Model comparison
GPT-5.4 Pro vs Mercury 2.5
GPT-5.4 Pro is the stronger model overall, scoring 58.9 to 33.5 on the Noometry Index. Mercury 2.5 costs 1000× less per token, which makes it the better buy when GPT-5.4 Pro's lead doesn't matter for your workload.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. GPT-5.4 Pro scores higher in 3 categories and Mercury 2.5 in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.4 Pro leads 72.4 to 23.3.
- The biggest single-benchmark swing is CritPt: 30% for GPT-5.4 Pro and 0% for Mercury 2.5.
- Mercury 2.5 is cheaper at $0.04 / $0.15 per million input/output tokens, against $30 / $180 for GPT-5.4 Pro.
- GPT-5.4 Pro accepts more context: 1.05M tokens versus 260K.
Side by side
| GPT-5.4 Pro | Mercury 2.5 | |
|---|---|---|
| Provider | OpenAI | Inception |
| Noometry Index | 58.9 | 33.5 |
| Released | 2026-03-05 | 2026-09-08 |
| Weights | Proprietary | Proprietary |
| Context window | 1.05M | 260K |
| Max output | 128K | 66K |
| Input $ / M tokens | $30 | $0.04 |
| Output $ / M tokens | $180 | $0.15 |
| Results tracked | 16 | 4 |
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Category by category
Coding GPT-5.4 Pro leads
GPT-5.4 Pro: 43.2 (#90), Mercury 2.5: 39.5 (#156)
Reasoning GPT-5.4 Pro leads
GPT-5.4 Pro: 70.7 (#13), Mercury 2.5: 22.4 (#193)
| Benchmark | GPT-5.4 Pro | Mercury 2.5 |
|---|---|---|
| CritPt | 30% | 0% |
| ARC-AGI-2 | 83.3% | — |
| SimpleBench | 74.1% | — |
| ARC-AGI-1 | 94.5% | — |
| Chess Puzzles | 58.6% | — |
| EnigmaEval | 23.8% | — |
| Epoch Capabilities Index | 158.93 | — |
Math GPT-5.4 Pro leads
GPT-5.4 Pro: 72.4 (#22), Mercury 2.5: 23.3 (#272)
| Benchmark | GPT-5.4 Pro | Mercury 2.5 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 82.5% | — |
| FrontierMath Tier 4 | 58.5% | — |
| ProofBench | — | 3% |
| FrontierMath (Feb 2025 set) | 50% | — |
| FrontierMath Tier 4 (v1) | 37.5% | — |
Knowledge Not comparable
GPT-5.4 Pro: 68.3 (#7), Mercury 2.5: —
| Benchmark | GPT-5.4 Pro | Mercury 2.5 |
|---|---|---|
| GPQA Diamond | 94.6% | — |
| Humanity's Last Exam | 44.3% | — |
| SimpleQA Verified | 46.3% | — |
| Vectara Hallucination Rate | 8.3% | — |
Frequently asked questions
Is GPT-5.4 Pro better than Mercury 2.5?
GPT-5.4 Pro is the stronger model overall, scoring 58.9 to 33.5 on the Noometry Index. Mercury 2.5 costs 1000× less per token, which makes it the better buy when GPT-5.4 Pro's lead doesn't matter for your workload.
Which is cheaper, GPT-5.4 Pro 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-5.4 Pro lists at $30 and $180.
Is GPT-5.4 Pro or Mercury 2.5 better for coding?
GPT-5.4 Pro scores higher on coding benchmarks: 43.2 versus 39.5 in the Noometry coding category.
Which has the bigger context window?
GPT-5.4 Pro does, with 1.05M tokens against 260K.
How many benchmarks do GPT-5.4 Pro and Mercury 2.5 share?
1 benchmark has published results for both models. GPT-5.4 Pro has 16 scored results on Noometry and Mercury 2.5 has 4.