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LLM Toolkit

Model comparison

o3 vs Claude Sonnet 5

Verified pricing, context windows and real-workload costs for both models — computed from official provider rates as of 2026-08-26.

Cheaper input

o3

$2.00 /1M in

Cheaper output

o3

$8.00 /1M out

Bigger context

Claude Sonnet 5

1M tokens

Head to head

Spec o3 Claude Sonnet 5
Input / 1M tokens $2.00 $2.00
Cached input / 1M $0.50 $0.20
Output / 1M tokens $8.00 $10.00
Context window 200K 1M
Provider OpenAI Anthropic
Price verified 2026-08-26 2026-09-02

Monthly cost at three real workloads

Workload o3 Claude Sonnet 5 Winner
Side-project chatbot 30K req · 2,000 in / 500 out · 40% cached $204.00/mo $226.80/mo o3
Coding agent 500K req · 12,000 in / 1,500 out · 70% cached $11,700/mo $11,940/mo o3
Bulk extraction 2,000K req · 800 in / 120 out · 20% cached $4,640/mo $5,024/mo o3

Computed from list prices verified 2026-08-26. Cache savings blend normal and cached input rates by the hit rate; models without published cached rates use the base input price. Adjust every parameter yourself on the API Cost Calculator.

Pick o3 if…

  • You prefer its $2.00 input rate for read-heavy workloads.
  • Your documents fit its 200K window comfortably.
  • You value its provider ecosystem and tooling.

Pick Claude Sonnet 5 if…

  • Output-heavy agent loops favor its $10.00 output rate.
  • You need 1M tokens of context for large codebases or document sets.
  • You want cheaper total spend at your exact volumes — verify with the calculator above.

Frequently asked questions

Is o3 cheaper than Claude Sonnet 5?

o3 is cheaper on input at $2.00 per 1M tokens vs $2.00 — input pricing is about the same. On output, o3 wins at $8.00 vs $10.00. At a balanced workload (100K requests, 2K in / 500 out), o3 runs $800.00/mo vs $900.00/mo — a 1.1× difference.

o3 vs Claude Sonnet 5: which has the bigger context window?

Claude Sonnet 5, with 1M tokens vs 200K — 5.0× more room. Filling Claude Sonnet 5's window once costs $2.00 at list price, vs $0.400 for the smaller window.

Should I switch from o3 to Claude Sonnet 5?

Switch if your bottleneck matches Claude Sonnet 5's strengths: the larger 1M context and its pricing profile. Stay on o3 if your workload already fits its limits. Test both with your real token counts before committing.

Keep comparing

Or measure your real usage with the AI Token Counter and browse all rates on the Pricing Comparison.