Midjourney --ar Parameter: The Aspect Ratio Reference (2026)

TL;DR: --ar W:H sets a Midjourney image's shape. Default is 1:1, integers only, no decimals. Midjourney's own Version chart caps it at 14:1 on V6, V7, V8.1 and V8.2, dropping to 4:1 when HD is on. The 2:1 ceiling most guides still quote is Version 4 era. Checked August 26, 2026.

What is the --ar parameter in Midjourney?

--ar sets the shape of your image, written as two integers separated by a colon, width first. Midjourney's Aspect Ratio article documents --ar and --aspect as the same parameter and states that the default is 1:1.

The formatting rules Midjourney publishes are short, and three of the four are about punctuation:

• Parameters go at the end of the prompt, after all descriptive text.
• Leave a space before the dashes. poppies--ar 2:3 fails.
• No punctuation inside the parameter. A trailing comma fails.
• No decimals. --ar 1.39:1 is invalid; write --ar 139:100.

a lone lighthouse on a basalt cliff, storm light, long exposure --ar 16:9 --v 8.2

Midjourney reduces the fraction for you. Its docs give the worked example: type --ar 1920:1080 and it simplifies to 16:9. For paper sizes, drop the decimal point rather than rounding. US Letter at 8.5 by 11 inches becomes --ar 85:110, and that is Midjourney's own suggested input, not a workaround.

You can also set a default ratio in the settings panel next to the Imagine bar, which then applies to every prompt you run until you change it. That is the setting most people forget they touched.

What is the maximum aspect ratio in Midjourney?

14:1, on V6, V7, V8.1 and V8.2. If HD is switched on, the ceiling drops to 4:1.

That figure comes from one place: the Feature Compatibility chart in Midjourney's Version article, whose Max. Aspect Ratio row reads 14:1 for V6, 14:1 for V7, and 14:1 (4:1 for HD) for V8.1 and V8.2.

This is the single most misreported number in Midjourney documentation. Search for a max aspect ratio today and you will mostly be told 1:2 to 2:1. That range is real, and Midjourney still publishes it, but the Legacy Features article assigns it to Version 4 and Niji 4. The same legacy table records Version 5 and Version 6 as accepting any ratio.

Two caveats Midjourney attaches to the wide end of that range, both from the Aspect Ratio article: older versions may not support all ratios, and extremely wide or tall ratios are experimental and may produce unpredictable results. Treat anything past roughly 3:1 as a draft medium rather than a delivery format.

Every aspect ratio worth knowing, in one table

There is no whitelist. --ar takes any pair of integers inside the version ceiling, which means the useful reference is not a list of legal values but a list of ratios that map to something you actually ship.

"Not published" is doing honest work in that column. Midjourney publishes exact pixel dimensions for four ratios and no more. Every page you will find with a fifteen-row pixel table has calculated those numbers rather than sourced them, and as the next section shows, calculating them is exactly where it goes wrong.

The four ratios on the web ratio slider called out in Midjourney's January 20, 2026 changelog entry are 6:11, 4:5, 5:4 and 21:9, added alongside whatever the slider already carried. That changelog line is the only inventory of the slider's presets that Midjourney has published.

What size are Midjourney images at each aspect ratio?

At the default 1:1 ratio in V8.2, standard resolution is 1024 by 1024 pixels and HD is 2048 by 2048. Midjourney's Upscalers article publishes a table for three other ratios, and that table is the entire published record.

Two patterns fall straight out of those eight numbers, and both are checkable rather than asserted.

Every single figure is a multiple of 16. So is every figure in Midjourney's separate video dimensions table. Output is snapped to a 16-pixel grid, which is why the ratios do not always come out clean.

The HD column is exactly double the SD column in all four rows. Midjourney adds its own hedge underneath the table, that exact HD dimensions in some aspect ratios may vary slightly, so treat doubling as the pattern rather than the promise.

Why --ar 16:9 does not give you exactly 16:9

Because 1456 divided by 816 is 1.7843, and 16 divided by 9 is 1.7778. Your widescreen image is roughly 0.37 percent wider than widescreen.

You do not have to take my arithmetic for it. Midjourney labels the delivered ratios itself, in the dimensions table in its Video article, where the column for a 16:9 starting image reads 91:51 and the column for a 4:3 starting image reads 77:58. Those are 1456:816 and 1232:928 reduced.

The ratios that survive intact are the ones whose reduced form lands on multiples of 16 without help. 1:1 and 2:3 do. 4:3 and 16:9 do not, so they get nudged to the nearest legal pair.

