Gemini 2.5 Flash vs o3
Complete pricing and performance comparison between Google's Gemini 2.5 Flash and OpenAI's o3.
Quick Verdict
Cheaper
Gemini 2.5 Flash
6.7x cheaper input, 3.2x cheaper output
Larger Context
Gemini 2.5 Flash
1.0M vs 200K
Higher Quality
o3
Score: 38 vs 21
Faster
Gemini 2.5 Flash
231 vs 117 tok/s
Pricing Comparison
| Spec | Gemini 2.5 Flash | o3 | Difference |
|---|---|---|---|
| Provider | OpenAI | ||
| Input / 1M tokens | $0.3 | $2 | Gemini 2.5 Flash is 85% more expensive |
| Output / 1M tokens | $2.5 | $8 | Gemini 2.5 Flash is 69% more expensive |
| Context Window | 1.0M | 200K | 5x difference |
| Max Output | 66K | 100K | |
| Tokenizer | cl100k_base | o200k_base |
Performance Benchmarks
| Metric | Gemini 2.5 Flash | o3 | Winner |
|---|---|---|---|
| Quality Index | 21 | 38 | o3 |
| Output Speed | 231 tok/s | 117 tok/s | Gemini 2.5 Flash |
| Time to First Token | 0.42s | 8.94s | Gemini 2.5 Flash |
| Value (Quality/$) | 68.7 | 19.2 | Higher = better value |
Benchmark data from Artificial Analysis. Quality Index is a composite score across reasoning, coding, and knowledge tasks.
Cost at Scale
Estimated cost at different usage levels (3:1 input-to-output token ratio, typical for chat).
| Usage | Gemini 2.5 Flash | o3 | Savings |
|---|---|---|---|
Single request 1K in / 300 out | $0.0010 | $0.0044 | Gemini 2.5 Flash saves $0.0033 |
10 requests 10K in / 3K out | $0.010 | $0.044 | Gemini 2.5 Flash saves $0.034 |
100 requests 100K in / 30K out | $0.105 | $0.440 | Gemini 2.5 Flash saves $0.335 |
1,000 requests 1M in / 300K out | $1.05 | $4.40 | Gemini 2.5 Flash saves $3.35 |
10,000 requests 10M in / 3M out | $10.50 | $44.00 | Gemini 2.5 Flash saves $33.50 |
1M requests/mo 1B in / 300M out | $1050.00 | $4400.00 | Gemini 2.5 Flash saves $3350.00 |
Pros & Cons
Gemini 2.5 Flash Strengths
- +Cheaper input tokens
- +Cheaper output tokens
- +Larger context window (1.0M vs 200K)
- +Faster output (231 vs 117 tok/s)
- +Lower latency (faster first token)
o3 Strengths
- +Higher max output tokens
- +Higher quality score (38 vs 21)
When to Use Each Model
Choose Gemini 2.5 Flash for
- →Budget-conscious projects where cost is the primary factor
- →Long documents, large codebases, or multi-turn conversations
- →Real-time applications, chat, or autocomplete
Choose o3 for
- →Generating long-form content or detailed code
- →Tasks requiring maximum accuracy and reasoning
Frequently Asked Questions
Which is cheaper, Gemini 2.5 Flash or o3?
For input tokens, Gemini 2.5 Flash is 6.7x cheaper at $0.3/1M tokens. For output tokens, Gemini 2.5 Flash is 3.2x cheaper at $2.5/1M tokens. At typical usage (1M input + 300K output), Gemini 2.5 Flash costs $1.05 vs o3 at $4.40.
What's the context window difference?
Gemini 2.5 Flash supports 1.0M context (1,048,576 tokens), while o3 supports 200K (200,000 tokens). Gemini 2.5 Flash can handle 5x more context in a single request.
Which model has better benchmarks?
Quality Index: Gemini 2.5 Flash scores 21 vs o3 at 38. Speed: Gemini 2.5 Flash generates 231 tok/s vs o3 at 117 tok/s. Time to first token: Gemini 2.5 Flash at 0.42s vs o3 at 8.94s.
When should I choose Gemini 2.5 Flash over o3?
Choose Gemini 2.5 Flash when you need: Cheaper input tokens, Cheaper output tokens, Larger context window (1.0M vs 200K), Faster output (231 vs 117 tok/s), Lower latency (faster first token). Choose o3 when you need: Higher max output tokens, Higher quality score (38 vs 21).
How much would 10,000 API requests cost?
At 1K input + 300 output tokens per request (typical chat): Gemini 2.5 Flash = $10.50, o3 = $44.00. At 10K input + 1K output per request (longer conversations): Gemini 2.5 Flash = $55.00, o3 = $280.00.