The Known Good Updated 29 Jul 2026
OpenAI: GPT-5 Nano vs OpenAI: o3 ·OpenAI vs OpenAI

OpenAI: GPT-5 Nano vs OpenAI: o3 — head-to-head comparison

OpenAI: GPT-5 Nano profile OpenAI: o3 profile All comparisons
OpenAI: GPT-5 Nano — OpenAI
Quality
#32 of 62
67based on 4 of 7 evaluations
Known Good Index
Speed
#47 of 317
97.5
Output tokens per second
Price
#58 of 370
$0.14
Blended per 1M tokens
In $0.05 · Out $0.40
Cache hit price
#14 of 238
$0.005
per 1M tokens (−90%)
Context
#120 of 375
400k
tokens (~600 pages)
OpenAI: o3 — OpenAI
Quality
#25 of 62
74based on 5 of 7 evaluations
Known Good Index
Speed
#85 of 317
70.8
Output tokens per second
Price
#292 of 370
$3.50
Blended per 1M tokens
In $2.00 · Out $8.00
Cache hit price
#204 of 238
$0.50
per 1M tokens (−75%)
Context
#226 of 375
200k
tokens (~300 pages)
Summary

On the Known Good Index, OpenAI: GPT-5 Nano scores 67 and OpenAI: o3 scores 74 — a 6-point lead for OpenAI: o3. They share 3 published evaluations, with OpenAI: GPT-5 Nano ahead on 0 and OpenAI: o3 ahead on 3.

Blended pricing is $0.14 per 1M tokens for OpenAI: GPT-5 Nano and $3.50 for OpenAI: o3 — OpenAI: GPT-5 Nano is about 25.5× cheaper.

Throughput is 98 tokens per second for OpenAI: GPT-5 Nano and 71 for OpenAI: o3, with time to first token at 2.3s and 3.6s. OpenAI: GPT-5 Nano accepts 400k tokens of context against 200k.

OpenAI: GPT-5 Nano is proprietary; OpenAI: o3 is proprietary. 2 tracked hosts serve one or both, and 1 serve both.

Generated from tracked data on 29 Jul 2026 · how these comparisons are computed →

At a glance
MetricOpenAI: GPT-5 NanoOpenAI: o3
Known Good Index 67 based on 4 of 7 evaluations 74 based on 5 of 7 evaluations
Blended $/1M $0.14 $3.50
Output tok/s 98 71
Context window 400k 200k
Providers 2 1
Jump to section

Quality

Known Good Index and the capability indices, side by side

Index scores

Each index is min-max normalised across tracked models and scaled 0–100 from published evaluations. We do not run these evaluations.

MetricOpenAI: GPT-5 NanoOpenAI: o3
Known Good Index 67 74
Mathematics Index 89 92
Reasoning Index — 62
Agentic Index 21 60
Openness Index 5 5
The Known Good

Quality Breakdown

Every evaluation both models report a published score for

Evaluations both models report

Bar = OpenAI: GPT-5 Nano · marker = OpenAI: o3 · scores ingested from Epoch AI (CC-BY 4.0)

GPQA Diamond69 / 82
Mock AIME 2024–2581 / 84
MATH Level 595 / 98

Right-hand figures read OpenAI: GPT-5 Nano / OpenAI: o3. OpenAI: GPT-5 Nano leads on 0 of 3, OpenAI: o3 on 3.

The Known Good

Arena Elo

Human preference rating from blind pairwise votes

Arena ratings

Elo from blind pairwise votes, ingested from Arena. Higher is better.

Neither model currently appears in an arena we ingest.

The Known Good

Price & Cost

Published API pricing by token type

Published pricing

USD per 1M tokens. Blended is a 3:1 input:output mix. Live from OpenRouter, cross-checked against models.dev. Lower is better.

MetricOpenAI: GPT-5 NanoOpenAI: o3
Input $/1M $0.05 $2.00
Output $/1M $0.40 $8.00
Blended $/1M $0.14 $3.50
Cache read $/1M $0.005 $0.500
The Known Good
We publish blended price rather than cost-per-task. Cost-per-task requires token counts from an evaluation suite we do not run. Blended price is computed from published rates and is fully reproducible — see the pricing methodology.

Context Window

Maximum input accepted and maximum output emitted

Context and output limits

Provider-declared limits, from metadata via models.dev and OpenRouter. Higher is better.

MetricOpenAI: GPT-5 NanoOpenAI: o3
Context window 400k 200k
Max output tokens 128k 100k
The Known Good

Speed & Latency

Median throughput and time to first token across hosting providers

Output speedTime to first token
Throughput and latency

Medians across all tracked providers, derived from OpenRouter endpoint telemetry.

MetricOpenAI: GPT-5 NanoOpenAI: o3
Output tokens/s 98 71
Time to first token 2.3s 3.6s
The Known Good

Providers

Which hosts serve each model, and at what price and speed

2 hosts · 1 serve both
Full provider benchmarks →
Provider OpenAI: GPT-5 Nano blendedOpenAI: GPT-5 Nano tok/s OpenAI: o3 blendedOpenAI: o3 tok/s
OpenAI · first party $0.07 186 $3.50 84
Azure · first party $0.14 58 — —

Per-host pricing and telemetry from OpenRouter. A dash means that host does not serve that model.

The Known Good
Sources for this page
Pricing & providers — OpenRouter Metadata — models.dev Benchmarks — Epoch AI (CC-BY 4.0) Full attribution →