Gemini 2.5 Pro vs Gemini 3.1 Pro
Complete pricing and performance comparison between Google's Gemini 2.5 Pro and Google's Gemini 3.1 Pro.
Quick Verdict
Cheaper
Gemini 2.5 Pro
1.6x cheaper input, 1.2x cheaper output
Larger Context
Gemini 2.5 Pro
1.0M vs 1.0M
Higher Quality
Gemini 3.1 Pro
Score: 57 vs 35
Faster
Gemini 2.5 Pro
124 vs 120 tok/s
Pricing Comparison
| Spec | Gemini 2.5 Pro | Gemini 3.1 Pro | Difference |
|---|---|---|---|
| Provider | |||
| Input / 1M tokens | $1.25 | $2 | Gemini 2.5 Pro is 38% more expensive |
| Output / 1M tokens | $10 | $12 | Gemini 2.5 Pro is 17% more expensive |
| Context Window | 1.0M | 1.0M | Same |
| Max Output | 66K | 66K |
Performance Benchmarks
| Metric | Gemini 2.5 Pro | Gemini 3.1 Pro | Winner |
|---|---|---|---|
| Quality Index | 35 | 57 | Gemini 3.1 Pro |
| Output Speed | 124 tok/s | 120 tok/s | Gemini 2.5 Pro |
| Time to First Token | 21.40s | 21.32s | Gemini 3.1 Pro |
| Value (Quality/$) | 27.7 | 28.6 | 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 Pro | Gemini 3.1 Pro | Savings |
|---|---|---|---|
Single request 1K in / 300 out | $0.0042 | $0.0056 | Gemini 2.5 Pro saves $0.0014 |
10 requests 10K in / 3K out | $0.042 | $0.056 | Gemini 2.5 Pro saves $0.014 |
100 requests 100K in / 30K out | $0.425 | $0.560 | Gemini 2.5 Pro saves $0.135 |
1,000 requests 1M in / 300K out | $4.25 | $5.60 | Gemini 2.5 Pro saves $1.35 |
10,000 requests 10M in / 3M out | $42.50 | $56.00 | Gemini 2.5 Pro saves $13.50 |
1M requests/mo 1B in / 300M out | $4250.00 | $5600.00 | Gemini 2.5 Pro saves $1350.00 |
Pros & Cons
Gemini 2.5 Pro Strengths
- +Cheaper input tokens
- +Cheaper output tokens
- +Faster output (124 vs 120 tok/s)
Gemini 3.1 Pro Strengths
- +Higher quality score (57 vs 35)
- +Lower latency (faster first token)
When to Use Each Model
Choose Gemini 2.5 Pro for
- →Budget-conscious projects where cost is the primary factor
- →Real-time applications, chat, or autocomplete
Choose Gemini 3.1 Pro for
- →Tasks requiring maximum accuracy and reasoning
Frequently Asked Questions
Which is cheaper, Gemini 2.5 Pro or Gemini 3.1 Pro?
For input tokens, Gemini 2.5 Pro is 1.6x cheaper at $1.25/1M tokens. For output tokens, Gemini 2.5 Pro is 1.2x cheaper at $10/1M tokens. At typical usage (1M input + 300K output), Gemini 2.5 Pro costs $4.25 vs Gemini 3.1 Pro at $5.60.
What's the context window difference?
Gemini 2.5 Pro supports 1.0M context (1,048,576 tokens), while Gemini 3.1 Pro supports 1.0M (1,048,576 tokens). Gemini 3.1 Pro can handle 1x more context in a single request.
Which model has better benchmarks?
Quality Index: Gemini 2.5 Pro scores 35 vs Gemini 3.1 Pro at 57. Speed: Gemini 2.5 Pro generates 124 tok/s vs Gemini 3.1 Pro at 120 tok/s. Time to first token: Gemini 2.5 Pro at 21.40s vs Gemini 3.1 Pro at 21.32s.
When should I choose Gemini 2.5 Pro over Gemini 3.1 Pro?
Choose Gemini 2.5 Pro when you need: Cheaper input tokens, Cheaper output tokens, Faster output (124 vs 120 tok/s). Choose Gemini 3.1 Pro when you need: Higher quality score (57 vs 35), Lower latency (faster first token).
How much would 10,000 API requests cost?
At 1K input + 300 output tokens per request (typical chat): Gemini 2.5 Pro = $42.50, Gemini 3.1 Pro = $56.00. At 10K input + 1K output per request (longer conversations): Gemini 2.5 Pro = $225.00, Gemini 3.1 Pro = $320.00.
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