Monitor Geometry Test – Free Online Monitor Test
Monitor Geometry Test. Click Enter Fullscreen to run this monitor geometry test and check the border, grid and circle for distortion or overscan. Run the ips glow test for a few seconds under normal room lighting for the most reliable result.
Interactive Tool
Geometry & Overscan Canvas
The outer border sits one pixel inside the true edge — if any side of it is missing once you're fullscreen, that edge is being overscanned and cropped.
Grid & Overscan Calculator
The Geometry Alignment Test is a monitor geometry test that renders a full-frame border, a regular grid, and a perfect circle so you can check whether your display is stretching, skewing, or cropping the picture. Click Enter Fullscreen and look for two things: the border should stay fully visible right to the screen edge — if it's cut off, your TV or monitor is overscanning and cropping part of the image — and the circle should render perfectly round, since an oval shape means the pixels aren't square or the aspect ratio is being scaled incorrectly. Most relevant if you're using a TV as a monitor, where overscan silently eats a chunk of your desktop.
The monitor geometry alignment test is a monitor geometry test that draws a full-screen grid, border and circles so you can spot stretching, cropping and skewed edges in seconds. Run it in fullscreen: circles should look round, cells should match, and every border line should stay visible. Anything else points to overscan, wrong scaling or a misaligned panel.
How the Monitor Geometry Alignment Test Works
Geometry patterns give your eye straight references. Wherever a line bends or a shape changes size, something altered the picture on its way to your display, and this distortion becomes obvious. Use the monitor input lag test to confirm whether your monitor shows this issue before you adjust settings or return it.
Circles, Equal Sides and Grid Lines
Circles must stay round, squares keep equal sides and every cell holds the same size. Straight lines also reveal tilt or rotation.
Aspect Ratio, Overscan and Cropping
A wrong aspect ratio makes circles stretch into ovals. Overscan enlarges the picture and hides the border, a cropping effect common on TVs. A forced zoom or aspect mode on the source causes the same symptoms.
Prepare Your Screen Tester Setup
Let the panel warm up for 15 to 30 minutes in a dark room and wipe off dust that could pass for dead pixels. Use proper cables, connect straight to the GPU and update the driver, because HDMI converters and drivers can add scaling. Dust, drift and scaling must not masquerade as a geometry fault in the grid you are about to read.
Set Native Resolution and Fullscreen Mode
Pick the native resolution in your display settings, disable OSD enhancements, then press F11 so the pattern covers every pixel, with no tinted color mode active.
Run the Geometry Tests Step by Step
- Open the tool in your browser, choose a pattern and press F11 for fullscreen; the keyboard arrows switch patterns.
- Check that the circles are round and the border sits inside every corner and edge.
- Adjust size, position and focus if your monitor has controls; lower the contrast to sharpen thin lines.
- Cycle each color and confirm the lines and circles keep the same shape in the image.
- Press Esc to leave the pattern.
Photograph the Pattern Without Perspective
Shoot straight on from the center at a normal viewing distance. Angled photos bend lines, so evidence only counts when the picture matches what your eye sees.
Read Test Patterns for Pincushion, Barrel, Trapezoid and Tilt
Match what you see in the test pattern to the table and fix the first mismatch before judging anything else.
| Symptom | Likely cause | What to adjust |
|---|---|---|
| Circles look oval | Wrong aspect ratio, stretched image | Choose 1:1 scaling |
| Border cut off | Overscan changes the size and position | Switch overscan off |
| Pincushion or barrel bowing | CRT or projector lens | Use the geometry controls |
| Trapezoid, tilt or parallelogram | Orthogonality or rotation error | Realign the mount and check again |
| Color fringes at line edges | Convergence or a vivid color mode | Reset the color settings |
| Blurry lines | Focus, sharpness or low contrast | Adjust each test color |
Fine Grid Sampling and Bands
One-pixel lines that shimmer or form bands expose sampling trouble, usually from scaling and rarely a faulty panel. Repeat the test at native resolution before blaming hardware.
Reading the Grid on a 34-Inch Ultrawide Monitor
I just plugged a 34-inch 3440 × 1440 ultrawide into a dock and the photo editor's round vignette looks egg-shaped. Before I blame the app, I want a number, so I open the geometry grid in a screen tester and draw a circle that is 600 pixels tall in the 2560 × 1440 mode the dock picked by default.
On a ruler held to the glass, the circle measures 186.7 mm wide and 138.9 mm tall. The panel is 796.6 mm across, so each of its 3,440 columns is 0.2316 mm wide. The circle should be 600 columns wide at 138.9 mm, yet it is 806 columns wide. That ratio is 186.7 ÷ 138.9 = 1.344, exactly 3440 ÷ 2560, so the dock is widening a 16:9 source across a 43:18 panel. This distortion is not a panel defect, and no geometry control on the monitor will fix it.
