Head to head · tested 27 Oct 2026

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: accuracy, speed and price

Similar accuracy; Gemini 3.5 Flash Lite costs less per question.

GoogleGemini 3.1 Pro Preview77.5% score · #9$0.017 per question124 tok/s

GoogleGemini 3.5 Flash Lite75.0% score · #15$0.0034 per question409 tok/s

Verdict

Built from the measurements below

Accuracy is too close to call: Gemini 3.1 Pro Preview scored 77.5% and Gemini 3.5 Flash Lite 75.0% on the same 80 questions, a gap within what chance alone could produce.
Gemini 3.5 Flash Lite is 5.1× cheaper per question as billed ($0.0034 vs $0.017), reasoning tokens included.
Gemini 3.5 Flash Lite generates text 3.3× faster: 409 tokens per second against 124.
Gemini 3.5 Flash Lite starts answering sooner: 1.1 s to the first token, against 3.4 s for Gemini 3.1 Pro Preview.

Which should you choose?

Choose Gemini 3.5 Flash Lite for the lower cost per correct answer ($0.0045 against $0.022), faster streaming and a quicker first token.

Accuracy gap +2.5 points (z = 0.37). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.

Head to head

Same questions, same prompt, same API

Measure	Gemini 3.1 Pro Preview	Gemini 3.5 Flash Lite	Edge
Verification scoreHigher is better	77.5%	75.0%	Too close to call
Cost per questionLower is better	$0.017	$0.0034	Gemini 3.5 Flash Lite
Output speedHigher is better	124	409	Gemini 3.5 Flash Lite
Time to first tokenLower is better	3.4 s	1.1 s	Gemini 3.5 Flash Lite
End-to-end response timeLower is better	8.9 s	2.8 s	Gemini 3.5 Flash Lite
Tokens per questionLower is better	1,382	1,311	Similar
Context windowHigher is better	1M	1M	Similar

Side by side

Bars are scaled to the larger of the two values. The winner on each measure is marked in bold.

Every measure

Gemini 3.1 Pro Preview first, Gemini 3.5 Flash Lite second

Verification scorehigher is better

Gemini 3.1 Pro Preview77.5%

Gemini 3.5 Flash Lite75.0%

Cost per questionlower is better

Gemini 3.1 Pro Preview$0.017

Gemini 3.5 Flash Lite$0.0034

Output speedhigher is better

Gemini 3.1 Pro Preview124

Gemini 3.5 Flash Lite409

Time to first tokenlower is better

Gemini 3.1 Pro Preview3.4 s

Gemini 3.5 Flash Lite1.1 s

End-to-end response timelower is better

Gemini 3.1 Pro Preview8.9 s

Gemini 3.5 Flash Lite2.8 s

Tokens per questionlower is better

Gemini 3.1 Pro Preview1,382

Gemini 3.5 Flash Lite1,311

Context windowhigher is better

Gemini 3.1 Pro Preview1M

Gemini 3.5 Flash Lite1M

Score vs. cost per question

Both models in color, every other model in grey

Results by subject and dataset

Questions answered correctly. Small samples: a gap of one or two questions is noise.

Subject	Questions	Gemini 3.1 Pro Preview	Gemini 3.5 Flash Lite
Science	30	26/30	23/30
Engineering	15	10/15	10/15
Medicine	11	7/11	7/11
Economics	9	8/9	7/9
Law	6	3/6	4/6
Humanities & social science	9	8/9	9/9
SuperGPQA dataset	50	36/50	33/50
MMLU-Pro dataset	30	26/30	27/30

Specifications and pricing

From OpenRouter's catalogue, plus our test dates

Specification	Gemini 3.1 Pro Preview	Gemini 3.5 Flash Lite
Creator	Google	Google
Released	19 Feb 2026	21 Jul 2026
Weights	—	—
Reasoning	Yes	Yes
Input	audio, file, image, text, video	text, image, video, file, audio
Output	text	text
Context window	1M tokens	1M tokens
Knowledge cutoff	—	—
List price in / out per 1M	$2 / $12	$0.3 / $2.5
Blended price per 1M (3:1)	$4.50	$0.85
Cheapest host	Google · $1 / $6	Google · $0.15 / $1.25
Hosts on OpenRouter	2	2
Last tested	26 Oct 2026	26 Oct 2026

Compare any two models →

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: frequently asked questions

