GPT-5.1 vs GLM-5.1
OpenAI against Z.ai (GLM), costed on the same three workloads. GLM-5.1 is cheaper on all three workloads.
Monthly bill, side by side
| Workload | GPT-5.1 | GLM-5.1 | Difference |
|---|---|---|---|
| Support chatbot 2,500 six-turn conversations a day |
$6,553 | $4,586 | $1,968 (+43%) |
| Document summariser 1,000 single-shot summaries a day |
$698 | $618 | $79.50 (+13%) |
| Coding agent 200 twelve-turn sessions a day |
$4,185 | $3,463 | $722 (+21%) |
No prompt caching and no batch discount on either side, so the comparison is like for like. Both figures assume 30 days a month.
The rate cards
| GPT-5.1 | GLM-5.1 | |
|---|---|---|
| Input, per 1M tokens | $1.25 | $1.4 |
| Output, per 1M tokens | $10 | $4.4 |
| Cached input | $0.125 | $0.26 |
| Context window | 272K | 200K |
| Maximum output | 128K | 128K |
| Reasoning model | yes | yes |
| Vision | yes | no |
Run this comparison on your own numbers
Full detail: GPT-5.1 pricing · GLM-5.1 pricing