I try the three modes the GPU offers and measure again:
| Scaling mode | Circle width × height | Width ÷ height |
|---|---|---|
| Fill screen | 186.7 × 138.9 mm | 1.344 |
| Preserve aspect ratio | 138.9 × 138.9 mm | 1.000 |
| Native 3440 × 1440 | 138.9 × 138.9 mm | 1.000 |
Preserving the aspect ratio fixes the shape but leaves two 440-pixel black bars, about 101.9 mm each, and only 74.4% of the width in use. Native resolution fixes both, so that is the setting I keep. The number to watch is width ÷ height: anything beyond about 1.01 is visible by eye on a large circle, which is why a 0.5% error can pass unnoticed while 34% cannot.
One caveat: if the ruler reads equal but the circle still looks oval from my seat, the cause is viewing angle, not geometry. Ultrawides are curved, so I remeasure from the center of the desk before trusting the result.
Geometry Patterns on CRT, Projector and LCD Screens
Analog CRT monitors and projectors drift, and their color convergence shifts, so correct pincushion and trapezoid with their controls. A CRT may even widen bright areas through high-voltage regulation. Maximize the output image until the dashed line along the edge just stays visible.
Flat Panels Keep a Fixed Matrix
LCD, OLED and IPS flat panels map every pixel to a fixed matrix, so a geometry error nearly always comes from the source rather than the panel. Round shapes should look the same, because the panel drives millions of pixels on a laptop, TV or gaming monitor.
Defective Pixels and Other Monitor Screen Test Checks
Alignment is only one part of image quality, so run these patterns after the grid passes. Fill the screen with solid colors to find stuck pixels and defective pixels, then look for backlight bleed in a dark room. Warranty rules differ by manufacturer, so read them before a return. Color calibration needs a colorimeter, not this grid, though graphic work benefits from both.
Viewing Angle and Circle Shape
Circles should keep their shape off-axis. Gamma and gradients need their own patterns, though smooth gradients without banding show how uniformity, brightness and greyscale hold up.
Motion Checks Beyond Geometry
A moving block reveals ghosting and slow response time, and a refresh rate check confirms the mode set in your settings matches the panel. The grid is static, so motion needs its own pattern.
Worked Example: Reading a Monitor Test on a 24-Inch Display
A 24-inch 1920 × 1080 screen has a pixel pitch of 0.2768 mm, so an 80-pixel cell should measure 22.14 mm. With HDMI overscan at 2.5% per side, 96 columns of pixels vanish and the picture scales up:
$$\text{scale} = \frac{1920}{1920 - 96} = 1.0526$$
| Measurement | Expected | Measured |
|---|---|---|
| Visible width | 1920 px | 1824 px |
| Cell width | 22.14 mm | 23.31 mm |
| Circle diameter | 149.5 mm | 157.3 mm |
| Border lines seen | 4 | 0 |
Retest After Switching Overscan Off
Setting the HDMI mode to 1:1 restores all four border lines and the 22.14 mm cell, which confirms the fault was scaling.
Frequently Asked Questions
- What does a monitor geometry alignment test show?
- It draws a full-screen grid, border, axes and circles so you can see whether the picture is stretched, cropped, tilted or bowed. Circles should stay round, cells should stay equal and every border line should be visible.
- Why must I run the test in fullscreen?
- Fullscreen makes the pattern cover every pixel, so a missing border or an enlarged grid points to overscan or scaling instead of browser chrome hiding part of the picture.
- What is overscan and how do I turn it off?
- Overscan enlarges the picture slightly so its outer edge falls off the screen, a habit inherited from TVs. Choose a 1:1, Just Scan or PC mode in the display or GPU settings, and use the monitor's native resolution.
- Why do circles look like ovals?
- The source is being stretched to a different aspect ratio. Set the scaling mode to preserve aspect ratio or use the native resolution, then remeasure that the width and height match.
- Do I need a dark room or a warmed-up screen?
- For geometry alone, no, but a screen warmed up for 15 to 30 minutes and a dim room make dead pixels and uneven edges easier to judge when you run the other display checks.
- Can a flat panel have pincushion or barrel distortion?
- Rarely. Flat panels map pixels to a fixed matrix, so bowing and trapezoid shapes mostly appear on CRT monitors and projectors. On an LCD or OLED, suspect scaling, zoom or aspect mode first.
- How accurate is a browser-based geometry test?
- It is accurate for finding scaling, cropping and stretch, but a browser cannot measure the panel itself. Measure the circle and cells with a ruler and compare them with the calculated sizes.