How to Measure Monitor Size

What You'll Need

Before you begin measuring your monitor, gather these tools:

• Measuring tape or ruler: Preferably one that shows both inches and centimeters
• Pen and paper: For recording your measurements
• Calculator: Optional, for converting units or calculating dimensions
• Clean cloth: To wipe the screen if needed for better visibility

Pro tip: A flexible measuring tape works better than a rigid ruler, especially for curved screens or measuring diagonals on larger monitors.

Method 1: Measuring Diagonal Size (Standard Method)

Monitor size is traditionally measured diagonally from corner to corner. This is the measurement manufacturers use when advertising screen size (24", 27", 32", etc.).

Step-by-Step Instructions

1. Turn off your monitor: This makes the screen edges more visible. A black screen shows exactly where the display area ends.
2. Identify the visible screen area: Look for where the actual display ends and the bezel (plastic frame) begins. You should only measure the lit display area, not the frame.
3. Choose your starting corner: It doesn't matter which corner you start from. Most people find bottom-left to top-right easiest.
4. Place the measuring tape: Position the tape measure's zero mark at the very corner of the visible display area (not the outer edge of the bezel).
5. Extend to opposite corner: Stretch the tape diagonally across the screen to the opposite corner. Keep it taut and straight.
6. Read the measurement: Note where the tape meets the opposite corner. This is your diagonal screen size.
7. Record in inches: Most screen sizes are expressed in inches. If you measured in centimeters, divide by 2.54 to convert.

Common Mistakes to Avoid

• Including the bezel: Only measure the screen itself, not the plastic frame
• Measuring horizontally or vertically: Screen size is always diagonal
• Letting the tape sag: Keep it taut for an accurate measurement
• Rounding too much: Be precise to the nearest tenth of an inch (e.g., 27.2")

Example Measurements

Method 2: Measuring Width and Height

Sometimes you need the exact width and height measurements, not just the diagonal. This is useful for:

• Calculating screen area
• Checking if a monitor fits a specific space
• Comparing aspect ratios
• Ordering screen protectors or privacy filters

How to Measure Width

1. Place your measuring tape at the left edge of the visible screen
2. Extend it horizontally across to the right edge
3. Keep the tape parallel to the top and bottom edges
4. Record the measurement to the nearest 0.1 inch

How to Measure Height

1. Place your measuring tape at the bottom edge of the visible screen
2. Extend it vertically to the top edge
3. Keep the tape parallel to the left and right edges
4. Record the measurement to the nearest 0.1 inch

Common Screen Dimensions by Diagonal Size

For standard 16:9 aspect ratio monitors:

Method 3: Using Manufacturer Specifications

If you don't have a measuring tape handy, you can look up your monitor's exact specifications:

Finding Your Model Number

1. Check the back of the monitor: There's usually a sticker with the model number
2. Look at the front bezel: Some monitors have the model printed near the power button
3. Check your purchase receipt or box: The model number is always listed
4. Use system settings: On Windows, go to Settings → System → Display → Advanced display settings

Looking Up Specifications Online

Once you have the model number (e.g., "Dell U2723DE" or "LG 27UK850"):

1. Search "[model number] specifications" in Google
2. Visit the manufacturer's official website
3. Look for "Screen Size" or "Display Diagonal"
4. Also check "Active Display Area" for exact dimensions

Note: Manufacturer specifications sometimes round measurements. A monitor advertised as "27 inches" might actually be 27.2" or 26.9" diagonally.

Calculating Dimensions from Diagonal and Aspect Ratio

If you know your diagonal size and aspect ratio, you can calculate width and height mathematically.

For 16:9 Aspect Ratio (Most Common)

• Width: Diagonal × 0.8716
• Height: Diagonal × 0.4903

Example for 27" monitor:

• Width: 27 × 0.8716 = 23.5 inches
• Height: 27 × 0.4903 = 13.2 inches

For 16:10 Aspect Ratio

• Width: Diagonal × 0.8514
• Height: Diagonal × 0.5321

For 21:9 Ultrawide

• Width: Diagonal × 0.9225
• Height: Diagonal × 0.3857

For 4:3 Aspect Ratio (Older Monitors)

• Width: Diagonal × 0.8
• Height: Diagonal × 0.6

Calculating Screen Area

Screen area is useful for comparing how much visual space different monitors provide.

