Free token cost calculator and prompt diff checker
Diff & Cost Estimate compares your original prompt with a new version side by side. See a word-level diff, the token reduction, and the dollar savings across OpenAI, Anthropic, Google and DeepSeek models.
Why Visual Diffing and Token Cost Estimation are Critical
In modern AI product development, prompt engineering is an iterative software discipline. When tweaking system instructions or compressing few-shot examples, engineers and prompt designers need to know two things immediately: what exact words changed, and how much money was saved.
Diff & Cost Estimate provides side-by-side visual diffing (green additions, red removals) alongside cost projections for each model in the price table below. Whether you are optimizing a prompt for personal ChatGPT use or scaling an enterprise AI agent to millions of monthly API calls, this tool shows what a prompt change is worth in tokens and dollars.
3 Core Metrics Evaluated in the Diff Report
Token Compression Delta
Counts tokens before and after with the GPT-4o tokenizer (exact for GPT-4o, a close reference for other models) and shows the net saving and percentage reduction.
Multi-Model Cost Projections
Calculates dollar savings for every model in the price table below, at your own request volume.
Input and Output Priced Separately
Output length is set per request and held equal for both versions, so the saving shown is the input-token saving.
Estimated Monthly Savings by Model Tier (100k API Calls)
Input-token savings only, based on published pricing as of September 2026 — use the live calculator above for your own prompt, output length, and volume.
| Frontier LLM Model | Original Cost (1,500 Tok) | Optimized Cost (750 Tok) | Monthly Net Savings |
|---|---|---|---|
| OpenAI GPT-4o | $375.00 | $187.50 | +$187.50 / mo |
| Anthropic Claude Sonnet 5.5 | $300.00 | $150.00 | +$150.00 / mo |
| Google Gemini 3.6 Flash | $112.50 | $56.25 | +$56.25 / mo |
| OpenAI GPT-4o mini | $22.50 | $11.25 | +$11.25 / mo |
Model Prices Used by the Calculator
List prices per million tokens as of September 2026 (DeepSeek at off-peak rates). Check each provider’s pricing page before budgeting.
| Model | Input / 1M tokens | Output / 1M tokens | Context window |
|---|---|---|---|
| OpenAI GPT-4o | $2.50 | $10.00 | 128K |
| OpenAI GPT-4o mini | $0.15 | $0.60 | 128K |
| Anthropic Claude Opus 5.5 | $4.00 | $20.00 | 1M |
| Anthropic Claude Sonnet 5.5 | $2.00 | $10.00 | 1M |
| Anthropic Claude Haiku 4.5 | $1.00 | $5.00 | 200K |
| Google Gemini 3.6 Flash | $0.75 | $3.75 | 1.05M |
| Google Gemini 3.1 Pro | $2.00 | $12.00 | 1.05M |
| DeepSeek DeepSeek V4-Flash | $0.15 | $0.60 | 1M |