📺 Video & Image Resolution Tool

Aspect Ratio & Resolution Calculator

Calculate aspect ratios (16:9, 4:3, 21:9, 1:1, 9:16), scale pixel resolutions, and calculate missing dimensions for videos, photos, and displays.

Common Ratio Presets:

⚙️ Dimension Input & Target Scaling

Original Width (px / in)

Original Height (px / in)

New Width (Optional)

New Height (Optional)

Proportional Scaling Formula

1920 / 120 : 1080 / 120 = 16:9

New Height = 1280 × (1080 / 1920) = 720 px

📊 Calculated Ratio & Scaled Resolution Live Proportional Calculations

Simplified Aspect Ratio

16:9

Simplified

Decimal Aspect Ratio

1.78:1

Decimal

Scaled Height (for New Width)

720 px

Target Height

Total Megapixels / Resolution

2.07 MP

2,073,600 Px

Interactive Aspect Ratio Canvas Stage

1920 x 1080 px (16:9)

Scaled Proportional Rectangle Box

📖 Popular Display Resolutions & Aspect Ratios Chart

Resolution (Px)	Aspect Ratio	Common Use Cases
1920 × 1080 (FHD)	16:9	Standard HD TV, YouTube Videos, Monitors
3840 × 2160 (4K UHD)	16:9	4K Televisions, Streaming, Displays
1080 × 1920 (Vertical)	9:16	TikTok, Instagram Reels, YouTube Shorts
2560 × 1080 (Ultrawide)	21:9	Ultrawide Gaming Monitors, Cinematic Video

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Auto Screen Calibration

OnlineRulerAI auto-detects your screen PPI database (250+ devices) to display 100% 1:1 real-world dimensions instantly.

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Credit Card & Coin Fit

Match any standard credit card (85.60 mm), bank card, or coin against your display for pinpoint physical accuracy.

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Visual Caliper & Guidelines

Drop reference guidelines, track cursor crosshairs, or drag rulers across screen edges in inches, cm, mm, and px.

Free Online Ruler — Measure in Inches, cm & mm at Actual Size

Free online ruler calibrated to actual size in inches, cm, and mm without downloads. Features auto screen detection, credit card calibration, protractor, and visual calipers.

Calibrate for 100% Physical Accuracy

Click Calibrate to auto-detect your screen or match a physical credit card, banknote, or monitor diagonal.

1. Device Database: Auto-detect screen PPI database (250+ devices).
2. Screen Diagonal: Calculate exact PPI from monitor diagonal in inches.
3. Credit Card: Match physical credit card (85.60 mm) to on-screen slider.
4. Banknote & Object: Compare physical banknote or coin against screen.

Select Your Measurement Unit

Switch between Centimeters (cm), Millimeters (mm), Inches (inch), Pixels (px), Points (pt), Picas, Feet, and Yards.

Place & Measure Objects

Place objects along screen edge rulers, drag visual caliper, or click Guidelines/Crosshair to measure in real time.

❓ Frequently Asked Questions (FAQ)

Click any question below to expand the detailed answer.

Q1. Can I use my phone as a ruler?

Yes! OnlineRulerAI turns any smartphone (iPhone, Android, Samsung, Pixel) into a 1:1 actual size digital ruler. You can calibrate your mobile display using a standard credit card (85.60 mm) or auto-detect your device model to measure physical objects directly on your screen.

Q2. Is there a ruler online?

Yes, OnlineRulerAI provides a free online ruler calibrated to actual real-world physical dimensions. It displays 12 inch, 30 cm, and millimeter scale lines on your monitor, tablet, or mobile phone screen without downloading any app.

Q3. How to identify 1 inch?

One inch equals exactly 2.54 centimeters or 25.4 millimeters. On an actual size online ruler, 1 inch is demarcated by the longest tick mark labeled with a '1″' symbol.

Q4. How to measure cm online?

Select the 'cm' unit button on OnlineRulerAI. Place your physical object flat against your screen aligned with the zero line (0 cm), and read the corresponding major mark.

Q5. Can a smartphone measure?

Yes, via camera AR apps or directly on screen using OnlineRulerAI browser tools for small items up to 15 cm with millimeter precision.

Q6. Can I use my camera as a ruler?

Yes! Camera ruler applications use AR camera alignment to measure room dimensions, furniture, and larger physical items in real-time.

Q7. Can we measure online?

Absolutely. You can measure physical items directly on your computer or mobile screen using OnlineRulerAI's free web tools.

Q8. How to read a ruler online?

Align one end of your object with the '0' mark. In cm mode: numbered tick marks are centimeters; smallest ticks are millimeters. In inch mode: numbered ticks are full inches.

Q9. How to view or add a ruler in Word Online?

In Microsoft Word Online, click on the 'View' tab in the top ribbon and check the 'Ruler' box.

Q10. How to show a ruler in PowerPoint Online?

In Microsoft PowerPoint Online, navigate to the 'View' tab and check the 'Ruler' box.

Q11. How to use an online ruler?

Open OnlineRulerAI in your browser, click 'Calibrate' to adjust your screen PPI with a credit card or device model, and lay your object flat on the screen to measure.

How to Calculate Aspect Ratio and Scale Resolutions

Aspect ratio describes the proportional relationship between an image or screen's width and height. Simplify the fraction Width/Height by GCD.

Proportional Scaling Formulas

Aspect Ratio Reduction

Ratio = (Width / GCD) : (Height / GCD)

Height Resizing Formula

New Height = New Width × (Original Height / Original Width)

Frequently Asked Questions (FAQ)

What is 1920x1080 in aspect ratio?

1920x1080 resolution is exactly 16:9 widescreen aspect ratio.

How do you resize an image while keeping aspect ratio?

Multiply the new width by the ratio of (Height / Width) to find the proportional new height.