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Gemini 2.5 Pro vs Gemini 3.1 Flash Lite

Close to a tie overall. Gemini 3.1 Flash Lite costs 84% less for the same work, and both read a 1M-token context.

Gemini 2.5 Pro

by Google · #44 of 67 overall

Coming soon · price at launch
Context
1M
Input / 1M
$1.25
Output / 1M
$10.00

Gemini 3.1 Flash Lite

by Google · #46 of 67 overall

Coming soon · price at launch
Context
1M
Input / 1M
$0.25
Output / 1M
$1.50

Better overall

About even

Grade 55.6 vs 54.4

Cheaper

Gemini 3.1 Flash Lite

84% less, $0.56 vs $3.44 blended

Larger context

Same

1M vs 1M tokens

Head to head

Public benchmarks. Longer is better; each value links to its source.

LMArena TextElo-style rating · LMArena (CC BY 4.0) · Oct 15, 2026
Gemini 2.5 ProGemini 2.5 Pro: 1,445
Gemini 3.1 Flash LiteGemini 3.1 Flash Lite: 1,433
LMArena WebDevElo-style rating · LMArena (CC BY 4.0) · Oct 13, 2026
Gemini 2.5 ProGemini 2.5 Pro: 1,226
Gemini 3.1 Flash LiteGemini 3.1 Flash Lite: 1,256
LMArena CodingElo-style rating · LMArena (CC BY 4.0) · Oct 15, 2026
Gemini 2.5 ProGemini 2.5 Pro: 1,464
Gemini 3.1 Flash LiteGemini 3.1 Flash Lite: 1,458
SWE-bench Verified% of issues resolved · SWE-bench · reference
Gemini 3.1 Flash LiteGemini 3.1 Flash Lite: —

Gemini 2.5 ProGemini 3.1 Flash Litev = reported by the model’s maker. — = no public score yet. Arena bars span the range across every model we grade.

What it costs you

Drag to match your monthly usage.

Gemini 2.5 Pro$650 /month
Gemini 3.1 Flash Lite$110 /month

Gemini 3.1 Flash Lite saves you $540 a month at this usage, $6,480 a year.

At a glance

AttributeGemini 2.5 ProGemini 3.1 Flash Lite
Made byGoogleGoogle
AvailabilityComing soonComing soon
Overall gradeStrong · 55.6Good · 54.4
Overall rank#44 of 67#46 of 67
Input price$1.25 per 1M$0.25 per 1M
Output price$10.00 per 1M$1.50 per 1M
Context window1,000,000 tokens1,000,000 tokens
Reasoning levelsYesYes
Reads imagesYesYes
Model IDgemini-2.5-progemini-3.1-flash-lite

Try both with one key

Same endpoint, same key, both hosted in the USA. Change one word to switch models, in Claude Code, Cursor, Cline or your own code.

Get your API key
# Ask either model the same thing
curl https://fullsendai.com/v1/chat/completions \
  -H "Authorization: Bearer $FULLSEND_API_KEY" \
  -d '{"model": "gemini-2.5-pro", "messages": [...]}'

# …then swap one word
  -d '{"model": "gemini-3.1-flash-lite", "messages": [...]}'

Questions

Is Gemini 2.5 Pro or Gemini 3.1 Flash Lite better?

They grade within two points of each other (55.6 and 54.4), so pick on price and the benchmarks that match your work.

Which is cheaper, Gemini 2.5 Pro or Gemini 3.1 Flash Lite?

Gemini 3.1 Flash Lite: $0.25 in and $1.50 out per million tokens, against $1.25 and $10.00 through FullsendAI.

Which has the larger context window?

Neither: both take 1,000,000 tokens.

Can I use both with one API key?

Yes, once they launch: both are coming soon, at the prices shown, and both will use the same FullsendAI key.

Model rankingsAll benchmarksCompare other models

Scores: LMArena (CC BY 4.0), SWE-bench, and model makers’ published results where marked v. Prices are FullsendAI’s, per million tokens. Data as of Oct 28, 2026.