Claude Sonnet 4.5 vs Claude Sonnet 4 vs o3
Too close to call on our weighted score (o3 58, Claude Sonnet 4.5 55, Claude Sonnet 4 51). The right pick depends on what you value most.
AnthropicClaude Sonnet 4.5
55/100- ECI146.8
- Price$3.00 / $15.00
- Context200K
- Anthropic
Claude Sonnet 4
51/100- ECI141.7
- Price$3.00 / $15.00
- Context200K
OpenAIo3
58/100- ECI146.9
- Price$2.00 / $8.00
- Context200K
Too close to call
It is close. Our weighted score puts them within 3 points (o3 58/100, Claude Sonnet 4.5 55/100, Claude Sonnet 4 51/100), so choose by what matters most for your work: o3 for raw capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- Capabilityo3Capabilities Index (ECI): o3 146.9 · Claude Sonnet 4.5 146.8 · Claude Sonnet 4 141.7
- Lowest priceo3o3 $3.50 · Claude Sonnet 4.5 $6.00 · Claude Sonnet 4 $6.00 per 1M tokens (3:1 blend)
- Longest contextAbout the sameClaude Sonnet 4.5 200,000 · Claude Sonnet 4 200,000 · o3 200,000 tokens
- Widest inputsSame inputsClaude Sonnet 4.5: Text, Images, PDFs · Claude Sonnet 4: Text, Images, PDFs · o3: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Sonnet 4.5 | Claude Sonnet 4 | o3 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 74 | 68 | 74 |
| Price | 25% | 13 | 13 | 24 |
| Inputs & features | 15% | 80 | 70 | 80 |
| Context window | 10% | 32 | 32 | 32 |
| Overall | 100% | 55/100 | 51/100 | 58/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Sonnet 4.5Anthropic | Claude Sonnet 4Anthropic | o3OpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 146.8 | 141.7 | 146.9 (best) |
| ECI rank | #64 of 148 | #94 of 148 | #63 of 148 (best) |
| GPQA DiamondGraduate-level science questions | 82.3% (best) | 79.2% | 81.8% |
| FrontierMath Tiers 1–3Research-level mathematics | 23.9% | — | 33.3% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 77.8% | 71.1% | 84.4% (best) |
| SWE-bench VerifiedFixing real GitHub issues | 71.3% (best) | — | 62.3% |
| SimpleQA VerifiedShort factual questions | 30.7% | — | 49.4% (best) |
| Price per million tokens | |||
| Input | $3.00 | $3.00 | $2.00 (best) |
| Output | $15.00 | $15.00 | $8.00 (best) |
| Cached input | $0.30 (best) | — | $0.50 |
| Blended (3:1) | $6.00 | $6.00 | $3.50 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official Anthropic API | Median of 9 providers | Official OpenAI API |
| Limits | |||
| Context window | 200,000 tokens | 200,000 tokens | 200,000 tokens |
| Max output | 64,000 tokens | 64,000 tokens | 100,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yes | Yes | Yeslow · medium · high |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | No | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | claude-sonnet-4-5 | — | o3 |
| API providers | 28 (best) | 9 | 18 |
| Released | Sep 29, 2025 | May 22, 2025 | Apr 16, 2025 |
| Knowledge cutoff | Jul 31, 2025 | Mar 31, 2025 | May 2024 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Sonnet 4.5$60.00
- Claude Sonnet 4$60.00
- o3$36.00
Which should you choose?
Which is better: Claude Sonnet 4.5, Claude Sonnet 4 or o3?
It is close. Our weighted score puts them within 3 points (o3 58/100, Claude Sonnet 4.5 55/100, Claude Sonnet 4 51/100), so choose by what matters most for your work: o3 for raw capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Claude Sonnet 4.5, Claude Sonnet 4 or o3?
o3 is cheaper at $2.00 input / $8.00 output per million tokens (official OpenAI API price). Claude Sonnet 4.5 costs $3.00 input / $15.00 output per million tokens (official Anthropic API price); Claude Sonnet 4 costs $3.00 input / $15.00 output per million tokens (median across 9 API providers). At a typical mix of three input tokens to one output token, that is $3.50 per million tokens for o3 versus $6.00 for Claude Sonnet 4.5 (1.7× as much) and $6.00 for Claude Sonnet 4 (1.7× as much).
Which scores higher on benchmarks?
o3 scores higher on the Capabilities Index (ECI): o3 146.9 (#63 of 148), Claude Sonnet 4.5 146.8 (#64 of 148) and Claude Sonnet 4 141.7 (#94 of 148). The confidence ranges of the top two overlap (144.9–148.6 vs 145.3–148.5), so treat the gap as small. On individual benchmarks: GPQA Diamond — Claude Sonnet 4.5 82.3%, o3 81.8%, Claude Sonnet 4 79.2%; OTIS Mock AIME 2024–2025 — o3 84.4%, Claude Sonnet 4.5 77.8%, Claude Sonnet 4 71.1%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 4 yet, so there is no like-for-like coding score. On overall capability, o3 leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Claude Sonnet 4.5, Claude Sonnet 4 and o3 share the same 200,000-token context window. Maximum output per response: Claude Sonnet 4.5 up to 64,000, Claude Sonnet 4 up to 64,000, o3 up to 100,000 tokens.
Which can read images, PDFs, audio or video?
Claude Sonnet 4.5 accepts text, images and PDFs; Claude Sonnet 4 accepts text, images and PDFs; o3 accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. Claude Sonnet 4.5, Claude Sonnet 4 and o3 are proprietary and only available through APIs and apps.
Which is newer?
Claude Sonnet 4.5 is the newest, released Sep 29, 2025. Claude Sonnet 4 came out May 22, 2025; o3 came out Apr 16, 2025. Knowledge cutoff: Claude Sonnet 4.5 Jul 31, 2025, Claude Sonnet 4 Mar 31, 2025, o3 May 2024.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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