Short verdict
Neither brand wins an arithmetic task by producing a longer explanation. Compare whether ChatGPT Free or DeepSeek exposes its inputs, notices missing assumptions and accepts a correction at the right step. Verify the numerical result independently and use the current account limits rather than a fixed quota claim.
ChatGPT Free vs DeepSeek is often framed as a contest between model names. For a practical arithmetic task, a better comparison asks which service makes an error easier to find. A model selection or a “reasoning” label is not evidence that a particular answer is correct.
The checklist below is an original evaluation method. Official service information was checked on October 8, 2026. We did not run matched model tests, so this article makes no accuracy or speed ranking.
Establish the answer before comparing explanations
Use a fictional printing order: 120 cards at $0.35 each, a fixed $6 setup fee, and a 5% discount on the cards only. With no taxes or other charges in the example, the expected total is $45.90: $42 minus $2.10 plus $6.
Check that independently first. Then give both assistants the identical problem. Request the input list, calculation and assumptions in a short response. This prevents attractive prose from becoming the scoring standard.
| Criterion | A useful response does this |
|---|---|
| Input fidelity | Keeps 120 cards and the stated unit price |
| Scope | Discounts only the card charge |
| Arithmetic | Reaches $45.90 under these assumptions |
| Clarity | Separates the setup fee from merchandise |
| Correction | Revises the affected step when an input changes |
| Uncertainty | Asks or labels an assumption when information is missing |
Change one condition, not the entire question
Tell the assistant that the setup fee is $8 instead. The revised total should be $47.90. If it also changes the discount, quantity or unit price, record that as an unwanted revision. A correct final number accompanied by the wrong method still deserves scrutiny.
For a second check, remove the discount-scope instruction. Does the assistant ask what is discounted, or silently choose? Both behaviors can produce a plausible-looking total, but only an explicit assumption makes the result auditable. These checks assess your workflow; they do not establish population-wide model performance.
Record the active service context
OpenAI’s Free Tier FAQ describes separate limits for several tools. Record the model or mode shown in your actual session and whether a calculation tool was used. For DeepSeek, distinguish its own application from a third-party service using its models. The latter can have another operator, another configuration and different policies.
Do not compare one assistant’s tool-assisted calculation with another’s text-only reply and call the result a pure model comparison. Either allow the tools you intend to use in practice and label that choice, or keep the test conditions alike.
Pick the workflow you can inspect
Choose the assistant that keeps the inputs visible, handles your correction cleanly and lets you reproduce the answer. Use fictional data for the trial; real invoices and private financial details are unnecessary. A calculator or spreadsheet remains the independent numeric check.
If your next task involves a document rather than arithmetic, our ChatGPT Free vs Claude guide addresses file workflows and account limits. Match the comparison to the job rather than carrying a winner from one task into every other task.
Sources and freshness
This is source-informed editorial analysis, not a hands-on benchmark. Proposed tests are evaluation suggestions, not reported results. Features, prices, limits, and policies can change; verify current official terms before acting.
Reviewed Oct 8, 2026 · Independent publication.