Resolution & Scale Calculator
Give it an aspect ratio and one edge — width, height or the long side — and it returns exact pixel dimensions. Or start from a resolution you already have and scale it by percentage. Both round to even numbers by default, because that is what H.264 and H.265 expect.
Calculate dimensions
H.264 and H.265 store colour at half resolution on both axes, so they expect even numbers. Leave this on unless you know your target accepts odd sizes.
Common delivery sizes
| Name | Resolution | Ratio | Megapixels | Typical use |
|---|---|---|---|---|
| 4K UHD | 3840 × 2160 | 16:9 | 8.29 | 16:9 — YouTube 4K and most UHD delivery. |
| 1440p QHD | 2560 × 1440 | 16:9 | 3.69 | 16:9 — a common master size for high-motion uploads. |
| 1080p FHD | 1920 × 1080 | 16:9 | 2.07 | 16:9 — the default for nearly everything. |
| 720p HD | 1280 × 720 | 16:9 | 0.92 | 16:9 — small proxies and older embeds. |
| Vertical 1080 | 1080 × 1920 | 9:16 | 2.07 | 9:16 — Reels, Shorts, TikTok and Stories. |
| Portrait feed | 1080 × 1350 | 4:5 | 1.46 | 4:5 — tallest the Instagram feed shows uncropped. |
| Square | 1080 × 1080 | 1:1 | 1.17 | 1:1 — feed posts and many ad placements. |
| DCI 2K flat | 1998 × 1080 | 1.85:1 | 2.16 | 1.85:1 — theatrical flat container. |
| DCI 2K scope | 2048 × 858 | 2.39:1 | 1.76 | 2.39:1 — theatrical scope container. |
What a percentage scale actually costs
| Scale | Resolution | Megapixels | Share of the pixels |
|---|---|---|---|
| 25% | 960 × 540 | 0.52 | 6.3% |
| 50% | 1920 × 1080 | 2.07 | 25.0% |
| 75% | 2880 × 1620 | 4.67 | 56.3% |
| 150% | 5760 × 3240 | 18.66 | 225.0% |
| 200% | 7680 × 4320 | 33.18 | 400.0% |
A percentage applies to each axis, so the pixel count moves with its square. 1920 × 1080 at 50% is 960 × 540 — 25% of the pixels, not half. That square is the reason a small drop in resolution buys such a large drop in encode time and file size.
The arithmetic
A resolution is a ratio plus a size. Fix the ratio, pin one edge, and the other edge follows:
height = width ÷ ratio · width = height × ratio
- 1920 × 1080: 1920 ÷ 1.7778 = 1080, giving 16:9 at 2.07 megapixels. The same ratio at 3840 × 2160 is still 16:9 — four times the pixels, identical shape.
- Vertical delivery: pin the long edge of a 9:16 frame to 1920 and you get 1080 × 1920 — the same pixel count as HD, rotated.
- Scope inside HD: a 2.39:1 picture at 1920 pixels wide is 1920 × 804. Anything taller than 804 pixels is letterbox, not picture.
Even-pixel rounding nudges these results by up to one pixel per axis. That is deliberate: an encoder that rejects an odd dimension costs more than a pixel of accuracy does. The calculator flags the ratio drift when rounding moves the shape enough to matter.
Frequently asked questions
How do I scale a video without distorting it?
Change one dimension and let the other follow the aspect ratio, rather than typing both by hand. Pin the width, the height or the long edge, and the calculator derives the rest. If you set both independently you are changing the shape, not the size, and the picture stretches.
Why do video dimensions have to be even numbers?
H.264 and H.265 store colour at half resolution on both axes — 4:2:0 chroma subsampling — so each pair of pixels needs a partner. An odd width or height leaves a half-sample the encoder cannot represent, so it either refuses the file or silently pads it. Leave 'force even dimensions' on for anything you intend to encode.
What is 1920 × 1080 scaled to 50 percent?
960 × 540, which is still 16:9. Note that halving each axis leaves a quarter of the pixels, not half: 2.07 megapixels becomes 0.52. That is why a 50 percent scale cuts encode time and file size far more than the percentage suggests.
What resolution is 9:16 vertical video?
1080 × 1920 is the standard for Reels, Shorts, TikTok and Stories. It is the same pixel count as 1920 × 1080, just turned on its side. Pick the 9:16 preset and pin the long edge to 1920 to get there.
How do I work out the aspect ratio of a resolution I already have?
Divide width by height and reduce it. Switch to 'Scale a source', type your dimensions, and the readout names the ratio — 1920 × 1080 reduces to 16:9, 1080 × 1350 to 4:5. Sizes that do not reduce to small whole numbers, like the DCI cinema containers, are shown in decimal form such as 1.85:1 instead.
Does scaling a video up improve its quality?
No. Scaling up invents pixels by interpolating between the ones you have, so the result is larger and softer, never more detailed. Upscaling is worth doing only to meet a delivery spec that demands a minimum resolution — and in that case encode at the higher size from the original master rather than scaling an already-compressed export.