calibrate your screen with a bank card before measuring physical length.
A browser cannot know the physical size of every monitor or phone screen. Calibration adjusts the ruler’s on-screen scale to your display so mm, cm, and inch marks correspond more closely to real-world lengths.
No. The ruler runs in your browser. It does not upload measurement data or require an account.
Yes. Open this online ruler on your phone, choose cm, mm, or inches, and calibrate the display with a standard card. Rotate to landscape if you need more screen length; a small display may not fit a long measurement.
Yes. BFOTKit has a browser-based ruler with millimeter, centimeter, inch, and CSS pixel scales. Calibrate it before using the marks for physical measurements.
On the inch scale, the distance from 0 to 1 is one inch. One inch equals 2.54 centimeters or 25.4 millimeters. Calibrate the screen ruler first for a closer real-world measurement.
Select cm in the online ruler, calibrate your screen if measuring a physical object, and align one end of the object with 0. Read the centimeter mark at the other end; if it does not start at 0, subtract the first reading from the second.
A smartphone can measure with a supported measurement or augmented reality app, or by comparing an object with a calibrated on-screen ruler. BFOTKit uses the display scale and does not estimate an object’s size from a camera image.
This online ruler does not use your camera. It draws measurement marks on the screen; camera-based or augmented reality measuring apps are separate tools and may require a compatible phone.
Yes. Use an online ruler to compare a physical object with calibrated screen marks or check CSS pixel distances on a page. Screen measurements are estimates unless the display is calibrated, so use a physical instrument when precision is critical.
Choose a unit, calibrate the display for physical measurements, and align the object with the 0 mark. Read the scale where the object ends; when it starts at another mark, subtract the start value from the end value.
In Word for the web, open the document for editing, select View, then turn on Ruler. If the option is unavailable in your current view, switch to editing mode or open the document in the desktop app.
Open your document in Word for the web, choose View, and select Ruler. This shows Word’s built-in layout ruler; it is separate from an on-screen physical measuring tool.
PowerPoint for the web does not display rulers or gridlines. It provides smart guides for aligning objects; to show the horizontal and vertical rulers, open the presentation in the desktop PowerPoint app and choose View > Ruler.
Choose inches, cm, mm, or pixels. For a physical item, calibrate the screen, place one end beside 0, and read the mark at the other end. Turn screen-edge rulers on or off to suit your workspace.
In Word for the web, open the document in editing mode, select View, and enable Ruler. The built-in ruler helps with document layout and is not a physical screen ruler.
Select a unit and use the on-screen marks to check an object or screen layout. Calibrate with a standard card before measuring physical length, then align the object with 0 and read its endpoint.