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Gemini 2.5 Pro vs Gemini 3.1 Flash-Lite

Complete pricing and performance comparison between Google's Gemini 2.5 Pro and Google's Gemini 3.1 Flash-Lite.

Quick Verdict

Cheaper
Gemini 3.1 Flash-Lite
5.0x cheaper input, 6.7x cheaper output
Larger Context
Gemini 2.5 Pro
1.0M vs 1.0M
Higher Quality
Gemini 2.5 Pro
Score: 35 vs 34
Faster
Gemini 3.1 Flash-Lite
230 vs 124 tok/s

Pricing Comparison

SpecGemini 2.5 ProGemini 3.1 Flash-LiteDifference
ProviderGoogleGoogle
Input / 1M tokens$1.25$0.25Gemini 3.1 Flash-Lite is 80% more expensive
Output / 1M tokens$10$1.5Gemini 3.1 Flash-Lite is 85% more expensive
Context Window1.0M1.0MSame
Max Output66K66K

Performance Benchmarks

MetricGemini 2.5 ProGemini 3.1 Flash-LiteWinner
Quality Index3534Gemini 2.5 Pro
Output Speed124 tok/s230 tok/sGemini 3.1 Flash-Lite
Time to First Token21.40s5.17sGemini 3.1 Flash-Lite
Value (Quality/$)27.7134.0Higher = 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).

UsageGemini 2.5 ProGemini 3.1 Flash-LiteSavings
Single request
1K in / 300 out
$0.0042$0.0007Gemini 3.1 Flash-Lite saves $0.0035
10 requests
10K in / 3K out
$0.042$0.0070Gemini 3.1 Flash-Lite saves $0.035
100 requests
100K in / 30K out
$0.425$0.070Gemini 3.1 Flash-Lite saves $0.355
1,000 requests
1M in / 300K out
$4.25$0.700Gemini 3.1 Flash-Lite saves $3.55
10,000 requests
10M in / 3M out
$42.50$7.00Gemini 3.1 Flash-Lite saves $35.50
1M requests/mo
1B in / 300M out
$4250.00$700.00Gemini 3.1 Flash-Lite saves $3550.00

Pros & Cons

Gemini 2.5 Pro Strengths

  • +Higher quality score (35 vs 34)

Gemini 3.1 Flash-Lite Strengths

  • +Cheaper input tokens
  • +Cheaper output tokens
  • +Faster output (230 vs 124 tok/s)
  • +Lower latency (faster first token)

When to Use Each Model

Choose Gemini 2.5 Pro for

  • →Tasks requiring maximum accuracy and reasoning

Choose Gemini 3.1 Flash-Lite for

  • →Budget-conscious projects where cost is the primary factor
  • →Real-time applications, chat, or autocomplete

Frequently Asked Questions

Which is cheaper, Gemini 2.5 Pro or Gemini 3.1 Flash-Lite?
For input tokens, Gemini 3.1 Flash-Lite is 5.0x cheaper at $0.25/1M tokens. For output tokens, Gemini 3.1 Flash-Lite is 6.7x cheaper at $1.5/1M tokens. At typical usage (1M input + 300K output), Gemini 2.5 Pro costs $4.25 vs Gemini 3.1 Flash-Lite at $0.700.
What's the context window difference?
Gemini 2.5 Pro supports 1.0M context (1,048,576 tokens), while Gemini 3.1 Flash-Lite supports 1.0M (1,048,576 tokens). Gemini 3.1 Flash-Lite 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 Flash-Lite at 34. Speed: Gemini 2.5 Pro generates 124 tok/s vs Gemini 3.1 Flash-Lite at 230 tok/s. Time to first token: Gemini 2.5 Pro at 21.40s vs Gemini 3.1 Flash-Lite at 5.17s.
When should I choose Gemini 2.5 Pro over Gemini 3.1 Flash-Lite?
Choose Gemini 2.5 Pro when you need: Higher quality score (35 vs 34). Choose Gemini 3.1 Flash-Lite when you need: Cheaper input tokens, Cheaper output tokens, Faster output (230 vs 124 tok/s), 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 Flash-Lite = $7.00. At 10K input + 1K output per request (longer conversations): Gemini 2.5 Pro = $225.00, Gemini 3.1 Flash-Lite = $40.00.

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Gemini 2.5 Pro DetailsGemini 3.1 Flash-Lite DetailsFull Pricing TableCost Calculator