You can build a working sales commission calculator for real estate agents with AI in a single afternoon, with no developer and no code you have to understand. You describe the tool in plain English to ChatGPT or Claude — sale price, fee percentage, agent and agency splits, GST — and it returns a single-page calculator you can use in the browser straight away. If the first version gets a number wrong, you tell it what you expected and it fixes it. That back-and-forth is the whole skill.
This guide is for an agent, sales manager or office administrator in an Australian agency who is tired of working out commission on the back of an envelope and wants a reliable tool they built themselves. No technical background needed. We will keep it a self-contained calculator — numbers in, numbers out — with no client data stored anywhere.
What you're actually building
A commission calculator real estate agents actually use does four things. It takes a sale price, applies the agency's fee (a percentage or a flat amount), calculates GST, and then splits the net commission between the agency and the salesperson. Some agencies add tiers, referral fees or a franchise cut. The beauty of building it yourself is that it matches your numbers, not a generic template's.
The output is a single HTML file — one page that runs in any browser. There is no database, no login and no server. That makes it the safest possible first build: nothing is stored, so there is no client data to protect. If you are new to the idea of describing software instead of coding it, our plain-English guide to vibe coding explains the mindset before you start.
Which AI tool to use, and where to click
You have two strong free options, and either works well.
- Claude (Artifacts). Go to claude.ai, sign in, and type your request in the chat. When Claude builds a tool, it renders a live preview in a panel on the right called an Artifact — you can click the buttons and test it immediately. The free tier is enough for this build.
- ChatGPT (Canvas). Go to chatgpt.com, sign in, and ask it to build the calculator. Canvas opens a side editor where the tool takes shape. The free tier works; a paid plan gives you more capacity if you iterate a lot in one sitting.
For a single-page calculator, Claude's Artifacts tends to feel slightly more immediate because the preview is interactive without extra steps. If you want a fuller comparison, we weigh them up in ChatGPT vs Claude vs Gemini for building small business tools. Pick one and stick with it for the whole build — swapping mid-way just confuses things.
The first prompt to type
Be specific about the inputs, the maths and the look. Vague prompts get vague tools. Paste something like this:
Build a single-page commission calculator for an Australian real estate agency. Inputs: sale price (dollars), commission rate (percentage), and a toggle to show the commission amount including or excluding GST. Calculate the gross commission as sale price multiplied by the rate. GST is 10%. Show the commission excluding GST, the GST amount, and the total including GST, each on its own line. Format all dollar figures with a dollar sign, commas for thousands, and two decimal places. Make it clean and simple, with large readable numbers. No login, no data saved.
Within a few seconds you will have a working calculator in the preview panel. Type a sale price and a rate and check it against a figure you already know is right. This first test is the most important thing you will do — never trust a calculator you have not checked by hand.
How do you handle GST on a commission calculator?
This is where agencies get it wrong, so handle it deliberately. In Australia, a GST-registered agency charges GST on its commission. The common confusion is whether a quoted commission rate is GST-inclusive or GST-exclusive — and the answer varies by agency and by how the agreement is worded.
Tell the AI exactly which convention you use. If your rate is quoted exclusive of GST (the usual case), the first prompt above is correct: gross commission, then add 10%. If you quote an inclusive rate, say so:
Change it so the commission rate is treated as GST-inclusive. Work backwards: the total including GST is sale price multiplied by the rate, the GST component is the total divided by 11, and the commission excluding GST is the total minus the GST. Label each line clearly so there is no doubt which figure includes GST.
That "divide by 11" is the standard way to extract GST from a GST-inclusive amount, and the AI will apply it correctly once you name it. Check both the inclusive and exclusive paths against a known figure before you rely on either.
Reacting when the first result is wrong
It often is, slightly — and fixing it is the actual skill, not a failure. You do not edit code. You describe the problem in plain English and let the AI correct it. Here are the reactions that come up most:
- Rounding looks off. "The GST amount is showing too many decimal places. Round every dollar figure to two decimal places and make sure the three figures add up exactly."
- A big number is hard to read. "Add comma separators so 1250000 shows as $1,250,000.00."
- It accepts junk input. "If the sale price or rate is blank or not a number, show a short message instead of a result, and don't display NaN."
- You want a worked example on screen. "Under the result, show the calculation in words, like: $850,000 × 2.2% = $18,700 commission, plus $1,870 GST, total $20,570."
Make one change per message. If you ask for five things at once and one breaks, you will not know which. Change, test, change, test.
