Turning Your Workshop Math Into a Tool You Can Send as a URL

The formula for costing a 3D print is already on your machine. Material, electricity, machine depreciation, a coefficient to divide back out by success rate. Plenty of people have it in a spreadsheet and use it every week.

The trouble starts when you try to give it to somebody. Send the file and whoever opens it breaks a formula. You also have to explain how to use it. So you end up saying “tell me and I will run it for you”, and the tool never leaves your hands.

ChatGPT Sites takes on that last step. You describe what you want, it builds a web page or small web app, and it hosts and shares it. From the maker’s side the shape of the problem is neat: you already have the formula; what you are missing is input fields and something you can send.

Our position first. We have not used this feature and have not verified its behaviour. What follows is a reading of the official documentation and the terms of service. Checked on 6 September 2026; the Sites terms page showed a last-updated date of 23 July 2026. And the conclusion, stated up front: there is more to read before you hand it out than there is to work out about building it.

You have the formula. What is missing is the container

It helps to start from the material. Of the calculations we have covered here, these are the ones worth turning into tools.

In each case the formula is already verified and already published here. The costing approach is in recalculating 3D print cost at Japanese electricity rates, and estimating before a long run is in settings for batch printing.

What is different from sending a spreadsheet

The significant part is that hosting is included. That is where the whole difference from passing files around collects: the recipient only opens a URL, needs no particular software, and cannot break a formula.

Publishing is a two-stage process. You save a version you can review first, and deploy after you have looked at it. Every deployment URL is a production URL, so the review step is the safeguard — nothing goes out in a single click by accident.

By default only you and your administrator can see it

This is easy to get wrong, so it goes early. A newly created Site is visible to its owner and workspace administrators only. Making one does not put it in front of the world.

The sharing options depend on your account, and include specific members or groups in the workspace, invited external viewers, the whole workspace, and full public access. Of these, public access has to be enabled by an administrator on business plans.

So widening the audience is always an explicit act. You cannot build and immediately distribute — but by the same token, accidental exposure is unlikely.

Decide who it is for before you build it

Having several sharing options means you have to choose how far to open it, and that choice is better made before building than after.

The reason is that the audience changes the tool. For yourself, you need no explanation of the inputs and no worry about strange values. For a handful of colleagues, units and input order need to be consistent. For the general public, assumptions have to be on the screen or they will be misread.

In costing terms, the electricity rate and the success-rate estimate differ by workshop. Embedding your own values is fine for your own use, but if you are handing it out, the screen has to say where those numbers came from. An unlabelled number gets taken for the reader’s own.

Settling the audience early also tells you which terms below apply to you, because several clauses simply do not engage unless you go public.

The difference from Custom GPTs is where the thing lives

Custom GPTs cover similar ground and have for a while. In one line: a Custom GPT lives inside ChatGPT; a Site lives at a URL. The recipient of the first needs an account and has to converse with it; the recipient of the second opens a link and fills in fields.

That makes the choice mostly about the recipient, not the builder. A fixed calculation with known inputs suits a Site. Something used conversationally suits a Custom GPT — the build process is covered in building a 3D printing assistant with Custom GPTs.

Storage limits and the default domain

The technical conditions, per the documentation: 10 GB of data storage, with no fixed cap stated on file storage. A small calculator will not come near either.

On addresses, the terms note that a provider-owned subdomain ending in chatgpt.site may be assigned. Acquiring an unreasonable number of subdomains, or attempting to resell them, is prohibited. Connecting a domain you own is possible in some cases, via DNS changes, though the documentation words this conditionally — “where available”. Custom domains are noted as unavailable for Enterprise workspaces at launch.

From here on it is a question about the terms

So it can be built. The question is whether you should hand out what you built, and that is no longer a question about the feature. Distribution carries obligations that do not appear in a feature description. What follows is what we could establish from the Sites-specific terms of service.

What you make is yours — and you grant an irrevocable licence

On ownership, the terms are clear: content you put on a Site is your content, and you retain any ownership rights in it. You do not need to worry about the tool becoming somebody else’s.

At the same time you grant the provider a licence. It is scoped — limited to what is needed to provide and operate the Site according to the sharing and publication settings you chose — but its character is non-exclusive, worldwide, irrevocable and royalty-free.

“Irrevocable” is the word not to skim. Hosting obviously requires permission to store, copy and display. Still, it is worth knowing that the permission, once given, is not structured to be withdrawn.

A provider credit may appear in the footer

One more clause touches how the thing looks. The terms state that a credit or link indicating the Site is powered by ChatGPT may be displayed in the footer or toolbar.

