GPT-6 Astra vs GPT-5.6 Terra
Head-to-head technical comparison of intelligence, capabilities, and API pricing.
Which should you use?
GPT-6 Astra leads on the composite index by 2.8 points (96.7 vs 93.9).
Cost is the sharper difference: GPT-6 Astra is 5x the input price of GPT-5.6 Terra ($10 against $2 per 1M), so at volume the choice is usually decided by budget rather than benchmarks.
Pick GPT-6 Astra when
- Higher composite index — 96.7 against 93.9, a gap of 2.8 points.
- Ahead on Arena Elo by 26 points (1496 vs 1470), which is outside the board's published confidence intervals.
- Stronger on MMLU-Pro: 95.8% against 93.5%.
Pick GPT-5.6 Terra when
- Cheaper input tokens — $2 against $10 per 1M, so GPT-6 Astra costs 5x as much to feed.
- Better value per point of measured capability: $0.021 per index point against $0.103.
Value per point of measured capability, at list input pricing: GPT-5.6 Terra $0.021 · GPT-6 Astra $0.103 per index point. Run your own token mix through the token cost calculator — a comparison at list price ignores caching and batch discounts, which move real bills more than this gap does.
Where these numbers come from
Figures as of 2026-09-07. Arena Elo and pricing are read from the public board and each vendor's own pricing page; see the full leaderboard for all 34 models and which columns are measured rather than estimated, or the benchmark matrix for scores benchmark by benchmark.