Adding agent and agency splits
Once the GST maths is solid, add the split. This is what turns a fee calculator tool into something a salesperson actually wants:
Add a commission split. After calculating the commission excluding GST, add a field for the salesperson's percentage share. Show the salesperson's cut and the agency's cut separately, both excluding GST. Keep the GST line as the agency's responsibility and show it clearly as a separate figure.
If your agency runs tiers — say a higher split once a salesperson passes a sales target — describe the tiers in words and let the AI build the logic. If you have a franchise or referral fee that comes off the top first, say so and specify the order the deductions happen in. Order matters: taking a referral fee before versus after GST changes the numbers.
For agencies that want several of these small tools, it is worth reading our walkthrough on building a fee estimate calculator for your website with AI, which covers putting a calculator on a live page rather than keeping it internal.
Where it lives, who owns it, and keeping it out of shadow IT
A single HTML file is portable, which is both its strength and its risk. Ask the AI: "Give me the complete tool as one HTML file I can download and open in a browser." Save that file somewhere the agency controls — a shared drive folder, not a personal laptop desktop. That way it survives someone leaving.
Three ownership points matter:
- Maintenance. When your rates or splits change, you do not re-prompt from scratch — open the file's folder, start a new chat, paste the file in and describe the change. Keep the original prompt in a text file next to it so anyone can rebuild it.
- The AI product changes. Your downloaded HTML file keeps working regardless of what Claude or ChatGPT does next, because the logic lives in the file, not in the chat. That is exactly why a self-contained file is safer than a tool tied to a live AI account.
- Your firm's AI policy. A homemade calculator is still a tool the business relies on. Log it on your AI tool register so it is not invisible "shadow IT". Our note on vibe coding risks for professional services firms covers how to keep these builds governed without killing the useful ones.
What this calculator must not be used for
Keep it in its lane. This tool is a quick internal estimator, and that is all it should be.
- Do not put client or vendor personal details into it. There is no reason to — it only needs numbers. Keeping it free of personal information is what makes it a safe build. The OAIC's general guidance is clear that the Privacy Act applies the moment personal information goes into an AI system, and that publicly available chatbots should not be given personal information. For the full picture, see our explainer on AI and client data under the Australian Privacy Act.
- Do not treat the output as the agency agreement. The commission the vendor is legally charged is whatever the signed agency agreement says, calculated by your trust accounting system. This tool estimates; it does not replace the authority.
- Do not send it to a vendor without review. If you ever want a client-facing version on your website, have a person check every figure and the GST wording first, and consider whether a developer should harden it.
When the maths stops being simple — tiered trust disbursements, deposit handling, multiple agents on one sale with different agreements — stop and hand it to a developer or your trust accounting software. A one-page calculator is the right tool for a quick estimate, not for the money that actually moves.
If this build goes well and you want more quick wins like it, our free guide, 10 AI Workflows to Save 10+ Hours a Week, walks through the kinds of small, safe automations an agency can put in place without hiring anyone — and how to decide which ones are worth your afternoon.
Common questions
Do I need to know how to code to build a commission calculator with AI?
No. You describe what you want in plain English to ChatGPT or Claude and it writes the tool for you. When something is wrong, you explain the problem in words rather than editing code. The only skill you need is checking the result against a figure you already know is correct, so you can trust the numbers it produces.
How should the calculator handle GST on commission?
Decide first whether your commission rate is quoted including or excluding GST, because the maths differs. For a GST-exclusive rate, calculate the commission then add 10%. For a GST-inclusive rate, divide the total by 11 to find the GST component. Tell the AI which convention you use and label each figure clearly, then test both against a known amount.
Is it safe to build this tool with a free ChatGPT or Claude account?
Yes, provided you only ever enter numbers. This calculator needs sale prices, rates and percentages — no names or client details — so there is no personal information at risk. The OAIC's general guidance says the Privacy Act applies once personal information enters an AI system, so keeping the tool to figures only is what makes a free account appropriate here.
Where should the finished calculator live so it doesn't get lost?
Download it as a single HTML file and save it in a shared agency folder, not on a personal device. Keep the original prompt in a text file beside it so anyone can rebuild or update it later. Record the tool on your firm's AI register so it is governed rather than becoming untracked shadow IT.
When should I stop and hand this to a developer instead?
Stop when the maths stops being simple. Tiered trust disbursements, deposit handling, multiple agents on one sale with different agreements, or anything client-facing on your website all warrant a developer and proper review. A one-page calculator is ideal for a fast internal estimate, but it should never replace your trust accounting system or the signed agency agreement.
Want these ideas working in your firm? We build controlled AI workflows for Australian professional services firms — starting with a free automation audit.