Gemini 2.5 Flash vs GPT-5
Complete pricing and performance comparison between Google's Gemini 2.5 Flash and OpenAI's GPT-5.
Quick Verdict
Cheaper
Gemini 2.5 Flash
4.2x cheaper input, 4.0x cheaper output
Larger Context
Gemini 2.5 Flash
1.0M vs 400K
Higher Quality
GPT-5
Score: 45 vs 21
Faster
Gemini 2.5 Flash
231 vs 101 tok/s
Pricing Comparison
| Spec | Gemini 2.5 Flash | GPT-5 | Difference |
|---|---|---|---|
| Provider | OpenAI | ||
| Input / 1M tokens | $0.3 | $1.25 | Gemini 2.5 Flash is 76% more expensive |
| Output / 1M tokens | $2.5 | $10 | Gemini 2.5 Flash is 75% more expensive |
| Context Window | 1.0M | 400K | 3x difference |
| Max Output | 66K | 16K | |
| Tokenizer | cl100k_base | o200k_base |
Performance Benchmarks
| Metric | Gemini 2.5 Flash | GPT-5 | Winner |
|---|---|---|---|
| Quality Index | 21 | 45 | GPT-5 |
| Output Speed | 231 tok/s | 101 tok/s | Gemini 2.5 Flash |
| Time to First Token | 0.42s | 78.59s | Gemini 2.5 Flash |
| Value (Quality/$) | 68.7 | 35.7 | 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 | GPT-5 | Savings |
|---|---|---|---|
Single request 1K in / 300 out | $0.0010 | $0.0042 | Gemini 2.5 Flash saves $0.0032 |
10 requests 10K in / 3K out | $0.010 | $0.042 | Gemini 2.5 Flash saves $0.032 |
100 requests 100K in / 30K out | $0.105 | $0.425 | Gemini 2.5 Flash saves $0.320 |
1,000 requests 1M in / 300K out | $1.05 | $4.25 | Gemini 2.5 Flash saves $3.20 |
10,000 requests 10M in / 3M out | $10.50 | $42.50 | Gemini 2.5 Flash saves $32.00 |
1M requests/mo 1B in / 300M out | $1050.00 | $4250.00 | Gemini 2.5 Flash saves $3200.00 |
Pros & Cons
Gemini 2.5 Flash Strengths
- +Cheaper input tokens
- +Cheaper output tokens
- +Larger context window (1.0M vs 400K)
- +Higher max output tokens
- +Faster output (231 vs 101 tok/s)
- +Lower latency (faster first token)
GPT-5 Strengths
- +Higher quality score (45 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
- →Generating long-form content or detailed code
- →Real-time applications, chat, or autocomplete
Choose GPT-5 for
- →Tasks requiring maximum accuracy and reasoning
Frequently Asked Questions
Which is cheaper, Gemini 2.5 Flash or GPT-5?
For input tokens, Gemini 2.5 Flash is 4.2x cheaper at $0.3/1M tokens. For output tokens, Gemini 2.5 Flash is 4.0x cheaper at $2.5/1M tokens. At typical usage (1M input + 300K output), Gemini 2.5 Flash costs $1.05 vs GPT-5 at $4.25.
What's the context window difference?
Gemini 2.5 Flash supports 1.0M context (1,048,576 tokens), while GPT-5 supports 400K (400,000 tokens). Gemini 2.5 Flash can handle 3x more context in a single request.
Which model has better benchmarks?
Quality Index: Gemini 2.5 Flash scores 21 vs GPT-5 at 45. Speed: Gemini 2.5 Flash generates 231 tok/s vs GPT-5 at 101 tok/s. Time to first token: Gemini 2.5 Flash at 0.42s vs GPT-5 at 78.59s.
When should I choose Gemini 2.5 Flash over GPT-5?
Choose Gemini 2.5 Flash when you need: Cheaper input tokens, Cheaper output tokens, Larger context window (1.0M vs 400K), Higher max output tokens, Faster output (231 vs 101 tok/s), Lower latency (faster first token). Choose GPT-5 when you need: Higher quality score (45 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, GPT-5 = $42.50. At 10K input + 1K output per request (longer conversations): Gemini 2.5 Flash = $55.00, GPT-5 = $225.00.
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