Claude Sonnet 5.5 vs GPT-6.1 Sol
GPT-6.1 Sol leads overall, C to C-. Claude Sonnet 5.5 is about 5.0x cheaper per task. By suite, real-world issues is even at C- and spec planning is even at C+. Take Claude Sonnet 5.5 anyway when you want the side that is cheaper per task and faster on real-world issues.Measured
Each agent graded on the same private suites, running headless through its own tools. Advantages are oriented so a win is a win, whichever way the metric runs.
Verdict: GPT-6.1 Sol vs Claude Sonnet 5.5
GPT-6.1 Sol leads overall, C to C-. By suite: real-world issues is even at C- (60% vs 57% capability); spec planning is even at C+ (74% vs 73% capability); GPT-6.1 Sol takes vibe coding, C+ to D+ (72% vs 48% capability). Claude Sonnet 5.5 used <1% of Claude Max 5x's weekly limit per pass, $0.003 per task at the listed price. GPT-6.1 Sol used 6% of ChatGPT Plus's weekly limit per pass, $0.015 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.2% of ChatGPT Pro 5x's weekly limit (est, about $0.015 per task). Per task, Claude Sonnet 5.5 is about 5.0x cheaper ($0.003 vs $0.015). Claude Sonnet 5.5 is faster on real-world issues: a median task takes 37s against 3m 26s. Both finished every task on it. Reasons to pick Claude Sonnet 5.5 anyway: it is cheaper per task ($0.003 vs $0.015) and it is faster on real-world issues (37s vs 3m 26s median).
| Dimension | Claude Sonnet 5.5 | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 60% | 57% | +3% (Claude Sonnet 5.5 leads) |
| Median task time | 37s | 3m 26s | 2m 49s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.002 / task | $0.012 / task | $0.010 / task lower (Claude Sonnet 5.5 leads) |
Claude Sonnet 5.5: 4.0% of Claude Max 5x (4.0% / 5h) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-6.1 Sol: 4.0% of ChatGPT Plus (28.0% / 5h, 4.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Claude Sonnet 5.5 | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 74% | 73% | +1% (Claude Sonnet 5.5 leads) |
| Median task time | 3m 25s | 6m 22s | 2m 57s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.007 / task | $0.023 / task | $0.016 / task lower (Claude Sonnet 5.5 leads) |
Claude Sonnet 5.5: 4.0% of Claude Max 5x (4.0% / 5h) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-6.1 Sol: 2.0% of ChatGPT Plus (9.0% / 5h, 2.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Claude Sonnet 5.5 | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 48% | 72% | +23% (GPT-6.1 Sol leads) |
| Median task time | 56s | 4m 55s | 3m 58s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.001 / task | $0.018 / task | $0.017 / task lower (Claude Sonnet 5.5 leads) |
Claude Sonnet 5.5: 0.2% of Claude Max 5x (0.2% / 5h) per good solve. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-6.1 Sol: 0.4% of ChatGPT Plus (2.2% / 5h, 0.4% / 1w) per good solve. Its weekly limit holds about 6 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
Grades and deltas are comparable only within a suite version. See methodology.
Frequently asked questions
Which is better for coding, Claude Sonnet 5.5 or GPT-6.1 Sol?
Claude Sonnet 5.5 clears higher: tier 4 of 5 versus tier 2 for GPT-6.1 Sol on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-28.
Which is cheaper per task, Claude Sonnet 5.5 or GPT-6.1 Sol?
Claude Sonnet 5.5 used <1% of Claude Max 5x's weekly limit per pass, $0.003 per task at the listed price. GPT-6.1 Sol used 6% of ChatGPT Plus's weekly limit per pass, $0.015 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.2% of ChatGPT Pro 5x's weekly limit (est, about $0.015 per task). Per task, Claude Sonnet 5.5 is about 5.0x cheaper ($0.003 vs $0.015).
What do Claude Sonnet 5.5 and GPT-6.1 Sol cost a month?
Claude Sonnet 5.5 runs on Claude Max 5x at $100/month (public price as of 2026-07-20). GPT-6.1 Sol runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).