Enter your source resolution and get the exact pixel dimensions for 9:16, 1:1, 4:5 and 16:9 — plus the percentage of the frame each crop discards, so you know what you are losing before you export.
Unlimited — runs in your browser, nothing is uploaded
How It Works
Type the width and height of your original footage — 1920×1080, 3840×2160, or whatever your camera or screen recorder produced.
Every common short-form ratio is calculated at once, at the largest size your source can fill without upscaling.
Each ratio shows what percentage of the original frame is cut away, so you can tell a safe reframe from one that will cut off half your subject.
Aspect ratio is the relationship between a video's width and its height, written as two numbers — 16:9 is a landscape YouTube video, 9:16 is a full-screen vertical TikTok, Reel or Short. The ratio is not the resolution: 1280×720 and 1920×1080 are both 16:9, they just contain different numbers of pixels.
The problem this calculator solves is that converting between ratios is subtractive. Turning a 1920×1080 landscape video into 9:16 does not stretch it — it crops away the sides, and the arithmetic for how much gets cut is not obvious in your head. A 16:9 source reframed to 9:16 loses roughly 68% of its pixels. That is not a rounding error; it is most of your shot.
So this tool answers two questions at once: what exact width and height should I export at, and how much of my frame am I giving up to get there. Both run entirely in your browser — no upload, no account, no limit.
Why Use This Tool
9:16 for TikTok, Reels and Shorts. 1:1 for feed posts. 4:5 for Instagram portrait. 16:9 for YouTube and LinkedIn.
See exactly what percentage of the source frame each target ratio throws away before you commit to it.
Pure arithmetic in your browser. Your footage never leaves your machine because it never needs to.
Results are rounded to even numbers, because H.264 and H.265 encoders reject odd pixel dimensions on chroma-subsampled video.
Check your export settings from your phone while you are still in the edit.
Targets are capped at what your source can actually fill, so the calculator never suggests a size that would soften your footage.
Reference
The ratio each platform renders full-screen. Anything else gets letterboxed, pillarboxed, or cropped by the platform itself.
9:16 at 1080×1920. All three platforms render 9:16 full-screen on a phone. Anything wider gets bars added or is cropped by the platform without asking you.
About 68% of the pixel area if you crop rather than pad. A 1920×1080 frame becomes roughly 608×1080 of usable width — which is why the subject has to be re-centred rather than simply cut down the middle.
Related but not identical. Aspect ratio is the shape of the frame; resolution is how many pixels fill that shape. This tool gives you both — the target ratio and the largest resolution your source can fill at that ratio without upscaling.
H.264 and H.265 encode colour at half resolution horizontally and vertically (4:2:0 chroma subsampling), so both dimensions must be divisible by 2. An odd number makes most encoders error out or silently round anyway.
You can upload it, but it will not fill the screen — TikTok will letterbox it. 4:5 is an Instagram and Facebook feed ratio. Use 9:16 for anything meant to be watched full-screen.
No. You type two numbers and it does arithmetic. There is no upload field, no file is read, and nothing is sent to a server.
Knowing you need 1080×1920 is the easy part. Cropping an hour of footage to it — and keeping the speaker inside the frame while they move — is the part that takes an afternoon per video. ShortsHero tracks the speaker frame by frame and reframes every clip automatically.
Reframe a video freeFree to start · No credit card required
Keep Going
Crop video online free. Drag a crop box over your footage, snap it to 9:16, 1:1, 4:5 or 16:9 for TikTok, Reels and Shorts, and export — no watermark, no sign-up.
Enter a video duration and see instantly which platforms accept it, which will reject it, and how much you need to cut. Current limits for every major platform.
Estimate video file size from bitrate, resolution and duration before you export. Checks the result against TikTok's 287.6MB upload cap. Free and instant.
Turn landscape footage into 9:16 without cropping. Fills the top and bottom with a blurred, zoomed copy of your own frame — free, no watermark, no sign-up.
Your source is 1920×1080 — an aspect ratio of 16:9.
9:16 606×1080
TikTok · Reels · Shorts
68.4%
frame lost
4:5 864×1080
Instagram feed portrait
55.0%
frame lost
1:1 1080×1080
Square feed post
43.8%
frame lost
16:9 1920×1080
YouTube · LinkedIn
0.0%
frame lost
Dimensions are the largest box of each ratio that fits inside your source, so nothing is upscaled, and both numbers are rounded down to even values because H.264 and H.265 reject odd pixel dimensions. Crop loss is measured by area — which is why 16:9 to 9:16 costs far more than the width difference alone suggests.