Stability AI is the company behind Stable Diffusion. Its API generates images from text (and does image-to-image, upscaling and inpainting) and bills in credits rather than tokens. Here's what a generation actually costs, the free credits, and how to start.
| Model / endpoint | Credits per image | ≈ Cost (at ~$0.01/credit) |
|---|---|---|
| Stable Image Core | ~3 credits | ~$0.03 |
| Stable Diffusion 3.5 Large | ~6.5 credits | ~$0.065 |
| Stable Image Ultra | ~8 credits | ~$0.08 |
| Upscale / edit endpoints | ~3–25 credits | ~$0.03–$0.25 |
New accounts get a small one-time pool of free credits to test generation — enough for a few dozen images. It's a trial, not a recurring monthly free quota. If you need ongoing free image generation, running the open Stable Diffusion weights yourself (on a rented GPU or a service like Replicate) can be cheaper at volume, at the cost of setup and ops.
1. Sign up at platform.stability.ai.
2. Open account settings and check your free credits.
3. Go to API Keys and generate a key (starts with sk-).
4. Call a v2beta image endpoint with a Bearer token.
Generate one image:
For text-to-image you have real choice. OpenAI (gpt-image / DALL·E) and Google Gemini both generate images and may be simpler if you already use them for text. Replicate hosts Stable Diffusion and hundreds of other image models on a pay-per-second basis, which is often cheaper for bulk jobs. Stability's edge is being the source of the Stable Diffusion family with editing, upscaling and structure-control endpoints. Estimate your monthly spend with the AI app cost estimator before committing.
You get a small one-time allowance of free credits to test. After that, images are billed in credits (roughly a few cents each). There's no perpetual free monthly quota.
Sign up at platform.stability.ai, open account settings, go to API Keys, and generate a key (it starts with sk-). Use it as a Bearer token on the v2beta image endpoints.
Roughly $0.03 for Stable Image Core, ~$0.065 for SD 3.5 Large and ~$0.08 for Ultra, assuming credits cost about $0.01 each. Edit and upscale endpoints range from a few credits to ~25.
Often comparable. Stable Image Core is among the cheapest hosted options per image; OpenAI and Gemini are competitive and may win on convenience. For high volume, self-hosting the open weights or using Replicate per-second can undercut all of them.
Not affiliated with Stability AI. Prices are reference estimates — always verify on the official pricing page.