Comparisons

Gemini 3.5 Flash vs OpenAI GPT-OSS 20B

On provider list prices, OpenAI GPT-OSS 20B costs $0.05 per million input tokens against $1.50 for Gemini 3.5 Flash: 30.0x apart. Output is $0.20 against $9 (45.0x). On Allocate both bill at list plus the 7% transaction fee.

Gemini 3.5 Flash OpenAI GPT-OSS 20B
LabGoogleOpenAI
AccessAPI onlyOpen weights
Context window1M tokens128K tokens
List price, input$1.5 / M tokens$0.05 / M tokens
List price, output$9 / M tokens$0.2 / M tokens
Cached inputn/an/a
LicenseProprietary APIApache 2.0
Fine-tunableNoYes

Specifications and provider list prices from the Allocate catalog, checked 2026-07-08. Billed price is list plus the 7% transaction fee.

What the numbers say

Take 1,000,000 requests a month at 1,200 input and 350 output tokens each. That workload costs $130 a month on OpenAI GPT-OSS 20B and $4,950 on Gemini 3.5 Flash at list: a gap of $4,820, or 38.1x.

Gemini 3.5 Flash reads 1M tokens per request against 128K for OpenAI GPT-OSS 20B, 7.6x the window. That decides which one can take whole documents without splitting them.

OpenAI GPT-OSS 20B$0.05$0.20
Gemini 3.5 Flash$1.50$9
InputOutput

Choose Gemini 3.5 Flash for

  • High-volume support and triage
  • Document extraction at scale
  • Vision and OCR pipelines
Gemini 3.5 Flash details

Choose OpenAI GPT-OSS 20B for

  • The lower list price ($0.05 in / $0.20 out per M tokens)
  • Open weights you can fine-tune and own
  • Fine-tuning under a permissive license (Apache 2.0)
OpenAI GPT-OSS 20B details

Common questions

Which is cheaper, Gemini 3.5 Flash or OpenAI GPT-OSS 20B?

OpenAI GPT-OSS 20B, on this workload shape. At list prices it is $0.05/$0.20 per million tokens in and out against $1.50/$9 for Gemini 3.5 Flash. Billed on Allocate: $0.053/$0.21 against $1.60/$9.63, list plus 7%.

Which has the bigger context window?

Gemini 3.5 Flash: 1,000,000 tokens (1M) against 131,072 (128K) for OpenAI GPT-OSS 20B.

Can I fine-tune Gemini 3.5 Flash or OpenAI GPT-OSS 20B?

OpenAI GPT-OSS 20B publishes open weights (Apache 2.0) and can be fine-tuned on your own data. Gemini 3.5 Flash is a closed model served over API; its weights are not available.

Related comparisons

Run the numbers on your workload

Or don’t choose. On Allocate a route name is the contract: point yours at one model today, swap to the other tomorrow, and compare them on your live traffic with per-token metering.