Course: Building AI Apps | Pathway: Builder | Tier: Free | Level: Beginner Estimated Reading Time: 9 minutes
A micro app is a small, focused tool that does one thing. Not ten things. Not five. One.
That constraint is actually what makes micro apps so effective. Because they do one thing, they're fast to build, easy to understand, and simple to share. You can go from idea to live URL in an afternoon.
Examples of micro apps:
These aren't complex pieces of software. They're small, useful tools that solve a specific problem for a specific audience.
Micro apps are valuable for three reasons:
1. They're the fastest way to learn. Building a micro app teaches you the entire process — describing what you want, working with AI, testing, refining, and deploying — without the complexity of a larger project. It's like learning to cook by making toast before attempting a roast dinner.
2. They're genuinely useful. A well-made micro app that solves a real problem will get used. People bookmark them, share them, come back to them. A GST calculator that works well is more valuable than a half-finished project management tool.
3. They build confidence. Every micro app you complete is proof that you can build things. That confidence compounds. After building three or four micro apps, you'll feel ready to tackle something bigger — because you've already done the hard part of learning the process.
Let's walk through building a micro app from start to finish. We'll build a meeting cost calculator — a tool that shows how much a meeting actually costs based on attendees and duration.
Write one sentence that describes what your micro app does.
Our example: "A calculator that shows the total cost of a meeting based on the number of attendees, their average hourly rate, and the meeting duration."
That's it. If you can't describe your micro app in one sentence, it might be too big. Break it down further.
Inputs (what the user provides):
Outputs (what the app shows):
Open Replit (or your preferred tool) and describe what you want:
Build a meeting cost calculator web app with these features:
Inputs:
- Number of attendees (slider or number input, range 2-20, default 5)
- Average hourly rate per person in NZD (number input, default $50)
- Meeting duration in minutes (slider or number input, range 15-120, default 60)
The calculator should update in real time as the user changes any input.
Display:
- Total meeting cost (prominently displayed, large font)
- Cost per minute
- A fun comparison like "That's equivalent to X flat whites at $6 each"
Design:
- Clean, minimal layout
- Centred on the page
- Professional colour scheme
- Works well on mobile
- Title: "Meeting Cost Calculator"
- Subtitle: "See what that meeting really costs"
The AI will generate a working app. Open it and check:
You'll almost certainly want to adjust things. Here are common refinements:
Each of these is a small, specific request. That's the key to effective refining — one change at a time, so you can see exactly what changed and whether it's right.
Once you're happy with it:
Send the link to a colleague. Post it on LinkedIn. Add it to your website. It's yours.
Here are a few more micro app ideas with example prompts you can adapt.
Build a simple quote calculator for a house painting business.
The user selects:
- Number of rooms (1-10)
- Room size (Small, Medium, Large)
- Paint quality (Standard, Premium)
Show an estimated price range based on:
- Small room: $300-400 standard, $400-550 premium
- Medium room: $450-600 standard, $600-800 premium
- Large room: $650-850 standard, $850-1100 premium
Display the total estimate as a range. Include a note that says
"This is an estimate only. Contact us for an exact quote."
Add a "Request a Quote" button that links to mailto:quotes@example.co.nz
Build a countdown timer web app.
The user enters:
- Event name
- Event date and time
The page shows a live countdown with days, hours, minutes, and seconds.
The design should be clean and large enough to display on a screen at an event.
When the countdown reaches zero, show a celebration message.
Include a "Share" button that copies the page URL.
Build a "Where should we go for lunch?" randomiser.
The user can:
- Add restaurant names to a list
- Remove restaurants from the list
- Click a big "Pick for us!" button
- The app randomly selects one with a fun spinning animation
- The list is saved in the browser so it persists
Start with these defaults: Thai Chef, Sushi Train, The Good Home,
Sal's Pizza, Subway, that Korean place on Cuba Street
Give users sensible defaults. Don't make people fill in every field before they see anything. Start with reasonable default values so the app is immediately useful.
Make it work on phones. Most people will access your app on their phone. Always test on a narrow screen. Ask the AI to "make sure it's mobile responsive" if it doesn't look right on small screens.
Keep the interface obvious. A micro app should be self-explanatory. If someone needs instructions to use your calculator, the design needs work. Labels should be clear, buttons should say what they do, and the result should be prominent.
Handle edge cases. What happens if someone enters zero for the hourly rate? Or 200 attendees? Test unusual inputs and make sure the app either handles them gracefully or prevents them.
Add a personal touch. A small detail like a fun comparison ("That's 42 flat whites") or a well-chosen subtitle makes the app feel considered rather than generic.
Once you've built your first micro app, the second one takes half the time. And the third takes half again. You start recognising patterns — how to describe inputs and outputs, how to phrase refinements, what to test for.
Some people build a collection of micro apps. A financial advisor might have a savings calculator, a mortgage comparison tool, and a retirement readiness quiz — each one a separate micro app, but together they form a useful toolkit for their clients.
A trades business might have a quote estimator, a job time tracker, and a materials calculator.
The point is: you don't need one big app. Sometimes a collection of small, focused tools is far more useful.
In the final lesson, we'll cover how to properly deploy and share your apps. We'll look at custom domains, Vercel hosting, and how to get your work in front of the people who need it.
Key Takeaways: