You generate a sharp 1:1 image, then remember your blog hero needs to be 1.91:1 and your Story is 9:16. Now you are recropping, or burning a second generation. This is the page I keep open while shipping AI images to more than one surface: a single table of the correct ratio for each destination as of June 2026, the exact pixel dimensions, and the prompting habits that keep the focal point inside the eventual crop. Pick the ratio before you generate and most “regenerate at a different size” runs simply disappear.
TL;DR
- Blog hero / link preview (OG):
1200x630(1.91:1). One image covers Facebook, LinkedIn, Slack, Discord, and X’s large card. - Instagram feed:
1080x1350(4:5) is the in-feed standard; design for the new 3:4 grid crop (see below). Square 1:1 is now legacy. - Stories / Reels / TikTok:
1080x1920(9:16), full-screen vertical. - YouTube thumbnail:
1280x720(16:9). - Pinterest:
1000x1500(2:3); anything taller than 1:2.1 gets truncated. - The big change for 2026: the leading models now generate non-square natively, so you rarely have to crop. GPT Image 2 (in ChatGPT since April 21, 2026) does 3:1 through 1:3; Midjourney’s
--artakes whole-number ratios up to roughly 1:2–2:1.
The reference table
Generate at the ratio in the third column. The pixel dimensions are the modern “good enough” upload size — large enough to stay sharp, not so large you waste generation budget.
| Destination | Ratio | Generate at | Notes (June 2026) |
|---|---|---|---|
| Blog hero / OG / link preview | 1.91:1 | 1200x630 | Universal share image; keep text in the center 1080x600 safe zone. |
| X (Twitter) large card | 2:1 | 1200x600 | A 1200x630 OG image also works; X trims a few pixels top/bottom. |
| Instagram feed (in-feed) | 4:5 | 1080x1350 | Meta’s recommended feed size; taller than 1:1 wins reach. |
| Instagram grid preview | 3:4 | 1080x1440 | The profile grid now previews at 3:4; a 4:5 post is cropped here. |
| Instagram square (legacy) | 1:1 | 1080x1080 | Still accepted, but no longer the default for organic. |
| Stories / Reels / TikTok | 9:16 | 1080x1920 | Keep critical content ~250px from the top and ~350px from the bottom. |
| YouTube thumbnail | 16:9 | 1280x720 | Must read at 320x180, the smallest rendered size. |
| Pinterest pin | 2:3 | 1000x1500 | Pinterest’s recommended ratio; taller than 1:2.1 gets cut in feed. |
| Print A4 landscape | ~1.41:1 | 3508x2480 @300 DPI | A4 is 297x210mm; switch to A3/A2 at the same DPI for posters. |
| iPhone app splash | ~9:19.5 | 1290x2796 | iPhone 15/16 Pro Max logical size; use percentage layouts, not pixel pinning. |
| App Store screenshot | ~9:19.5 | 1290x2796 | Reserve roughly the top 18% for the device signal/status area. |
A useful rule: generate at the target ratio about 20% larger than the final upload, then scale down for crispness. Down-scaling sharpens; up-scaling invents detail and costs more.
How the 2026 models actually set ratios
The single biggest workflow change since this topic mattered: the frontier image models stopped being square-only, so “crop it later” is no longer the default tax.
- GPT Image 2 / ChatGPT Images 2.0 — Shipped in ChatGPT on April 21, 2026. It supports the full range from 3:1 (ultra-wide) to 1:3 (tall), including native 16:9 and 9:16, at 2K standard resolution (4K is in API beta). Earlier GPT Image versions only gave you 1:1, 3:2, and 2:3, which is why so many older workflows assumed a manual crop step. You can simply ask in plain language (“make it 16:9 landscape”) and it respects the request.
- Midjourney — Use the
--arflag, e.g.--ar 16:9or--ar 4:5. Two rules trip people up:--artakes whole numbers only (write139:100, never1.39:1), and the reliable range is about 1:2 to 2:1. Extreme ratios like 3:1 are flagged experimental and can drift. The aspect ratio can shift slightly on upscale, so confirm the final pixels. - Google Gemini (Nano Banana family in the Gemini app) — Set the ratio in the prompt or the app’s size selector; it handles the common 1:1, 16:9, 9:16, 4:5, and 3:2 reliably. As with any model, run one test frame on an unusual ratio before batching.
