Aspect Ratio Calculator: Width, Height & Pixel Dimensions
Aspect Ratio Calculator. Enter a Width and Height in this aspect ratio calculator to get the simplified Aspect Ratio and its Decimal value. Use the ppi calculator to compare two monitors of different sizes and resolutions side by side for sharpness.
Interactive Tool
Find Aspect Ratio
Enter width and height to find the aspect ratio.
Find Missing Dimension
Enter an aspect ratio and one dimension to find the other.
Resize Maintaining Ratio
Resize dimensions while maintaining the aspect ratio.
Width and Height from Diagonal
Enter an aspect ratio and a screen diagonal to find the width and height.
Common Aspect Ratios
Click a ratio to load it into the Find Missing Dimension and Width and Height from Diagonal calculators above.
Enter width and height into the aspect ratio calculator to find the aspect ratio and its decimal value, or work the other way — plug in a known ratio and one dimension to solve for the other, or resize a set of dimensions while keeping the exact same proportions.
Whether you're prepping photos for a gallery, a clip for export from your editing timeline, or a web design mockup, the aspect ratio calculator tells you the exact shape of your frame. Enter a width and height in pixels to get the simplified ratio and its decimal value, or give it one new side and it fills in the missing value, so resizing images never distorts them.
How to Calculate Aspect Ratio from Width and Height
An aspect ratio is the width-to-height proportion of a rectangle: the ratio of width to height, written as W:H. Measure both sides in the same units (pixels, inches or centimeters all work), because the result has no unit. A resized image keeps its shape at any size.
Method 1: Divide Width by Height
Divide width by height. The quotient is the decimal form, written as q:1, so a shape twice as wide as it is tall is 2:1. This width:height ratio makes comparisons easy: a larger quotient always means a wider shape.
$$q = \frac{W}{H}$$Method 2: Reduce with the Greatest Common Factor
To express the ratio in whole numbers, find the greatest common factor (GCF) of the two sides, call it G, then divide both sides by it.
$$W:H = \frac{W}{G} : \frac{H}{G}$$Example Aspect Ratio Calculation
Say your laptop display is 2560 × 1600. The aspect ratio calculation works both ways:
- Divide: 2560 ÷ 1600 = 1.6, so the ratio is 1.6:1.
- Whole numbers: the largest shared factor of 2560 and 1600 is 320, and 2560 ÷ 320 = 8 while 1600 ÷ 320 = 5, giving 8:5.
Manufacturers market 8:5 as 16:10, the same shape doubled. Many productivity displays use it, while a 3840 × 2160 panel reduces to the wider 16:9.
Find a New Width or New Height with the Aspect Ratio Calculator
When you know the original size and only one target side, the tool solves the other by holding the shape fixed: Use the resolution checker to confirm your display resolution before comparing displays or running diagnostic tests.
$$H_2 = \frac{H_1}{W_1} \times W_2$$- Enter the original width and original height to lock the ratio.
- Type either a new width or a new height.
- Read the matching side and round it to the nearest whole number; the aspect ratio stays identical.
Resizing Images Without Stretching
Suppose a 5472 × 3648 photo from your camera needs a 1200-pixel-wide slot on a blog. 3648 ÷ 5472 × 1200 = 800, so the matching height is 800 pixels and the image aspect ratio stays 3:2. Force any other height and the picture gets stretched, with faces squishing sideways. For social media posts, banner ads and other digital media content, enter the platform's required ratio as the original sides, then type the width you need.
Crop or Pad When the Ratio Changes
If the target shape differs from your source image, you have two options. Crop trims the image edges to fill the new frame, best when the subject sits in the center. Pad adds black bars so nothing is lost, the usual fix when the video aspect ratio of an old clip doesn't match a modern screen.
A Projector Width-to-Height Ratio Check Before a Conference Talk
I'm presenting at a regional user group next week, and the venue's tech sheet lists the room projector as 1280 × 800 (WXGA). My deck was built at 1920 × 1080. The decision I need to make tonight: keep the deck as it is, or rebuild every slide, because the deck and projector differ in aspect ratio. The short answer the numbers give me is that the deck survives, but 10% of the screen height goes to black bars. The video resolution calculator covers common codecs and colour spaces so file size estimates reflect real-world encoding conditions.
First I enter the projector's sides, 1280 and 800. The tool reduces them by their largest shared factor, 160, to 8:5, or 1.6:1. My slides are 1.78:1, so the aspect ratios don't match. Next I lock my slide shape and type the projector's width, 1280, as the new width. The matching height comes back as 720 pixels. The projector has 800 rows, so 80 rows sit empty: 40 at the top and 40 at the bottom.