Nobody will spot half a percent by eye. It matters in exactly two places: when you are compositing a render into a fixed frame, and when a platform will crop anything that is not spec. In both cases, crop deliberately in your editor rather than trusting --ar to hit the number. Midjourney's own footnote on the video table says the same thing in gentler language, that it may need to adjust the ratio slightly in some cases.

What happens if you use an unsupported aspect ratio?

Midjourney does not publish this. There is no documented list of error strings, no stated behaviour for an out-of-range value, and no note about whether a rejected --ar fails the job or silently falls back to 1:1. I looked for it across the whole help centre and it is not there.

What Midjourney does document is the four ways a ratio goes wrong before it ever reaches the model:

1. A decimal. --ar 1.39:1 is rejected outright. Multiply both sides until they are integers.
2. A version mismatch. Older models genuinely cannot render some ratios, and the ceilings differ per version.
3. HD. Anything past 4:1 with HD enabled is outside the documented range even though the same value is fine in SD.
4. Formatting. Missing space, trailing comma, or parameters placed mid-prompt.

If a ratio is not applying and none of those four is the cause, the next thing to check is your saved default in the settings panel, because a default ratio overrides nothing but quietly wins whenever your prompt omits --ar. This is the same class of silent-default problem that makes people think their Midjourney prompts have stopped working when the prompt was never the issue.

Which versions support which aspect ratios?

Two things to flag rather than paper over.

V6 is documented twice, with different answers. The current Version chart says 14:1. The Legacy Features compatibility table says "any". Both pages were live on August 26, 2026. If you are running V6 for character work, test the wide end before you plan around it.

Niji 7 has no separately published ceiling. The Version chart puts --niji 7 in the V7 column, and that column reads 14:1, but Midjourney nowhere states a Niji maximum in its own words. The Niji documentation lives on nijijourney.com, which returns 403 to automated fetches. Treat 14:1 for Niji 7 as an inference from chart placement, not a published figure.

Version-specific parameter support is a running theme across current Midjourney, not just an --ar quirk. The same chart is why --style raw behaves differently on V8.2 than most guides claim, and why --cref and --oref are not interchangeable.

How does aspect ratio interact with upscaling?

Upscaling doubles your pixel dimensions and mostly preserves your ratio. Mostly is the operative word, and Midjourney says so twice.

The Aspect Ratio article warns that some aspect ratios may be slightly changed when upscaling. The Upscalers article warns that exact HD pixel dimensions in some ratios may vary slightly. Neither says which ratios, or by how much.

The mechanics, from the Upscalers and Version articles:

• Subtle and Creative upscalers both double the image. Subtle preserves the original closely; Creative adds detail and changes the image somewhat.
• HD images cannot be upscaled further. They generate at full size and the upscale path stops there.
• Upscaling costs roughly double the GPU time of the original generation, listed as about 2 minutes against 0.8 for an SD prompt set.
• Pan, Zoom Out and Vary Region downscale an HD image to SD. You then have to upscale it back. This is the trap that quietly costs you resolution when you are fixing framing on an HD render.

That last one has a related fix in Midjourney's August 21, 2026 changelog, which records that Vary now respects your settings instead of quietly running in HD, and that HD selection on V8.2 was fixed. If you tested HD behaviour before late August 2026, retest it.

How do you change the aspect ratio of an image you already made?

Three documented routes, all of them extending the canvas rather than cropping it.

The Editor. Open the image in the editor on midjourney.com, then use the Move / Resize panel. It offers preset ratios, a custom ratio field, and draggable grey bars on the canvas edges. This is the only route that lets you type an arbitrary ratio.

Pan. Extends the canvas in one direction and fills the new space with matching detail. Pan runs on V6.1 even when your original was V7 or V8.1, which is worth knowing before you compare the seam. In Discord, panning is only available on V8.1 SD images.

Custom Zoom with the zoom value set to 1. Midjourney documents this as a pro tip in its Zoom Out article: set zoom to 1 so nothing actually zooms, then change the --ar in the prompt text. There is also a Make Square button on any non-square image, which expands whichever dimension is short.

Is HD on by default? Midjourney's own docs disagree

They do, and the disagreement is old enough to have a paper trail. Both readings were live on August 26, 2026.

HD is default. The V8.1 release post of April 14, 2026 states that HD mode is 3x faster and 3x cheaper, and adds: "It's so cheap we're making it default for V8.1."

HD is opt-in. The Version help article describes turning HD on in the settings panel or with the --hd and --sd parameters. The Upscalers article says your V8.2 SD images start at 1024 by 1024. And the changelog entry of April 30, 2026 says the quiet part outright: "To save compute during a server transition, we're making SD default for a bit."

The likeliest reading is that the April 14 announcement was reversed on April 30 and never edited, and that SD has been the practical default since. That is an inference. The check that is not an inference: generate one image, open it, and read its pixel dimensions. 1024 on the short side is SD. This matters for --ar because HD is where your ceiling drops from 14:1 to 4:1.

