Set a ratio, type the size you need, and the missing width or height fills in instantly — with preset chips and common resolutions for 16:9, 9:16, 4:3, 3:2, 1:1, 4:5, 21:9 and 2.39:1.
16:9 — widescreen video (YouTube, HD/4K)
Everything runs locally in your browser. Nothing is uploaded to any server — close the tab and your files are gone.
Type W1 and H1 — your original size, or a plain ratio like 16 and 9 — or click a preset chip below to fill them in.
Fill in W2 or H2. The other one recalculates instantly to keep the exact same ratio as W1:H1.
The simplified ratio and closest standard name update live, so you can confirm exactly what ratio you’re working with.
Copy W2 × H2 for the new size, or grab any row from the common sizes table once a standard ratio is detected. Feed pieces that have to line up next to each other are a ratio problem before they are a cropping one — the Instagram grid guide works one through end to end.
A ratio is a multiplier and nothing more: lock one side, multiply, and the other side follows. That is the whole of what the solver above does. The two middle columns apply each multiplier to a 1080 px side so you can sanity-check a size at a glance, and the last column is the context that decides which row you want.
| Ratio | W ÷ H | Height at 1080 px wide | Width at 1080 px tall | Reach for it when |
|---|---|---|---|---|
| 16:9 | 1.78 | 607.5 px | 1920 px | Landscape video, screen recordings and webinar exports — the shape most players and monitors assume when a brief does not say otherwise. |
| 9:16 | 0.56 | 1920 px | 607.5 px | Anything meant to fill a phone held upright: vertical video, full-bleed story graphics, vertical ad placements. |
| 4:3 | 1.33 | 810 px | 1440 px | Scans, older camera files, and slide decks built for projectors or meeting-room screens that would otherwise show side bars. |
| 3:2 | 1.5 | 720 px | 1620 px | Photography straight out of most cameras, and the ratio to hold on to when a print should come from an uncropped frame. |
| 1:1 | 1 | 1080 px | 1080 px | Square feed posts, avatars and product tiles in a listing grid — the shape that survives being cropped by almost any layout. |
| 4:5 | 0.8 | 1350 px | 864 px | Portrait feed posts, where the extra height buys more screen space per post than a square without the platform trimming it back. |
| 21:9 | 2.33 | 462.9 px | 2520 px | Ultrawide monitor wallpapers, and letterboxed banners that run the full width of a page above the fold. |
| 2.39:1 | 2.39 | 451.9 px | 2581.2 px | Cinema-style exports, title cards and trailers, where the unusual width is the effect you are after. |
The two size columns are the exact multiplier applied to 1080 px, printed the way the calculator prints it: a whole number where the arithmetic lands on one, a single decimal where it does not. 1080 px of 16:9 really is 607.5 px tall, and quietly rounding that to 608 is a different ratio.
Keeping a ratio is arithmetic. Changing one is a decision: pixels have to be thrown away or added, and the only real question is which of those you can afford.
Cropping keeps full resolution and loses the edges. Taking a 1920 × 1080 frame to 9:16 means keeping a strip 607.5 px wide out of 1920 — under a third of the width — so it only works when the subject already sits inside that strip. Work the strip out before you commit: lock the height, read the width the calculator returns, and check what falls outside it.
Padding keeps every pixel and spends screen space instead. That same 1920 × 1080 frame placed full-width into a 1080 × 1920 vertical canvas occupies 1080 × 607.5 px — about a third of the height — leaving roughly 656 px of empty bar above and below. That is a lot of canvas to leave blank, which is why vertical edits usually fill it with a caption or a second element rather than flat colour.
Some changes are not a crop at all. A 2560 × 1080 ultrawide banner cropped to a square keeps 1080 px of its 2560 px width — 42 per cent — so whatever lived at the left and right ends is simply gone, and no amount of repositioning brings it back. When the layout depends on that width, laying the elements out again at the new ratio is faster than hunting for a crop that works.
The solver is two numbers in and one number out. What makes it useful is knowing which two numbers to put in — here are the four cases that come up most.
