How to use Claude to build custom calculators
A former programmer used Claude via Windsurf to turn detailed calculator requirements into a live multilingual site with more than 60 calculators.
news.ycombinator.com
Original prompt
Shared by the source author. See source notes for context.
compound interest calculator with monthly/quarterly/yearly options, year-by-year breakdown table, recurring contribution support
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See placements →Evidence at a glance
Sourced account- Source poster / publisher
- ivcatcher
- Original account
- Read the source ↗
- Published
- Source link checked
- Reported result
- The author reports a live site with over 60 calculators after two weeks and roughly $100 in API costs.
- Human involvement
- The author supplied detailed behavior and UX expectations and contributed financial-math knowledge; a formal code-review process is not described.
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How the agent did it
- Describe compound-interest requirements including compounding options and recurring contributions.
- Have Claude implement the calculator with validation, components and tests.
- Expand the collection to financial calculators and other utilities.
After years away from programming, the author used Claude through Windsurf to build calculators they wanted to use themselves. Their starting point was dissatisfaction with existing compound-interest tools, particularly interfaces, compounding options and missing year-by-year breakdowns. They described the desired behavior directly, including monthly, quarterly and yearly compounding, recurring contributions and a breakdown table.
The author says Claude delivered the calculator with validation, interface components and tests. They then expanded the collection to mortgage calculations, loan amortization, savings goals and retirement projections, followed by tools such as a BMI calculator, timezone converter and regex tester. After two weeks, they reported more than 60 calculators and roughly $100 in API costs using the Opus 4.5 thinking model.
The live site used Next.js, React, TailwindCSS and shadcn/ui, with English, German, French and Japanese. According to the author, the AI selected most of that stack after being asked for something modern and clean. Who it's for: returning programmers who can specify desired behavior and contribute domain knowledge while using an agent for implementation.
Prompt
Original prompt
Source: Hacker News · ivcatcher
Frequently asked questions
What requirements started the calculator project?
The author requested a compound-interest calculator with monthly, quarterly and yearly options, a year-by-year breakdown table and recurring contribution support.
What did the author report building?
They reported more than 60 calculators in two weeks, including financial calculators and utilities, with roughly $100 in API costs. The site was live.
More details
Remaining steps
- Publish the multilingual calculator site at calquio.com.
About this account
Claude handled implementation and selected most of the stack in response to the author's requirements and design preferences.
Platform: Hacker News. Attribution: https://news.ycombinator.com/item?id=46673809. Prompt: Original (quoted from source). Sourced by the Agents In Use pipeline.
Credit: ivcatcher on Hacker News
Source published
Added to Agents In Use
Source checked
Tools and topics
Claude · Windsurf · Next.js · React · TailwindCSS · shadcn/ui
Calculators · Web development · Returning programmers
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.