Aspect ratio calculator
Work out the missing width or height for 16:9, 9:16, 4:5, 1:1 or any ratio, find the ratio of a size or file, and see what cropping or letterboxing costs.
Runs in this tab. Nothing you paste or drop is uploaded.
Find the missing size
Change either side and the other follows the ratio. Exact height for 1920 px wide: 1080.00 px.
Platform sizes
16:9 · 1.778 · 2.07 MP · landscape
What ratio is this?
Or drop an image or video here, or . Only its size is read; nothing is uploaded.
- Exact ratio
- 16:9
- Closest standard
- 16:9exact
- As a number
- 1.778
- Shape
- landscape
16:9 is used for: YouTube, TV, most cameras.
Fit it into another ratio
Crop (fill)
608 × 1080
Cut 656 px from each side. You lose 68% of the picture.
Letterbox (fit)
1920 × 3413
Add 1167 px bars at the top and bottom. Bars fill 68% of the frame.
Keep going
- EditSRT to VTT converter (and VTT to SRT)Paste or drop a subtitle file and get the other format back. Runs in your browser; nothing is uploaded.
- PublishSafe zone checker for TikTok, Reels and ShortsDrop a frame or a short clip to see where TikTok, Instagram Reels and YouTube Shorts put their buttons, captions and username over your video.
- ScriptSpeech time calculator: words to minutesPaste a script, speech or voiceover to see how long it takes to read at 130, 150 or 170 words per minute, with word and character counts.
How it works
An aspect ratio is width divided by height, written as two numbers: 16:9 means 16 units wide for every 9 tall. Keeping the ratio when you resize is what stops a picture from looking stretched or squashed.
Find the missing size. Pick or type a ratio, then type either the width or the height; the other side is worked out as width × (b ÷ a) or height × (a ÷ b) and rounded to whole pixels. Tick "even numbers" for video: most encoders (H.264, H.265) need even dimensions, so 1000 wide at 16:9 becomes 1000 × 562 instead of 563. The exact unrounded value is shown too. The platform buttons load the usual upload sizes, such as 1920 × 1080 for YouTube and 1080 × 1920 for Shorts, Reels and TikTok.
What ratio is this? Type a width and height, or drop an image or video to read its size. The exact ratio is the size divided by its greatest common divisor (1920 × 1080 → 16:9). Sizes that do not reduce neatly, like 1366 × 768 (683:384), also show the closest standard ratio and how far off they are.
Fit it into another ratio. Choose a target such as 9:16 and you get both options side by side:
- Crop (fill): the largest rectangle of the target ratio that fits inside your picture, centred, and how much is cut away. A 1920 × 1080 video cropped to 9:16 keeps 608 × 1080 and loses 68%.
- Letterbox (fit): the smallest canvas of the target ratio that holds the whole picture, and the size of the bars. The same video letterboxed to 9:16 needs a 1920 × 3413 canvas with 1167 px bars top and bottom.
Files are read only for their width and height, inside your browser. Nothing is uploaded.
When to use it
Whenever a size has to match a shape.
- Exporting the same edit for YouTube (16:9), Shorts, Reels and TikTok (9:16) and Instagram posts (4:5).
- Sizing thumbnails (1280 × 720), link preview images (1200 × 628, about 1.91:1) and square posts.
- Checking whether a camera or screen recording is really 16:9 before you edit.
- Deciding between cropping a landscape clip to vertical and letterboxing it.
- Resizing an image for a page or slide without it looking stretched.
For vertical video, check what the app interface covers with the safe zone checker after you resize.
Questions
How do I calculate an aspect ratio?
Divide the width and height by their greatest common divisor. 1920 and 1080 share 120, so 1920 × 1080 is 16:9. Type the size into "What ratio is this?" and the tool does it, along with the closest standard ratio.
What size is 16:9?
Any size where width ÷ height = 1.778. Common ones are 1280 × 720 (720p), 1920 × 1080 (1080p), 2560 × 1440 (1440p) and 3840 × 2160 (4K). Choose 16:9 and type a width to get the matching height.
What size is 9:16 for Shorts, Reels and TikTok?
1080 × 1920 pixels. It is 16:9 turned on its side. Smaller exports like 720 × 1280 are the same shape but look softer.
What is the difference between cropping and letterboxing?
Cropping fills the new shape and cuts off whatever does not fit. Letterboxing keeps the whole picture and adds bars (black, blurred or coloured) to fill the gap. The tool shows the exact sizes and how much is lost or added for each.
Why round to even numbers?
Most video encoders, including H.264 and H.265 with common settings, require the width and height to be even. An odd size can fail to export or get a one-pixel border, so the option rounds to the nearest even number.
Is my image or video uploaded?
No. Only its width and height are read, inside your browser, and the file is released straight away. The sizes you type are remembered on this device and kept in the page link so you can share a setup.
Last tested: