Aspect Ratio Calculator
Get the aspect ratio of any width and height, or work out the missing side for a ratio like 16:9 or 4:5 — then open that exact size in the image stretcher.
Find the ratio of a size
Enter an image's width and height in pixels to get its aspect ratio.
Aspect ratio16:9
- Decimal
- 1.78:1
- Shape
- Landscape
Find a missing width or height
Pick a ratio, enter the side you know, and get the other one in whole pixels.
Common ratios
16:9 at this width1600 × 900px
How aspect ratio is worked out
An aspect ratio is a size with the scale taken out. Divide the width and height by the largest number that goes into both, and what is left is the ratio: 1920 and 1080 both divide by 120, leaving 16:9.
Going the other way, the missing side is the known side multiplied across the ratio. For a 4:5 image 1080px wide, the height is 1080 × 5 ÷ 4 = 1350px.
A ratio says nothing about file size or sharpness — 1280 × 720 and 3840 × 2160 are both 16:9. If an upload form gives you a limit in KB rather than pixels, use Resize Image to KB instead.
Common ratios and the sizes that use them
| Ratio | Example sizes (px) | Typically used for |
|---|---|---|
| 1:1 | 1080 × 1080, 1200 × 1200 | Square posts, profile images |
| 4:5 | 1080 × 1350 | Portrait posts |
| 3:2 | 1200 × 800, 6000 × 4000 | Most camera photos |
| 4:3 | 1024 × 768, 1600 × 1200 | Tablets, older screens and cameras |
| 16:9 | 1280 × 720, 1920 × 1080, 3840 × 2160 | Video, presentations, most screens |
| 9:16 | 1080 × 1920 | Stories, reels, vertical video |
Frequently asked questions
What is the aspect ratio of 1920 × 1080?
16:9. Both numbers divide by 120, which leaves 16 and 9. The same is true of 1280 × 720, 2560 × 1440 and 3840 × 2160 — they are different sizes with the same shape.
How do I calculate the height for a 16:9 image?
Divide the width by 16 and multiply by 9. A 1600px-wide 16:9 image is 1600 ÷ 16 × 9 = 900px tall.
In the calculator, pick 16:9, leave the known side on Width, and type your width — the height appears straight away.
Why isn't my result exactly the ratio I picked?
Images can only be a whole number of pixels, so the missing side is rounded. At 4:5, a width of 1001px works out to 1251.25px, which becomes 1251. The calculator tells you when rounding happened and what the exact figure was.
Choosing a known side that divides evenly by the ratio — for 16:9, any width that is a multiple of 16 — avoids rounding altogether.
What does it mean when the ratio comes out as something like 683:384?
That size doesn't reduce to small numbers. 1366 × 768, a common laptop resolution, is exactly 683:384 — which is so close to 16:9 that it is sold as 16:9. When a size is within 1% of a common ratio, the calculator shows that ratio too.
How do I change an image to a different aspect ratio?
This calculator only does the arithmetic — it never opens a file. Once you have the size, select Open this size in the Image Stretcher and choose an image.
There you decide how the picture meets the new shape: Stretch distorts it to fill, Fit keeps the whole image and pads the gaps, and Crop fills the frame by trimming the edges.
Is 4:5 the same as 1080 × 1350?
Yes. 1080 × 1350 reduces to 4:5 — both numbers divide by 270. It is the usual size for a portrait post; 1080 × 1080 is the square 1:1 equivalent.