AI トークンに対する画像解像度
詳細ガイド 近日公開
画像解像度から AI トークンへのコンバーターの包括的な教育ガイドを準備中です。ステップバイステップの解説、数式、実例、専門家のヒントをお届けしますので、もうしばらくお待ちください。
The Image Resolution to AI Tokens Converter estimates how many tokens a given image will consume when passed to vision-capable AI models (OpenAI GPT-4o and GPT-4 Vision, Anthropic Claude 3 Opus/Sonnet/Haiku and Claude 3.5/4.x, Google Gemini 1.5 Pro/Flash). Each model uses a different tile-based algorithm to convert pixel dimensions into token cost. Token consumption directly maps to API cost — knowing token counts before sending lets developers budget spend, decide whether to resize, and choose between low-detail and high-detail modes. OpenAI GPT-4o high-detail uses 85 base tokens + 170 tokens per 512×512 tile. A 1024×1024 image needs ⌈1024/512⌉ × ⌈1024/512⌉ = 4 tiles = 85 + 4×170 = 765 tokens (~$0.004 per image at GPT-4o input rates). Low-detail mode is a flat 85 tokens regardless of size — ~9× cheaper for thumbnails, OCR of large text, or classification tasks that don't need fine detail. Claude 3 family uses a simpler formula: tokens ≈ width × height / 750 (so 1024×1024 ≈ 1,400 tokens). Gemini 1.5 charges roughly 258 tokens for any image up to 384×384 plus tiles beyond that. Understanding when to downscale: most vision tasks (object classification, scene description, OCR of standard text) don't benefit from resolutions above 1024 pixels on the long edge. Downscaling a 4K screenshot from 3840×2160 to 1024×576 cuts tokens by ~10× with minimal quality loss for these tasks. Fine detail tasks (handwriting OCR, medical imaging, satellite analysis) benefit from full resolution. For thumbnails or low-stakes classification, OpenAI's low-detail mode is dramatically cheaper. This calculator helps developers budget vision API spend before building image-heavy features (content moderation, e-commerce product analysis, accessibility alt-text generation, document parsing). At GPT-4o pricing (~$5/M input tokens as of mid-2024), 1 million high-detail 1024×1024 images cost ~$3,800. Choosing low-detail mode for the 80% of images that don't need fine detail drops the same workload to ~$425 — a 9× cost reduction.
GPT-4o high: Tokens = 85 + 170 × ⌈W/512⌉ × ⌈H/512⌉; GPT-4o low: 85 flat; Claude 3: ≈ W × H / 750
- 1Step 1 — Enter image width and height in pixels
- 2Step 2 — Select the target AI model (each uses a different tile algorithm and pricing)
- 3Step 3 — Select detail level (OpenAI only — low is 85 tokens flat, high is tile-based)
- 4Step 4 — Calculator applies the model's specific token formula (tiles × per-tile cost + base)
- 5Step 5 — Output displays estimated tokens, tile count (where applicable), and cost per image
- 6Step 6 — Cost projections at 1K and 10K image volumes for budget planning
- 7Step 7 — Compare costs across models to choose the most economical fit for your use case
85 base + 4×170 tile tokens = 765. At $5/M tokens input, ~$0.004 per image.
10× cheaper for thumbnails or classification tasks
Low-detail mode ignores resolution and charges 85 tokens.
Claude formula: width × height / 750 = ~5,600. Higher than OpenAI for same image at high-detail.
Most vision tasks don't need 4K — downscaling first is the single biggest cost lever.
API cost budgeting before launching image-heavy features
Image preprocessing pipeline decisions (resize before upload?)
Detail-mode selection per workload type
Model comparison for vision-based products
Monthly burn rate forecasting for AI startups
Should I always downscale images before sending?
Yes for most use cases — 1024px long edge is sufficient for object recognition, scene description, and standard OCR. For handwriting, medical imaging, satellite analysis, or fine-detail tasks, keep full resolution. Resize using image libraries (Pillow, sharp, ImageMagick) before encoding to base64 or uploading.
When should I use OpenAI low-detail mode?
Use low-detail (85 tokens flat) for: thumbnail classification, content moderation triage, OCR of large text, simple yes/no detection. The 9× cost saving usually outweighs quality loss for high-volume workloads. Reserve high-detail for cases where you've verified quality matters.
Why do Claude and OpenAI charge so differently?
Different tokenization strategies. OpenAI tiles at 512×512 with per-tile token cost (modular). Claude approximates total token count from total pixel count (uniform). Neither is wrong — choose based on cost per use case after benchmarking with real images.
Does base64 encoding affect token count?
Token count is determined by image dimensions, not file size or encoding. A 1MB JPEG and 5MB PNG at the same dimensions consume the same tokens. Base64 inflation only affects upload bandwidth, not API cost.
How accurate are these estimates?
Within ±10% of actual billed tokens. OpenAI publishes the exact formula; Claude and Gemini formulas are approximations from documentation and empirical testing. Always check actual usage in the response object after sending a few test images.
プロのヒント
For thumbnail or classification tasks, use OpenAI low-detail mode — 85 tokens flat regardless of size, ~9× cheaper than high-detail. Reserve high-detail for cases where you've A/B-tested and confirmed quality loss is unacceptable. The biggest cost wins come from picking the right detail level, not from choosing models.
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