Claude Sonnet 5 vs Gemini 3.1 Pro
Claude Sonnet 5 is the cheaper of the two, at 1.1x less on a blended 3:1 input-to-output rate. Claude Sonnet 5 runs $2.00 in / $10.00 out per 1M tokens; Gemini 3.1 Pro runs $2.00 in / $12.00 out.
On the heaviest scenario below, that gap is $200.00 a month ($2,400 a year) for identical volume. Verified 2026-08-16.
Side by side
| Claude Sonnet 5 | Gemini 3.1 Pro | |
|---|---|---|
| Provider | Anthropic | |
| Input per 1M tokens | $2.00 | $2.00 |
| Output per 1M tokens | $10.00 | $12.00 |
| Cached input per 1M | $0.20 | Not offered |
| Batch discount | 50% | 50% |
| Output-to-input ratio | 5.0x | 6.0x |
| Blended per 1M (3:1) | $4.00 | $4.50 |
What each costs on the same workload
Rate cards are hard to compare directly because the input:output mix changes the answer. These four scenarios hold the workload fixed and vary only the model, with no caching or batch discount applied to either side.
| Workload | Claude Sonnet 5 | Gemini 3.1 Pro | Monthly difference | Cheaper |
|---|---|---|---|---|
| Support chatbot 50,000 conversations/month at 3K input and 500 output tokens each | $550.00 | $600.00 | $50.00 | Claude Sonnet 5 |
| RAG document search 200,000 queries/month at 6K retrieved-context input and 400 output tokens | $3,200 | $3,360 | $160.00 | Claude Sonnet 5 |
| Coding agent 5,000 runs/month at 60K input and 8K output tokens per run | $1,000 | $1,080 | $80.00 | Claude Sonnet 5 |
| Bulk classification 5,000,000 items/month at 400 input and 20 output tokens each | $5,000 | $5,200 | $200.00 | Claude Sonnet 5 |
Which should you actually pick?
Claude Sonnet 5 matches on input and is cheaper on output, so on price alone it wins regardless of your token mix. That does not automatically make it the right call: these are different models with different capability profiles, and paying 1.1x more is justified whenever the more expensive model gets the task right on the first attempt and the cheaper one needs two or three tries, or needs human correction downstream.
Discounts can also flip the arithmetic. Prompt caching is the bigger lever of the two for anything that resends a stable prefix: see the prompt caching savings calculator. If the work is latency-tolerant, the batch API savings calculator is worth a look before you decide.
Claude Sonnet 5 vs Gemini 3.1 Pro: common questions
Is Claude Sonnet 5 or Gemini 3.1 Pro cheaper?
Claude Sonnet 5 is cheaper overall, at 1.1x less on a blended 3:1 input-to-output rate ($4.00 vs $4.50 per 1M blended tokens). It matches on input and is cheaper on output.
What is the price difference between Claude Sonnet 5 and Gemini 3.1 Pro on a real workload?
On the bulk classification scenario (5,000,000 items/month at 400 input and 20 output tokens each), Claude Sonnet 5 costs $5,000 a month and Gemini 3.1 Pro costs $5,200. That is a difference of $200.00 a month, or $2,400 a year, for the same volume of work.
Does Claude Sonnet 5 or Gemini 3.1 Pro have better discounts?
Claude Sonnet 5 offers cached input at $0.20 and a 50% batch discount. Gemini 3.1 Pro has no published cached-input rate and a 50% batch discount. On cache-heavy or latency-tolerant workloads these can matter more than the headline rate.
Should I switch from Gemini 3.1 Pro to Claude Sonnet 5?
Only if the cheaper model actually does the job. Price is the easy half of the decision; the hard half is whether output quality holds on your task. Run both against a sample of real traffic, then use the model switching savings calculator to put a number on the annual difference before committing.