Put the original size into W1 and H1, type the required width into W2, and H2 lands on the only height that keeps the file undistorted. If the original is already a standard shape, you can skip a step: a 1600 px width at 16:9 is 900 px tall, at 4:5 it is 2000 px tall. The 16:9 calculator has the ratio pre-filled along with the common resolutions that go with it.
This is the crop-or-pad decision above, with numbers attached. Set the ratio to 9:16, type 1080 into W2, and H2 confirms the 1920 px canvas you are aiming at; the question left is whether the subject survives a 607.5 px-wide crop of the original frame or needs bars instead. The 9:16 calculator lists the sizes that pair with it, so you can pick the export resolution in the same pass.
A splitter divides a source into exact pixel tiles, so square tiles only ever come out of a square source. Set W1:H1 to 1:1, type 3240 into W2 — nine 1080 px tiles across three columns — and H2 confirms 3240 before you crop anything. Then hand the finished square to the Instagram grid maker, which cuts it 3×3 without adding a crop of its own.
Ratio and resolution are separate questions, and mixing them is what produces surprise white margins. Settle the shape first: a 3:2 photo printed 210 mm wide needs 140 mm of height, whatever the DPI. Then convert with the mm to px converter — at 300 DPI that page comes to roughly 2480 × 1654 px, and if your file is smaller than that, the ratio was never the problem.
Keep width and height in the same ratio as the original — stretching either one on its own is what causes distortion. Enter your original size as W1:H1, then type your target width or height into W2 or H2; the other value locks to the same ratio automatically, so nothing gets stretched or squashed.
16:9 is the standard widescreen ratio for YouTube, most monitors and TVs, and HD/4K video — 1280×720, 1920×1080 and 3840×2160 are all 16:9. It’s the default for horizontal video on nearly every platform.
9:16 is full-screen vertical video for Reels and Stories (1080×1920). 4:5 is the tallest ratio the main feed displays without cropping (1080×1350). 1:1 is a square feed post (1080×1080). Anything taller than 4:5 gets cropped down when it’s published to the feed.
Instagram caps feed posts at a 4:5 ratio — anything taller is cropped down to 4:5 on publish. 1080×1350 is the largest vertical canvas that shows in full without any cropping.
Real export sizes are always whole pixels, so dividing by odd numbers rarely lands on a perfectly clean fraction. This calculator treats anything within about 1% of a standard ratio as a match — for example, 2560×1080 monitors are commonly sold as “21:9” even though the exact fraction is closer to 64:27 — and shows the plain simplified ratio alongside it so you can see both.
2.39:1 is the anamorphic widescreen ratio used for cinema releases — noticeably wider than the 16:9 you’d see on a TV or monitor. It’s common in film exports and cinematic-style video trailers.
Divide the ratio out once and reuse it. For W:H, height = width × H ÷ W and width = height × W ÷ H — so 16:9 means multiplying a width by 0.5625 (1600 px wide gives 900 px tall), and 4:5 means multiplying by 1.25 (1600 px wide gives 2000 px tall). The solver is doing exactly this, which is why filling in either W2 or H2 is enough; the table above prints the same multiplier applied to 1080 px if you would rather read it off than work it out.
Because the whole-number form stopped being useful. A 1200 × 628 link-preview image reduces exactly to 300:157, which tells you nothing at a glance, so any pair that will not reduce to numbers of 200 or below is shown in decimal form instead — 1.91:1 here. It is the same ratio, only readable, and it also gets no standard-ratio name, because none of the presets sit within about 1% of it.
Crop when the subject has spare room around it: you keep full resolution and lose the edges. Pad when nothing in the frame can go: you keep every pixel and spend screen space on bars. Putting a 1920 × 1080 frame into a 9:16 canvas is the clearest example of the trade — cropping leaves a strip 607.5 px wide out of 1920, while padding leaves roughly 656 px of bar above and below a full-width placement. Use the solver to get those figures first, then decide.
Because the ratio genuinely lands there and rounding it would change the ratio. A 1080 px width at 16:9 is exactly 607.5 px tall. Results are shown as whole pixels wherever rounding moves the value by less than a twentieth of a pixel, and with one decimal otherwise, so the decision to round up or down stays yours — exported files still need whole pixels, and one pixel either way is invisible.