While we are dating things: the changelog dates the V7-to-V8.1 default switch to June 11, 2026, and the Version help article dates it to June 10. One of them is off by a day. It does not change anything, but it is a fair sample of how tightly these pages are kept in sync.

Render the ratio comparison yourself

The genuinely useful asset here is one prompt that renders the same subject at every ratio you care about, so you can see how framing changes rather than reading about it. Midjourney supports this natively through permutations, and its Permutations article uses an aspect ratio comparison as its own worked example: put your ratios in curly braces, separated by commas, and one line becomes several jobs.

a lone lighthouse on a basalt cliff, storm light, long exposure --ar {1:1, 4:3, 2:3, 16:9} --v 8.2

That is four jobs from one line. Extend it to the shapes you actually deliver in:

editorial portrait of a ceramicist in her studio, north window light, 85mm --ar {1:1, 4:5, 2:3, 9:16} --v 8.2

wide establishing shot of a rain-slick harbour at dusk, cinematic --ar {16:9, 2:1, 21:9} --raw --v 8.2

Run one of these and the real lesson arrives fast: the ratio is not a container you pour a prompt into. The same lighthouse description that reads as a landscape at 16:9 reads as a mistake at 9:16, because a wide establishing shot and a tall frame want different subject placement, different negative space, and different prompt structure entirely.

That is the part --ar cannot fix. A 9:16 prompt that describes a sweeping horizontal vista is fighting itself, and no parameter resolves the argument. This is where writing the prompt to match the frame matters more than the parameter you append to it, and it is the same discipline behind choosing style modifiers deliberately rather than stacking them.

Prompt Architects does not generate images and will not change your --ar ceiling. What it does is turn a rough description into a structured prompt with the framing, subject placement and constraints made explicit, which is what stops a portrait-ratio render from reading like a cropped landscape. If you want the ratio-aware starting points rather than the theory, the Midjourney prompt builder is the faster route.

How to check any of this in 60 seconds

Version-specific parameter documentation is the fastest-rotting content on the internet. V8.0 launched in March 2026 and was retired in July. Everything above carries a date for that reason, and here is how to re-date it yourself.

docs.midjourney.com returns HTTP 403 to direct fetches, which is a bot filter, not a dead site. The pages load fine in a browser. If you want to script it, the docs run on Zendesk, and the Help Center JSON API answers normally:

# List every article, with titles and last-updated timestamps
curl -s "https://docs.midjourney.com/api/v2/help_center/en-us/articles.json?per_page=100"

# Fetch one article; the response includes its own html_url and updated_at
curl -s "https://docs.midjourney.com/api/v2/help_center/en-us/articles/31894244298125.json"

Article 31894244298125 is Aspect Ratio. 32199405667853 is Version, which holds the compatibility chart. 32804058614669 is Upscalers, which holds the pixel table. Check the updated_at field before you trust anything, including this page.

Sources and dates

Every claim above was verified against Midjourney's own documentation on August 26, 2026.

• Aspect Ratio, doc updated July 27, 2026. Syntax, the no-decimals rule, the experimental-extremes warning.
• Version, doc updated July 24, 2026. The compatibility chart, the 14:1 and 4:1 figures, release and retirement dates.
• Upscalers, doc updated July 27, 2026. The four-row pixel table, upscaler behaviour, HD upscale limits.
• Image Size & Resolution, doc updated July 27, 2026. V8.2 HD and SD dimensions at 1:1.
• Legacy Features, doc updated July 9, 2026. Per-version maximum ratios for V3, V4, V5, Niji 4, Niji 5 and the test models.
• Video, doc updated June 11, 2026. The 77:58 and 91:51 delivered-ratio labels.
• Permutations, doc updated July 27, 2026. Brace syntax, plan caps, the Relax-mode exclusion.
• Zoom Out, doc updated July 27, 2026. Custom Zoom at value 1, Make Square.
• Pan, doc updated July 27, 2026. Canvas extension, the V6.1 fallback.
• Editor, doc updated July 27, 2026. Move / Resize presets and the custom ratio field.
• Updates changelog, entries dated January 20, March 17, April 14, April 30, June 11, July 24 and August 21, 2026. Slider presets, the HD default reversal, the Vary fix.

Known unknowns, stated rather than guessed: Midjourney publishes pixel dimensions for four aspect ratios only, publishes no behaviour for out-of-range --ar values, publishes no separate Niji 7 ceiling, and contradicts itself on both the V6 maximum ratio and whether HD is the default. If you need certainty on any of those four, the only reliable instrument is a test render.