Model comparison
GPT-5-Codex vs Mercury 2.5
GPT-5-Codex is the stronger model overall, scoring 37.9 to 33.5 on the Noometry Index. Mercury 2.5 costs 51× less per token, which makes it the better buy when GPT-5-Codex's lead doesn't matter for your workload.
Last verified . 0 shared benchmarks.
Summary
- The widest gap is in reasoning, where GPT-5-Codex leads 30.9 to 22.4.
- Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $1.25 / $10 for GPT-5-Codex.
- GPT-5-Codex accepts more context: 400K tokens versus 260K.
Side by side
| GPT-5-Codex | Mercury 2.5 | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 37.9 | 33.5 |
| Released | 2025-09-15 | 2026-09-08 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 260K |
| Max output | 128K | 66K |
| Input $ / M tokens | $1.25 | $0.04 |
| Output $ / M tokens | $10 | $0.15 |
| Results tracked | 3 | 4 |
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Category by category
Coding GPT-5-Codex leads
GPT-5-Codex: 42.4 (#103), Mercury 2.5: 39.5 (#156)
Agentic & Tool Use Not comparable
GPT-5-Codex: 31.0 (#72), Mercury 2.5: —
| Benchmark | GPT-5-Codex | Mercury 2.5 |
|---|---|---|
| Terminal-Bench | 44.3% | — |
Reasoning GPT-5-Codex leads
GPT-5-Codex: 30.9 (#83), Mercury 2.5: 22.4 (#193)
| Benchmark | GPT-5-Codex | Mercury 2.5 |
|---|---|---|
| Kagi LLM Benchmark | 70.3% | — |
| CritPt | — | 0% |
Math Not comparable
GPT-5-Codex: —, Mercury 2.5: 23.3 (#272)
| Benchmark | GPT-5-Codex | Mercury 2.5 |
|---|---|---|
| ProofBench | — | 3% |
Frequently asked questions
Is GPT-5-Codex better than Mercury 2.5?
GPT-5-Codex is the stronger model overall, scoring 37.9 to 33.5 on the Noometry Index. Mercury 2.5 costs 51× less per token, which makes it the better buy when GPT-5-Codex's lead doesn't matter for your workload.
Which is cheaper, GPT-5-Codex or Mercury 2.5?
Mercury 2.5 is cheaper. It lists at $0.04 per million input tokens and $0.15 per million output tokens; GPT-5-Codex lists at $1.25 and $10.
Is GPT-5-Codex or Mercury 2.5 better for coding?
GPT-5-Codex scores higher on coding benchmarks: 42.4 versus 39.5 in the Noometry coding category.
Which has the bigger context window?
GPT-5-Codex does, with 400K tokens against 260K.
How many benchmarks do GPT-5-Codex and Mercury 2.5 share?
0 benchmarks have published results for both models. GPT-5-Codex has 3 scored results on Noometry and Mercury 2.5 has 4.