If your model still only outputs squares, that is the signal to upgrade — every other downstream problem in this guide stems from a square-only generator.
The Instagram 3:4 grid trap
Instagram retired the square grid in 2025; profile grids now preview every post at 3:4 (1080x1440). This creates a quiet failure mode. If you upload the recommended in-feed 4:5 (1080x1350), Instagram crops the top and bottom on the grid view. A post that looks balanced in the feed can have a face or headline clipped on your profile.
Two ways to handle it, as of June 2026:
- Design at 3:4 (
1080x1440). It displays uncropped on the grid and still reads well in feed. This is the safest single ratio if your profile aesthetic matters. - Upload 4:5 (
1080x1350) but keep faces, logos, and text inside the center ~75% vertically, so nothing important lives in the strip the grid trims.
Prompting so the crop survives
Aspect ratio is only half the battle — composition has to anticipate the crop.
- State the ratio explicitly, every time. Some models silently fall back to 1:1 if the request is ambiguous. With Midjourney that means an
--arflag on every prompt; with chat-based generators, name the orientation in words. - Place the focal point where the crop keeps it. For 9:16, push the subject toward the vertical center; the top and bottom belong to system UI and platform chrome.
- Match source ratio in img2img and inpainting. A mismatched reference forces the model to invent a new composition around your image. Keep the canvas ratio identical to the source.
- Change one variable at a time. Don’t alter the subject and the ratio in the same prompt, or you can’t tell which change moved the composition.
Quality check before you ship
- Crop to the target dimensions yourself. If you have to drag the crop frame more than about 10% to save the focal point, the model did not compose for the ratio — regenerate.
- View at the real display size. A 1280x720 thumbnail that looks great full-screen can be illegible at 320x180. Faces and text both need to read small.
- Overlay the mobile safe-area mask for 9:16 destinations. Anything in the top notch/status zone or bottom gesture/caption zone fails on real devices.
- For OG images, validate the preview. Use Facebook’s Sharing Debugger and the X/Twitter card validator before you rely on a link preview in a launch.
Common mistakes
- Generating 1:1 for everything. Square is now the legacy case on almost every surface; your image gets letterboxed or cropped in non-square placements.
- Cropping after the fact. The model didn’t compose for your crop, so focal points get cut. With native 16:9/9:16 support in 2026 models, there is rarely a reason to do this.
- Ignoring the Instagram grid crop. 4:5 in feed looks fine, then loses its top and bottom on the 3:4 grid.
- Using decimals in Midjourney
--ar. Write139:100, not1.39:1, or the parameter is rejected. - Over-generating at max resolution. Slow and expensive for no visible benefit past about 2x the display size; down-scale instead.
- Trusting “auto” aspect ratio. Confirm the actual output dimensions; a model that promises 16:9 in prose can still hand you a square.
FAQ
- Does aspect ratio affect image quality? Slightly. Common ratios (1:1, 4:5, 16:9, 9:16, 2:3) are well covered in training data. Extreme ratios like 3:1 or 1:4 can produce odd compositions, and on Midjourney they are flagged experimental.
- Why does my 16:9 image look stretched? Older or square-trained checkpoints subtly stretch faces and bodies at wide ratios. Newer models (GPT Image 2, Gemini, Midjourney v7) handle wide ratios natively; if you’re on an old Stable Diffusion checkpoint, switch to one trained on varied ratios.
- Can I turn a 1:1 into a 16:9? Only with outpainting, and only if the original composition leaves room on the sides. Otherwise it’s faster and cleaner to generate fresh at 16:9, which every 2026 frontier model supports.
- What ratio covers both OG and X cards?
1200x630(1.91:1). X’s large card prefers 2:1 but accepts the OG image and trims a few pixels top and bottom, so one file works for both. - Is Instagram still 1:1? No. As of 2026 the in-feed standard is 4:5 (
1080x1350) and the profile grid previews at 3:4 (1080x1440). Square is accepted but legacy. - Does Pinterest still favor 2:3? Yes.
1000x1500(2:3) is Pinterest’s recommended size; anything taller than 1:2.1 gets truncated in the feed.