What is the cheapest AI API for legal document review?

The cheapest AI API for legal document review is Gemini 2.0 Flash Lite at $0.075/$0.30 per 1M tokens. For contracts and legal documents that require high accuracy, Gemini 2.5 Pro ($1.25/$10.00) or Claude Sonnet 4 ($3.00/$15.00) offer better quality at moderate cost. A typical 50-page contract (~10,000 tokens) costs $0.00075 to review with Flash Lite.

How much does it cost to review contracts with AI?

Reviewing 100 contracts/day (10,000 input / 2,000 output tokens each) costs: Gemini Flash Lite ~$6/month, DeepSeek V4 Flash ~$10/month, GPT-4o mini ~$16/month, Claude Haiku ~$36/month. Premium models like Claude Sonnet 4 cost ~$150/month but provide higher accuracy for complex legal language. Use the calculator above to estimate your specific costs.

Can AI replace lawyers for contract review?

AI can significantly accelerate contract review by flagging risks, extracting key terms, and summarizing clauses — but it doesn't replace legal judgment. The most cost-effective approach is AI-assisted review: use budget models (Gemini Flash, DeepSeek) for initial triage and extraction, then route complex or high-risk contracts to premium models (Claude Sonnet, GPT-5) for detailed analysis. This two-tier approach can reduce review costs by 70-85%.

Cheapest AI API for Legal

Find the cheapest AI API for contract review, legal research, and compliance. We ranked 42 models by cost for legal workloads.

Calculate Your Legal AI Cost

Enter your legal workload to see the cheapest models for your use case.

Legal task:

Documents per day

Avg input tokens per document

Avg output tokens per document

Days per month

Legal API Cost Ranking

Every model ranked by cost for a typical legal workload: 100 documents/day, 10,000 input / 2,000 output tokens per document.

Top Picks by Firm Size

Solo Practitioner / Small Firm (under $50/month)

Gemini 2.0 Flash Lite$6.34/mo

DeepSeek V4 Flash$10.03/mo

GPT-oss 20B$10.21/mo

Mid-Size Firm ($50-200/month)

GPT-4o mini$16.28/mo

Mistral Small 4$16.28/mo

Claude Haiku 4.5$36.00/mo

Enterprise / BigLaw ($200-1000/month)

Claude Sonnet 4$150.00/mo

GPT-5$495.00/mo

Gemini 2.5 Pro$67.50/mo

Strategy: Two-Tier Legal Review Pipeline

Legal work benefits enormously from a two-tier review pipeline — use budget models for initial triage and extraction, then route high-risk documents to premium models.

Two-Tier Legal Pipeline (100 contracts/day)

Tier 1: 80% routine → Gemini Flash ($0.10/$0.40)$21.12/mo

Tier 2: 20% complex → Claude Sonnet 4 ($3/$15)$145.20/mo

Total with pipeline$166.32/mo (vs $495 on GPT-5 for all)

This two-tier approach saves 66% compared to using GPT-5 for everything, while maintaining high accuracy on complex contracts. The key is using AI to classify document complexity first, then routing accordingly.

Legal-Specific Considerations

Accuracy matters more than speed: Legal documents require high precision. A missed clause or incorrect extraction can have serious consequences. Consider premium models for critical contracts.
Context window is critical: Legal documents are often 50-100+ pages. Models with large context windows (Gemini Flash at 1M, Claude at 200K) handle full contracts without chunking.
Input-heavy workload: Legal review is 80-95% input tokens (reading documents) with relatively short outputs (findings, summaries). Input price dominates your cost.
Batch processing: Most legal review is batch (review N documents), not real-time. This means you can optimize by processing during off-peak hours and using async APIs.
Compliance requirements: Ensure your AI provider meets your jurisdiction's data handling requirements. Some legal work requires on-premise or private cloud deployment.

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