I cross-check the other way. If I scale to fill the 800-pixel height instead, the width becomes 1,422.2 pixels, about 142 more than the projector can show. That is the trap: some projector menus default to "fill", which would quietly cut 71 pixels off each side, right where my slide footers and page numbers sit.
| Projector | Native shape | Slide height at full width | Unused rows |
|---|---|---|---|
| 1280 × 800 (WXGA) | 1.6:1 | 720 | 80 (10%) |
| 1920 × 1200 (WUXGA) | 1.6:1 | 1,080 | 120 (10%) |
The rerun with a sharper projector surprised me at first: the bars grow to 120 rows, but the share stays at exactly 10%. The lost fraction depends only on the two ratios, 1 − 1.6 ÷ 1.78, not on the resolution. So a better projector won't fix this; only matching the shape will.
My call: I keep the 1.78:1 deck, because 10% letterboxing is a fair trade against rebuilding 34 slides, and I email the venue to set the projector to "fit", not "fill". The one input I'd watch in any version of this check is the scaling mode, since the aspect ratio math is only right if the display doesn't crop behind your back.
Standard Aspect Ratios for Screens, Video and Print
Most projects use a handful of standard aspect ratios. Pick the standard aspect ratio for your output, then size your output to match:
| Ratio | W ÷ H | Typical use | Example size |
|---|---|---|---|
| 16:9 | 1.78 | HD and 4K TVs, YouTube | 1920 × 1080 |
| 16:10 | 1.60 | Laptop and desktop displays | 2560 × 1600 |
| 4:3 | 1.33 | Fullscreen footage, tablets | 1024 × 768 |
| 3:2 | 1.50 | DSLR photography, print | 5472 × 3648 |
| 1:1 | 1.00 | Square feed posts | 1200 × 1200 |
| 1.85:1 | 1.85 | DCI flat projection | 1998 × 1080 |
| 2.35:1 | 2.35 | Anamorphic film | Varies by scan |
Widescreen, Ultrawide and Vertical Ratios
- 16:9 widescreen: monitors, TVs and YouTube; a 16:9 ratio calculator covers most editing jobs.
- 21:9 ultrawide: gaming monitors and panoramic desktops.
- 9:16 vertical: smartphones, TikTok and Instagram Reels.
- 1:1 square and 4:3: feed posts and older fullscreen footage.
Resolution vs. Ratio: Same Shape, Different Pixels
Resolution is the size; the ratio is the shape. A 1280 × 720 image and a 2560 × 1440 image reduce to the same ratio, so scaling between them needs no trimming. A bigger file adds detail, not a different shape.
Custom Ratio and Nearest Standard Match
Not every project fits the presets. Enter a custom ratio such as 4:5 for portrait posts or 3:1 for a header strip. The free aspect ratio calculator also shows the nearest standard: a 1366 × 768 screenshot reduces to 683:384, which sits next to the familiar 1.78:1 shape.
Cinema and IMAX Frame Ratio Formats
Theatrical delivery follows the Digital Cinema Initiatives (DCI) specs: Flat is 1.85:1 and Scope is about 2.39:1. To confirm Scope, enter 4096 × 1716 and the calculator reduces it to 1024:429, or 2.39:1. IMAX runs the other way, with a taller 1.43:1 picture, so one film can switch shape between scenes.
Frequently Asked Questions
- What does an aspect ratio like 16:9 mean?
- It is the width-to-height proportion of a frame: 16 units of width for every 9 units of height. The units don't matter, so the ratio describes the shape, not the size.
- How do I calculate aspect ratio from width and height?
- Divide the width by the height for the decimal form (for example 1.6:1), or divide both numbers by their greatest common factor to get whole numbers (2560 × 1600 becomes 8:5, also written 16:10).
- How do I find a new height when resizing an image?
- Divide the original height by the original width and multiply by the new width. Choose Resize, enter the original size and the new width, and the calculator returns the matching height so the image is not stretched.
- What is the difference between aspect ratio and resolution?
- Resolution is the size in pixels, such as 1920 × 1080. The aspect ratio is the shape. Many resolutions share one ratio: 1280 × 720 and 3840 × 2160 are both 16:9.
- Should I crop or pad when the aspect ratio doesn't match?
- Crop when the subject is in the middle and you can lose the edges. Pad with black bars when every part of the picture must stay visible.
- Can I use a custom aspect ratio?
- Yes. Set the preset to Custom and type any ratio width and height, such as 4:5 for portrait posts or 3:1 for a banner. The calculator also shows the nearest standard ratio.
- Does it matter which units I use?
- No, as long as width and height use the same units. Pixels, inches, centimeters and millimeters all give the same aspect ratio; the unit only labels the width, height and diagonal results.