A tool you hand out under your own name carries another company’s mark. Whether that is acceptable depends on the use. For an internal calculator, nobody will mind. For something embedded in material you give a client, it is a decision.

Relatedly, if you set a Site to fully public you grant the provider a limited licence to use names and logos on the Site for promotional and referential purposes. Displaying anything that would lead a third party to believe the provider created or endorsed your Site is prohibited.

You may sell. All the responsibility is yours

Whether commercial use is allowed decides whether this belongs in a business at all, and the terms address it. You may use a third-party payment processor to sell goods or services and collect payments. Putting a charge on what you built is not itself prohibited.

The conditions are extensive. You are solely responsible for fulfilment, delivery, refunds, customer support, billing and warranties on anything sold, and likewise for calculating, collecting and remitting tax. The agreement with the payment processor is yours alone, and the provider takes no responsibility for payments passing through it. Implementing, configuring and maintaining that integration is also on you.

Separately, initiating or executing financial transactions without going through a third-party payment processor is prohibited. Building only the payment part yourself is not an available option.

The moment you collect input, you become a data controller

This is probably the heaviest clause in the document. If your published Site collects personal data, you become the controller of that data. The examples given are allowing users to post or upload content, enabling login or authentication, and using cookies or similar technologies.

What being a controller requires is spelled out: providing the necessary transparency and disclosures about use, providing appropriate means to obtain and withdraw consent for collection and use, and obtaining any other necessary contracts or consents. Where the law requires it, you must produce a compliant privacy policy and post it on the Site.

Bring that back to our own subject. A costing tool that does not store what is typed into it is not collecting personal data. But the moment you think “it would be handy to keep a history” and add storage, the position can change. Adding one feature changes your legal standing.

Data you must not handle

The documentation also names categories that Sites must not process, including protected health information and payment card data (unless solely through a third-party payment processor). Sites must not target children under 13, distribute malware, enable phishing, impersonate people or organisations, or otherwise violate the usage policies.

For a workshop calculator none of this is close to the line. It matters as soon as you consider taking customer details through the same tool.

It can be taken down at any time

One more clause is unavoidable when deciding whether this belongs in a working process. The terms reserve the right to delete, remove, unpublish or disable a Site at any time. Policy violation and risk of harm are given as examples, but the clause itself does not limit the reasons.

On top of that, Sites is a beta service, stated as such in the terms and matching the “public beta” language in the documentation. There are also plan-specific usage limits during the beta; reaching one may prevent you creating a new Site, adding storage, or keeping a high-usage Site publicly available.

The conclusion from those two points is straightforward. Do not put anything here that your work stops without. Separate tools that are convenient to hand out from tools you cannot operate without. The first fits well. The second is premature.

What suits it, and what does not

Suits it: tools that store no input and simply calculate and display on the spot. Unit cost. An estimate from print time. Clearance from fit dimensions. How many pieces remain in a spool. Each is a closed calculation that finishes on screen.

Does not suit it: tools that keep records, tools edited by several people, tools that receive customer information. All are technically buildable, and all put controller responsibility on you the moment they exist. Measurement logging is the interesting borderline — the measuring method itself is covered in measuring drawers and equipment for a good fit, but whether to put those records in somebody else’s hands is a separate decision.

And anything you cannot afford to lose does not suit it. The deletion clause and the beta status are the reasons, and they are reason enough.

What we have not verified

• We have not used the feature. Nothing here reports how easy it is to build with or how it behaves.
• Availability from Japan and behaviour in Japanese are unverified. A Japanese version of the terms exists, which is a separate matter from where the feature is offered. At launch it was noted as unavailable in the EEA, Switzerland and the UK.
• Concrete per-plan limits are not published. The documentation says limits exist and that you are notified as you approach them, without giving numbers, so we do not guess at them either.
• How the takedown clause is applied in practice is not something the terms can tell you.

In short

Building is the easy half. What you already have — a verified formula — is the part that is hard to come by, and Sites supplies the missing container: input fields, hosting, and a URL you can send.

The work is on the other side of that. Decide the audience before you build, because it changes the tool and it decides which clauses apply to you. Keep it to closed calculations that store nothing, because storing input can make you a data controller. Do not put anything load-bearing there, because the terms allow removal at any time and the service is in beta.

Read that way, this is a good fit for a specific, useful thing: taking a calculation you have already checked and making it something a person can open and use without you. That is a real gain, and it is worth being clear that it is the whole of the gain.

Sources

• OpenAI Help Center, “Creating and managing ChatGPT Sites”
• OpenAI, “ChatGPT Sites Terms”

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