AI Cost for Legal 2026:
Contract Review, Research & Document Drafting
Real AI API cost breakdowns for legal teams and legal tech products. Contract review, legal research, NDA drafting, and due diligence automation — with per-document costs and ROI vs. $300–$600/hr lawyer rates. Last verified: 2026-10-01.
Legal AI Use Cases & Per-Task Costs
| Task | Tokens (in/out) | Claude Haiku 4.5 | Claude Sonnet 5.5 | Claude Opus 5.5 |
|---|---|---|---|---|
| NDA review (5 pages) | 4,000 in / 500 out | $0.006500 | $0.013000 | $0.026000 |
| Service agreement review (15 pages) | 12,000 in / 800 out | $0.016000 | $0.032000 | $0.064000 |
| Complex contract review (50 pages) | 40,000 in / 2,000 out | $0.050000 | $0.100000 | $0.200000 |
| Due diligence (100-page M&A doc) | 80,000 in / 3,000 out | $0.095000 | $0.190000 | $0.380000 |
| Legal research query (case law) | 2,000 in / 1,000 out | $0.007000 | $0.014000 | $0.028000 |
| NDA drafting from template | 1,500 in / 2,000 out | $0.011500 | $0.023000 | $0.046000 |
| Employment agreement draft (10 pages) | 2,000 in / 5,000 out | $0.027000 | $0.054000 | $0.108000 |
| Contract clause extraction (50 clauses) | 15,000 in / 2,000 out | $0.025000 | $0.050000 | $0.100000 |
Legal review is input-heavy (large documents) and output-moderate (structured analysis). Use Sonnet for client-facing output; Haiku is adequate for internal screening passes.
AI vs Lawyer Cost: ROI Analysis
| Task | Lawyer time | Lawyer cost (@$400/hr) | AI cost (Sonnet 5.5) | Savings |
|---|---|---|---|---|
| NDA review | 30 min | $200 | $0.013 | 15,000× |
| Service agreement review | 2 hours | $800 | $0.032 | 25,000× |
| Complex contract review | 8 hours | $3,200 | $0.10 | 32,000× |
| Due diligence (100 pages) | 16 hours | $6,400 | $0.19 | 34,000× |
| Legal research query | 1 hour | $400 | $0.014 | 29,000× |
Important caveat: AI provides first-pass analysis, not legal advice. Lawyer review is still required for consequential decisions — AI reduces hours needed, not lawyer involvement entirely.
Which Model for Legal Work
| Task | Recommended model | Why |
|---|---|---|
| Contract screening / triage | Claude Haiku 4.5 | Identify contracts needing lawyer attention; structured output at low cost |
| Clause extraction / classification | Claude Haiku 4.5 | Structured extraction task — Haiku excels at following format templates |
| Client-facing contract summary | Claude Sonnet 5.5 | Quality matters when output goes to clients; better nuance on complex provisions |
| Complex legal analysis (M&A, litigation) | Claude Sonnet 5.5 or Opus 5.5 | High-stakes decisions warrant the best model; cost is still 99% less than billable hours |
| Legal document drafting | Claude Sonnet 5.5 | Better consistency, legal style adherence, and precise clause language vs Haiku |
| Multi-document due diligence | Gemini 2.5 Pro or Claude Opus 5.5 | 100K+ token documents may benefit from Gemini's 1M context at $1.25/M input |
Legal AI Stack: Monthly Cost for a Law Firm
| Firm type | Monthly AI activity | AI cost (Haiku) | AI cost (Sonnet 5.5) | Billable savings |
|---|---|---|---|---|
| Solo / boutique (1–3 lawyers) | 50 NDAs, 20 service agreements, 10 research queries | $1.90 | $3.80 | $12,000+ |
| Mid-size firm (10–20 lawyers) | 500 contracts, 100 research queries, 50 drafts | $15 | $30 | $120,000+ |
| Large firm / legal tech product | 5,000 contracts/mo processed | $125 | $250 | $1M+ |
Even Sonnet 5.5 at $250/month is trivial compared to billable hours saved. The binding constraint is quality and liability, not API cost.
Important: AI Is Not Legal Advice
AI contract review should always be treated as a first-pass tool, not a replacement for legal counsel. Best practice in legal AI deployments:
- Screening pass: AI flags issues and scores risk — attorney reviews flagged sections only (not the whole document)
- Extraction pass: AI pulls key dates, parties, obligations into structured format for attorney review
- Draft generation: AI generates first draft from template; attorney edits and approves
- Privilege and confidentiality: Ensure your AI API agreement covers confidentiality. Anthropic's API does not train on API data by default.
- Hallucination risk: Legal citations from AI must be verified — AI can fabricate case names. Use AI for analysis, not citation.
Calculate Your Legal AI Cost
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