Grok 4.5
xAI · proprietary · writing benchmark
The short version
Grok 4.5 sits at #30 of 130 on ToneBench, in the middle of the pack, with a writing Elo of 2042 and an overall score of 85.8 out of 100. We measured it by having it write all 9 of our real YouTube scripts, five times each, then scoring every draft blind against our own finished versions. Here is how it shook out.
Inside xAI, this is the strongest writer we tested. It edges out the other 6 xAI configs on the board, so if you're staying in this family for voice work, this is the one to reach for.
Among proprietary models, it comes in 28th of 83. That ranking is against the stronger half of the board: closed models still set the pace on voice fidelity here.
What it does best is Hook: it ranks 19th on that dimension at 88.0, well above the board average. Its softer spot is Length Discipline (78.7, 45th), which is the thing to watch if that metric matters most for your use.
It was uneven across the 9 scripts. Its best run was the product release announcement / personal observation (89.2) and its weakest was the personal technical walkthrough / agentic workflow case study (82.1), a spread of about 7 points. Worth knowing if your writing skews toward one of those formats.
On cost, it runs about $0.038/task. For that money it beats 23 models that cost noticeably more.
Skill profile
The shape is the story: the further a corner reaches, the stronger that dimension. Biggest edge over the board: Visual Cues (+12.0); smallest edge: Anti-Slop (+7.4).
Per-metric scores
Nine writing dimensions, each scored 0–100 and blended by the editorial weight shown. Rank is against all 130 current-ranked models. The thick bar is this model; the thin lines above and below are the current field's best model (darker) and average (lighter) on the same scale. The small ± number is its run-to-run variation.
Per-article scores
The same 9 real scripts every current-ranked model writes, scored individually. Different formats stress different skills.
Consistency: run-to-run variability
Every cell on this page is the mean of 5 independent runs per script; the ± numbers are the run-to-run standard deviation. Overall, Grok 4.5 varies by ± 2.8 points between runs versus a board median of ± 3.8, so it is noticeably steadier than the typical model here.
Its steadiest is YouTube Structure (± 2.0 vs ± 3.6 board median), which you can rely on run after run.
| Metric | This model | Board median | Verdict |
|---|---|---|---|
| Tone & Voice ? | 87.1 ± 1.4 | ± 2.2 | typical |
| Writing Craft ? | 86.6 ± 1.4 | ± 2.0 | typical |
| Substance & Value ? | 87.4 ± 1.8 | ± 2.6 | typical |
| Flow & Emotion ? | 83.5 ± 2.1 | ± 2.6 | typical |
| YouTube Structure ? | 84.4 ± 2.0 | ± 3.6 | steadier than most |
| Hook ? | 88.0 ± 2.1 | ± 3.0 | typical |
| Length Discipline ? | 78.7 ± 6.5 | ± 8.6 | typical |
| Anti-Slop ? | 90.2 ± 2.2 | ± 2.6 | typical |
| Visual Cues ? | 86.5 ± 2.3 | ± 4.7 | steadier than most |
Measured, not modeled
Numbers we log on every run and rarely talk about. None of these affect the writing scores; cost and latency are informational.
What each judge scored it
The published overall of 85.8 is the consensus of three family-disjoint judges scoring the same 45 stored drafts blind with the identical rubric. The highest and lowest judge differ by 7.3 points on its overall. A typical amount of judge disagreement for this board. How the panel works: methodology.
How we ran Grok 4.5
- Accessed viaxAI API · model page ↗
- Exact model / route id
grok-4.5(provider default reasoning) - Generations5 independent runs × 9 scripts = 45 drafts, stored immutably after generation
- Run dates2026-07-29 → 2026-08-11
- Judges3-judge panel: Claude Opus 5, high effort (Anthropic) + DeepSeek V4 Flash (OpenRouter) + GPT-5.6 Sol, medium reasoning (Codex CLI): every draft scored independently by all three with the identical rubric, blind to model identity, evidence quotes required before each metric score; published score = per-metric consensus mean, verified with a Bradley-Terry refit (methodology)
- Samplingprovider-default sampling, no fine-tuning, no system-prompt changes; every current-ranked model gets the identical brief, style contract and research packet
- What stays privatethe exact rubric and any non-public reference material; source-publication timing is disclosed for exceptions (why)
Frequently asked questions
How good is Grok 4.5 at writing?
On ToneBench it ranks #30 of 130 with a writing Elo of 2042 and an overall score of 85.8/100. That score comes from writing our 9 real YouTube scripts five times each and scoring every draft blind against our own finished versions across nine writing dimensions.
Is Grok 4.5 the best xAI model for writing?
Yes. Among the xAI configs we tested, Grok 4.5 is the strongest writer on the board.
Is Grok 4.5 good value for the money?
It costs about $0.038/task. Nothing meaningfully cheaper outscores it, which puts it on the value side of the board.
What are Grok 4.5's strengths and weaknesses?
Its strongest dimension is Hook (19th on the board, 88.0). Its weakest is Length Discipline (45th on the board, 78.7). The full nine-metric breakdown is on this page.
Does Grok 4.5 write some formats better than others?
Yes. Its best of our 9 scripts was the product release announcement / personal observation (89.2) and its weakest was the personal technical walkthrough / agentic workflow case study (82.1).
How consistent is Grok 4.5 between runs?
We run every script 5 times. Grok 4.5's overall score varies by about ±2.8 points between runs, versus a board median of ±3.8. That makes it one of the steadier models we test. The full per-metric variability table is on this page.
How was Grok 4.5 evaluated?
Via xAI API using the exact model/route id grok-4.5, run on 2026-07-29. 5 runs per script, provider-default sampling, no fine-tuning; every draft scored blind with a fixed rubric by a three-family judge panel. Full details in the 'How we ran it' section and the methodology.
Is Grok 4.5 open source?
No, it is a proprietary (closed-weights) model. Among proprietary models it ranks 28th of 83 for writing.