Formula

Screen Area = Width × Height

Examples

Interesting comparison: A 34" ultrawide monitor (21:9) has about the same screen area as a 27" standard monitor (16:9) — just arranged differently!

Special Cases: Curved and Ultrawide Monitors

Measuring Curved Monitors

Curved monitors require special attention:

1. Use a flexible measuring tape: Rigid rulers won't work well
2. Follow the curve: Let the tape curve naturally along the screen surface
3. For diagonal: Measure from corner to corner along the curve
4. For width: Measure the actual curved distance, not straight across

Note: Manufacturer specs for curved monitors usually give the "flat equivalent" diagonal measurement, not the actual curved distance.

Ultrawide Monitors

Ultrawide monitors (21:9 or 32:9 aspect ratios) are wider than standard monitors with the same diagonal:

• 34" ultrawide ≈ width of 40" standard monitor, but shorter height
• 49" super ultrawide (32:9) ≈ two 27" monitors side by side

Method 4: Using Our DPI Calculator

The easiest and most accurate method: Use our Screen DPI Calculator with credit card calibration.

Why This Method is Best

• No physical measuring needed: Uses a standard credit card as reference
• Extremely accurate: Within 1-2% of actual size
• Automatic calculations: Gives you diagonal, width, height, and DPI
• Works on any screen: Desktop, laptop, tablet

How It Works

1. Visit our DPI Calculator
2. Select "Credit Card Calibration"
3. Adjust the on-screen rectangle to match your physical credit card
4. Click "Calibrate"
5. Get instant results with all dimensions

Why Accurate Measurements Matter

For Desk Setup Planning

Knowing exact dimensions helps you:

• Choose the right monitor arm or stand
• Ensure the monitor fits your desk space
• Plan multi-monitor setups accurately
• Maintain proper viewing distance (1.5× to 2× diagonal is recommended)

For Accessory Shopping

Accurate measurements ensure proper fit for:

• Screen protectors
• Privacy filters
• Monitor hoods (for photo/video editing)
• Carrying cases or covers

For Comparing Monitors

Screen area gives a better comparison than diagonal alone:

• A 34" ultrawide has less area than a 32" standard monitor
• Two 24" monitors provide 492 sq in vs. 438 sq in for one 32" monitor
• Aspect ratio significantly affects usable space

Tips for Accurate Measurements

Do's

• ✓ Use a flexible measuring tape for best results
• ✓ Measure the visible screen area only, not the bezel
• ✓ Take measurements with the screen turned off for visibility
• ✓ Measure twice to verify accuracy
• ✓ Record measurements immediately to avoid forgetting
• ✓ Use the metric system if you're more comfortable, then convert

Don'ts

• ✗ Don't include the bezel/frame in your measurement
• ✗ Don't measure horizontally or vertically when you need diagonal
• ✗ Don't rely on rounded manufacturer specs if precision matters
• ✗ Don't forget to account for screen curvature on curved monitors
• ✗ Don't use damaged or stretched measuring tapes

Quick Reference: Standard Monitor Sizes

Troubleshooting Common Issues

My measurement doesn't match the advertised size

This is normal. Manufacturers round to the nearest whole number. A "27-inch" monitor might actually be 27.2" or 26.9" when measured precisely.

I can't see where the screen ends

Solution: Turn off the monitor completely. The black screen makes the border between display and bezel much more visible.

My curved monitor measurement seems wrong

Remember: Curved monitors are measured by their "flat equivalent" diagonal, not the actual curved surface distance. Your measurement might be longer if you followed the curve.

I don't have a measuring tape

Alternatives:

• Use a piece of string, then measure the string against a ruler
• Check your monitor's model number and look up specs online
• Use our DPI Calculator with credit card calibration (no measuring needed!)

Conclusion

Measuring your monitor size accurately is straightforward once you know the proper technique. Whether you use a measuring tape, manufacturer specs, or our credit card calibration method, you now have multiple ways to determine your exact screen dimensions.

For the quickest and most accurate results without any physical measuring, try our Screen DPI Calculator — it automatically calculates all dimensions and gives you your screen's pixel density as a bonus!