AdCheckLab
for marketers
AdCheckLab
for marketers
Enter a width or a height and get the matching side for any common ratio, reduce a custom size to its ratio, and work out the black bars when landscape video goes into a vertical frame. It works for images too.
Calculate the black bars needed to place landscape or square video inside a vertical frame without stretching it.
1080×1920 is the standard upload for TikTok, Reels and Shorts. Edit at that size, or at 2160×3840 for a 4K master.
Aspect ratio alone does not guarantee safety. Test your video in the Safe Zone Checker to avoid button obstruction.
A 16:9 clip letterboxed into 9:16 fills only about a third of the screen height. Cut native 9:16 footage for vertical ad placements whenever you can.
An aspect ratio is the width of a frame divided by its height. It says nothing about sharpness: 1280 × 720 and 3840 × 2160 are both 16:9.
| Ratio | Common pixel sizes | Where it is used |
|---|---|---|
| 16:9 | 1280 × 720, 1920 × 1080, 3840 × 2160 | YouTube, connected TV, desktop video, presentations |
| 9:16 | 720 × 1280, 1080 × 1920, 2160 × 3840 | TikTok, Instagram Reels and Stories, YouTube Shorts, Snapchat |
| 1:1 | 1080 × 1080 | Square feed posts and carousel cards |
| 4:5 | 1080 × 1350 | Portrait feed posts and ads on Instagram and Facebook |
| 4:3 | 1024 × 768, 1440 × 1080 | Tablets, older TV footage, some slide templates |
| 21:9 | 2560 × 1080, 3440 × 1440 | Ultrawide monitors and cinematic looks |
| 2:3 | 1000 × 1500, 1080 × 1620 | Standard Pinterest pins |
21:9 needs a footnote: it is a marketing label, not an exact ratio. 2560 × 1080 reduces to 64:27 (2.370) and 3440 × 1440 to 43:18 (2.389), while a true 21:9 is 2.333. That is why the 21:9 preset turns 2560 wide into 1097 tall, not 1080.
The ratio only gives you the shape. Every platform also covers part of the frame with its interface, so take the exact safe zone numbers from the social and IAB specs page and the guides for TikTok safe zones and Instagram Reels safe zones. The social media video aspect ratio guide adds 4K sizes and export settings.
Write the ratio as width:height. For the height, multiply the width by the second number and divide by the first. For the width, multiply the height by the first number and divide by the second.
The calculator does this as you type, and adds the megapixel count and the orientation.
Divide both sides by their greatest common divisor. 1920 and 1080 share 120, which leaves 16:9. 1366 and 768 only share 2, which leaves 683:384, close to 16:9 but not equal (1.779 against 1.778). Choose Custom in the ratio menu, type both sides, and the calculator reduces them for you.
A calculated side is often a fraction. The calculator rounds to the nearest whole pixel, which is fine for images, but H.264 and HEVC in the usual 4:2:0 format store colour at half resolution, so both sides must be even. Many encoders reject an odd size or crop a pixel without asking.
At common video sizes, moving a side by one or two pixels changes the ratio by well under half a percent, which nobody will see. Multiples of 8 or 16 compress a little more efficiently but are not required: 1080 is not a multiple of 16, and H.264 encoders simply pad it to 1088 internally.
The letterbox panel scales the source to the full width of the target and splits the leftover height into two bars. 1920 × 1080 scaled to 1080 wide becomes 607.5 tall, rounded to 608, which leaves 656 pixels above and 656 below in a 1080 × 1920 frame. The picture then fills about a third of the screen height, so keep text inside that middle band and check it in the safe zone checker.
16:9. Both sides divide by 120, giving 16 and 9. Turned on its side, 1080 × 1920 is 9:16.
9:16 at 1080 × 1920 pixels. The ratio is only half of it: the platform interface covers the top, bottom and right edge, so check the safe zone for each platform before you place text.
At the same 1080 pixel width, 4:5 is 1350 tall against 1080 for 1:1, so it takes 25% more height on a phone screen. Square still suits carousels and placements that crop to 1:1.
Scale both sides by the same factor, so the ratio stays the same. 3840 × 2160 halved is 1920 × 1080, still 16:9. To change the ratio, crop or add bars instead of stretching.
Most delivery codecs store colour at half resolution in both directions, so an odd side cannot be split evenly. Round to the nearest even number. Images and banners have no such rule.