# AI Poster Generator: Build the Prompt, Pick the Size URL: https://prexi.art/tools/ai-poster-generator Type: tool Locale: en Published: 2026-08-25 Updated: 2026-08-26 --- > Describe the poster, pick a mood and where it's going. This AI poster generator drops a ready-to-paste prompt with the right aspect ratio already built in. ## The AI Poster Generator That Builds Your Prompt Describe the poster, pick a mood, get a print-ready prompt tuned to Midjourney, Flux, Nano Banana Pro or SD3.5, with the right aspect ratio already worked out. ## Poster Prompt Builder Describe the poster, pick a mood and where it's going. The prompt and the aspect ratio update as you type, nothing is sent anywhere. *[Interactive widget — see the live page for the full experience]* ## What this tool actually does No server-side rendering here, just a prompt built right and the print math done for you. ### Model-aware prompt syntax Midjourney reads aspect ratio straight out of the prompt text, so it gets an inline --ar flag. Flux, Nano Banana Pro and SD3.5 take aspect ratio as a separate setting, so the tool tells you to set it there instead of stuffing it into text that model will ignore. ### Real print math, not a guess Pick Instagram, a flyer, an A2 print or a movie one-sheet, and the tool converts the real ISO 216 paper size, US Letter, or the classic 27x40in one-sheet, into the nearest aspect ratio your generator supports and the minimum pixel count at 300 DPI, the standard commercial print resolution. ### 8 moods we actually reach for Brutalist, riso print, minimal Swiss, vintage Kodachrome, grunge collage, neon cyberpunk, art deco, Y2K. Each one is a tested keyword set pulled from prompts the team runs when moodboarding client posters, not a random adjective dump. ## From blank page to prompt 1. **Describe it** — Type what the poster is for: a show, a product drop, a personal project. One honest sentence is enough, the tool doesn't need a full creative brief. 2. **Pick mood and model** — Choose one of eight tested style keyword sets, then the model you're actually pasting into. Each model changes how the aspect ratio gets written. 3. **Copy and go** — The prompt and the exact aspect ratio update live as you type. Hit copy, paste it into your generator, and adjust from there. ## The numbers behind it - **8** — tested style moods - **4** — models supported - **300** — DPI used for the print math - **0** — signups required ## Before you paste this prompt somewhere ### Does this actually generate the poster image? No. This builds the prompt and the technical specs, aspect ratio and DPI. Paste the result into Midjourney, Flux, Nano Banana Pro or SD3.5 to get the actual image. There's no server-side image generation running behind this page. ### Is it free? Yes. No signup, no email gate. Everything runs in your browser. ### Where do the aspect ratio numbers come from? Real paper and screen standards: ISO 216 for A2 and A3, US Letter, the classic 27x40in movie one-sheet, and common social export sizes, matched to the closest ratio your generator actually accepts. ### Why does Midjourney get an inline flag but Flux doesn't? Because that's how each tool works right now. Midjourney reads aspect ratio straight from the prompt text. Flux, Nano Banana Pro and SD3.5 take it as a separate setting outside the prompt, so stuffing it into the text does nothing. ### Can I use this for a real print run? Use it to get in the right ballpark, aspect ratio and target pixel count at 300 DPI. For anything going to an actual printer, confirm bleed and color profile with them first, this tool doesn't replace a print shop's own specs. ### Why only 8 style moods? Because 8 curated, tested keyword sets beat 40 vague ones. These are the moods we actually reach for when moodboarding client posters, not a dropdown padded out for the sake of it. ### Does it store what I type? No. Nothing leaves your browser except an anonymous ping that the tool got used, no IP, no text, no design brief stored anywhere. ### What if I don't use Midjourney, Flux, Nano Banana or SD3.5? The keyword sets are plain English, they'll work as a starting prompt in Leonardo, Ideogram, or pretty much any text-to-image model. You'll just set the aspect ratio yourself in the tool's own settings, the same way Flux users already do. ## Steal this prompt, then go build the next one. prexi.art tracks what actually works across Midjourney, Flux, Nano Banana and SD3.5, tested, not guessed. *Call to action: Explore more prompts on prexi.art* ## FAQ ### Does this actually generate the poster image? No. This builds the prompt and the technical specs, aspect ratio and DPI. Paste the result into Midjourney, Flux, Nano Banana Pro or SD3.5 to get the actual image. There's no server-side image generation running behind this page. ### Is it free? Yes. No signup, no email gate. Everything runs in your browser. ### Where do the aspect ratio numbers come from? Real paper and screen standards: ISO 216 for A2 and A3, US Letter, the classic 27x40in movie one-sheet, and common social export sizes, matched to the closest ratio your generator actually accepts. ### Why does Midjourney get an inline flag but Flux doesn't? Because that's how each tool works right now. Midjourney reads aspect ratio straight from the prompt text. Flux, Nano Banana Pro and SD3.5 take it as a separate setting outside the prompt, so stuffing it into the text does nothing. ### Can I use this for a real print run? Use it to get in the right ballpark, aspect ratio and target pixel count at 300 DPI. For anything going to an actual printer, confirm bleed and color profile with them first, this tool doesn't replace a print shop's own specs. ### Why only 8 style moods? Because 8 curated, tested keyword sets beat 40 vague ones. These are the moods we actually reach for when moodboarding client posters, not a dropdown padded out for the sake of it. ### Does it store what I type? No. Nothing leaves your browser except an anonymous ping that the tool got used, no IP, no text, no design brief stored anywhere. ### What if I don't use Midjourney, Flux, Nano Banana or SD3.5? The keyword sets are plain English, they'll work as a starting prompt in Leonardo, Ideogram, or pretty much any text-to-image model. You'll just set the aspect ratio yourself in the tool's own settings, the same way Flux users already do.