GPT-5.5 vs GPT-5.6 Terra
Wins 6 of 8 areas
Reasoning · Facts · Images and charts · Math · Long documents · Following instructions
Wins 2 of 8 areas
Coding · Agents
GPT-5.5 is the stronger all-rounder.GPT-5.6 Terra is cheaper and better at agents.
Both rank among the ten best models we track in coding and long documents.
Scores updated · 52 tests both models report · How we compare
Where each one wins
Tests won in each of the eight areas we test. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- ReasoningHard problems that need careful thinking41GPT-5.54 of 7 tests · 2 ties
- MathCompetition and research-level math20GPT-5.52 of 3 tests · 1 tie
- Following instructionsDoing exactly what it is asked20GPT-5.52 of 2 tests
- FactsGetting facts right instead of making them up21GPT-5.52 of 3 tests
- Images and chartsUnderstanding pictures, charts and video10GPT-5.51 of 2 tests · 1 tie
- Long documentsFinding answers in very long texts10GPT-5.51 of 1 test
- AgentsCarrying out multi-step tasks on its own06GPT-5.6 Terra6 of 6 tests
- CodingWriting and fixing software23GPT-5.6 Terra3 of 7 tests · 2 ties
Long documents rests on a single test.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
GPT-5.6 Terra costs 60% less for the same work.
The biggest differences
The three tests each model wins by the widest margin. Scores are out of 100.
Where GPT-5.5 pulls ahead
- Common-sense trick questionsSimpleBench+20.1points ahead
- Short factual questions, answered correctlySimpleQA Verified+19.8points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+11.2points ahead
Where GPT-5.6 Terra pulls ahead
- Complex command-line tasks across many fieldsTerminal-Bench 4.0+20.8points ahead
- Finds the root cause of IT system incidentsAA IT-Bench SRE+5.2points ahead
- Real work tasks from 44 professionsGDPVal+5points ahead
Every test, side by side
All 52 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5.6 Terra
- SWE-bench ProGPT-5.6 Terra by 4.858.663.4+4.8
- LiveBench · CodingGPT-5.5 by 3.982.278.3+3.9
- Terminal-Bench 2.1GPT-5.6 Terra by 3.784.388+3.7
- Terminal-Bench HardGPT-5.5 by 360.657.6+3
- LiveBench · Agentic CodingGPT-5.6 Terra by 15455+1
- LMArena · WebDevtie15131522tie
- SciCodetie55.855tie
AgentsGPT-5.6 Terra
- Terminal-Bench 4.0GPT-5.6 Terra by 20.814.635.4+20.8
- AA IT-Bench SREGPT-5.6 Terra by 5.245.851+5.2
- GDPValGPT-5.6 Terra by 542.747.7+5
- BrowseCompGPT-5.6 Terra by 3.184.487.5+3.1
- AA ApexAgentsGPT-5.6 Terra by 1.237.738.9+1.2
- τ-Bench V3 · BankingGPT-5.6 Terra by 1.23940.2+1.2
ReasoningGPT-5.5
- SimpleBenchGPT-5.5 by 20.16948.9+20.1
- CritPtGPT-5.6 Terra by 2.927.130+2.9
- Humanity's Last ExamGPT-5.5 by 2.945.842.9+2.9
- ARC-AGI-2GPT-5.5 by 1.18583.9+1.1
- GPQA DiamondGPT-5.5 by 193.592.5+1
- LiveBench · Reasoningtie89.790.6tie
- ARC-AGI-3tie0.40.8tie
FactsGPT-5.5
- SimpleQA VerifiedGPT-5.5 by 19.86343.2+19.8
- AA-Omniscience · AccuracyGPT-5.5 by 11.25846.8+11.2
- AA-Omniscience · Non-hallucinationGPT-5.6 Terra by 1.11112.1+1.1
Images and chartsGPT-5.5
- LMArena · VisionGPT-5.5 by 21 rating points12921271+21 rating
- MMMU-Protie79.980.7tie
MathGPT-5.5
- FrontierMath Tier 4GPT-5.5 by 4.272.568.3+4.2
- LiveBench · MathematicsGPT-5.5 by 195.994.9+1
- FrontierMath Tiers 1-3 (v2)tie85.386tie
Following instructionsGPT-5.5
- LiveBench · Instruction FollowingGPT-5.5 by 6.170.764.6+6.1
- IFBenchGPT-5.5 by 4.775.971.2+4.7
Other results21 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- FrontierMath (overall)GPT-5.6 Terra by 49.535.484.9+49.5
- Agents' Last ExamGPT-5.6 Terra by 23.826.650.4+23.8
- AA-OmniscienceGPT-5.5 by 20.420.50.1+20.4
- τ²-Bench Telecom (AA run)GPT-5.5 by 7.693.986.3+7.6
- AA Agentic IndexGPT-5.6 Terra by 6.437.343.7+6.4
- HealthBench ProfessionalGPT-5.6 Terra by 5.951.857.7+5.9
- HealthBench Professional length-adjustedGPT-5.6 Terra by 5.951.857.7+5.9
- livebench_languageGPT-5.5 by 4.587.482.9+4.5
- AA IntelligenceGPT-5.6 Terra by 3.738.442.1+3.7
- GDPval-AA v2 EloGPT-5.6 Terra by 37 rating points14911528+37 rating
- DeepSWE 1.1GPT-5.6 Terra by 36770+3
- ToolathlonGPT-5.5 by 2.555.653.1+2.5
- livebench_data_analysisGPT-5.5 by 2.381.679.3+2.3
- Artificial Analysis Coding IndexGPT-5.6 Terra by 1.874.976.7+1.8
- ARC-AGI-1GPT-5.6 Terra by 1.59596.5+1.5
- HealthBench Hard length-adjustedGPT-5.6 Terra by 1.231.532.7+1.2
- HealthBenchtie56.557tie
- HealthBench Consensus length-adjustedtie95.695.1tie
- HealthBench length-adjustedtie56.557tie
- DeepSWEtie7069.6tie
- GDP (Surge AI)tie24.924.7tie
Questions people ask
Which is better, GPT-5.5 or GPT-5.6 Terra?
GPT-5.5 wins six of the eight areas we test: reasoning, facts, images and charts, math, long documents and following instructions. GPT-5.6 Terra wins coding and agents, and costs 60% less.
Which is better for coding?
GPT-5.6 Terra. It wins 3 of the 7 coding tests both models report; GPT-5.5 wins 2, and 2 are ties.
Which is cheaper?
GPT-5.5 costs $5.00 per million input tokens and $30.00 per million output tokens; GPT-5.6 Terra costs $2.00 and $12.00. That makes GPT-5.6 Terra about 60% cheaper for the same work.
How do you compare the two?
We use the 52 benchmark tests both models have published scores on. The verdict counts the 31 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 21 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.