GPT-5.5 vs Grok 4.20
Wins 7 of 8 areas
Coding · Agents · Reasoning · Facts · Images and charts · Math · Long documents
Wins 1 of 8 areas
Following instructions
GPT-5.5 is the stronger all-rounder.Grok 4.20 is cheaper and better at following instructions.
Scores updated · 23 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 thinking40GPT-5.54 of 4 tests
- CodingWriting and fixing software20GPT-5.52 of 2 tests
- AgentsCarrying out multi-step tasks on its own20GPT-5.52 of 2 tests
- MathCompetition and research-level math20GPT-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 1 test
- Long documentsFinding answers in very long texts10GPT-5.51 of 1 test
- Following instructionsDoing exactly what it is asked01Grok 4.201 of 1 test
Images and charts, long documents and following instructions rest on a single test each.
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.
Grok 4.20 costs 89% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where GPT-5.5 pulls ahead
- Extremely hard research-level math problemsFrontierMath Tier 4+55.4points ahead
- Unpublished advanced math problemsFrontierMath Tiers 1-3 (v2)+40.4points ahead
- Short factual questions, answered correctlySimpleQA Verified+32.8points ahead
Where Grok 4.20 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+66.6points ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+7points ahead
Every test, side by side
All 23 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5.5
- Terminal-Bench HardGPT-5.5 by 19.760.640.9+19.7
- SciCodeGPT-5.5 by 11.155.844.7+11.1
AgentsGPT-5.5
- AA ApexAgentsGPT-5.5 by 23.537.714.2+23.5
- GDPValGPT-5.5 by 15.742.727+15.7
ReasoningGPT-5.5
- CritPtGPT-5.5 by 21.127.16+21.1
- ARC-AGI-2GPT-5.5 by 19.98565.1+19.9
- Humanity's Last ExamGPT-5.5 by 13.445.832.4+13.4
- GPQA DiamondGPT-5.5 by 593.588.5+5
FactsGPT-5.5
- AA-Omniscience · Non-hallucinationGrok 4.20 by 66.61177.6+66.6
- SimpleQA VerifiedGPT-5.5 by 32.86330.2+32.8
- AA-Omniscience · AccuracyGPT-5.5 by 29.15828.9+29.1
MathGPT-5.5
- FrontierMath Tier 4GPT-5.5 by 55.472.517.1+55.4
- FrontierMath Tiers 1-3 (v2)GPT-5.5 by 40.485.344.9+40.4
Other results7 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.
- Artificial Analysis Coding IndexGPT-5.5 by 32.774.942.2+32.7
- HiL-Bench (Tools-allowed)GPT-5.5 by 19.739.720+19.7
- AA Agentic IndexGrok 4.20 by 13.637.350.9+13.6
- AA IntelligenceGPT-5.5 by 13.238.425.2+13.2
- AA-OmniscienceGPT-5.5 by 7.520.512.9+7.5
- ARC-AGI-1GPT-5.5 by 5.59589.5+5.5
- τ²-Bench Telecom (AA run)Grok 4.20 by 2.693.996.5+2.6
Questions people ask
Which is better, GPT-5.5 or Grok 4.20?
GPT-5.5 wins seven of the eight areas we test: coding, agents, reasoning, facts, images and charts, math and long documents. Grok 4.20 wins following instructions, and costs 89% less.
Which is better for coding?
GPT-5.5. It wins 2 of the 2 coding tests both models report; Grok 4.20 wins none.
Which is cheaper?
GPT-5.5 costs $5.00 per million input tokens and $30.00 per million output tokens; Grok 4.20 costs $1.25 and $2.50. That makes Grok 4.20 about 89% cheaper for the same work.
How do you compare the two?
We use the 23 benchmark tests both models have published scores on. The verdict counts the 16 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 7 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.