Is Gemini 3.1 Pro Preview better than Gemini 3.5 Flash Lite?: On accuracy they are statistically tied: Gemini 3.1 Pro Preview scored 77.5% and Gemini 3.5 Flash Lite 75.0% on the same 80 questions from open datasets. Similar accuracy; Gemini 3.5 Flash Lite costs less per question.
Which is cheaper, Gemini 3.1 Pro Preview or Gemini 3.5 Flash Lite?: Gemini 3.5 Flash Lite is cheaper: $0.0034 per question as billed, against $0.017. List prices: Gemini 3.1 Pro Preview $2 in / $12 out, Gemini 3.5 Flash Lite $0.3 in / $2.5 out per million tokens.
Which is faster, Gemini 3.1 Pro Preview or Gemini 3.5 Flash Lite?: Gemini 3.5 Flash Lite is faster at 409 output tokens per second, against 124. Time to first token: 3.4 s for Gemini 3.1 Pro Preview, 1.1 s for Gemini 3.5 Flash Lite.
Which has the larger context window, Gemini 3.1 Pro Preview or Gemini 3.5 Flash Lite?: Both accept about the same amount of context: 1M and 1M tokens.

Measure

Gemini 3.1 Pro Preview

Gemini 3.5 Flash Lite

Edge

Verification scoreHigher is better

77.5%

75.0%

Too close to call

Cost per questionLower is better

$0.017

$0.0034

Gemini 3.5 Flash Lite

Output speedHigher is better

124

409

Gemini 3.5 Flash Lite

Time to first tokenLower is better

3.4 s

1.1 s

Gemini 3.5 Flash Lite

End-to-end response timeLower is better

8.9 s

2.8 s

Gemini 3.5 Flash Lite

Tokens per questionLower is better

1,382

1,311

Similar

Context windowHigher is better

Similar

Subject

Questions

Gemini 3.1 Pro Preview

Gemini 3.5 Flash Lite

Science

26/30

23/30

Engineering

10/15

Medicine

7/11

Economics

8/9

7/9

Law

3/6

4/6

Humanities & social science

8/9

9/9

SuperGPQA dataset

36/50

33/50

MMLU-Pro dataset

26/30

27/30

Specification

Gemini 3.1 Pro Preview

Gemini 3.5 Flash Lite

Creator

Google

Released

19 Feb 2026

21 Jul 2026

Weights

—

Reasoning

Yes

Input

audio, file, image, text, video

text, image, video, file, audio

Output

text

Context window

1M tokens

Knowledge cutoff

—

List price in / out per 1M

$2 / $12

$0.3 / $2.5

Blended price per 1M (3:1)

$4.50

$0.85

Cheapest host

Google · $1 / $6

Google · $0.15 / $1.25

Hosts on OpenRouter

Last tested

26 Oct 2026

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: frequently asked questions

Is Gemini 3.1 Pro Preview better than Gemini 3.5 Flash Lite?

On accuracy they are statistically tied: Gemini 3.1 Pro Preview scored 77.5% and Gemini 3.5 Flash Lite 75.0% on the same 80 questions from open datasets. Similar accuracy; Gemini 3.5 Flash Lite costs less per question.

Which is cheaper, Gemini 3.1 Pro Preview or Gemini 3.5 Flash Lite?

Gemini 3.5 Flash Lite is cheaper: $0.0034 per question as billed, against $0.017. List prices: Gemini 3.1 Pro Preview $2 in / $12 out, Gemini 3.5 Flash Lite $0.3 in / $2.5 out per million tokens.

Which is faster, Gemini 3.1 Pro Preview or Gemini 3.5 Flash Lite?

Gemini 3.5 Flash Lite is faster at 409 output tokens per second, against 124. Time to first token: 3.4 s for Gemini 3.1 Pro Preview, 1.1 s for Gemini 3.5 Flash Lite.

Which has the larger context window, Gemini 3.1 Pro Preview or Gemini 3.5 Flash Lite?

Both accept about the same amount of context: 1M and 1M tokens.

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: accuracy, speed and price

Verdict

Which should you choose?

Head to head

Side by side

Every measure

Score vs. cost per question

Results by subject and dataset

Specifications and pricing

Related comparisons

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: frequently asked questions

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: accuracy, speed and price

Verdict

Which should you choose?

Head to head

Side by side

Every measure

Score vs. cost per question

Results by subject and dataset

Specifications and pricing

Related comparisons

Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite: frequently asked questions