Body Mass Index Calculator
Estimate BMI from height and weight in metric or imperial units.
What it adds
Build a simple BMI estimator with metric and imperial inputs and a clearly labeled educational result.
What your builder is told to do
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What your builder is told to do
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1
Inspect any unit preferences, category ranges, or copy guidance in the source files.
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2
Create height and weight inputs with a metric / imperial toggle.
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Calculate BMI and show the standard category band, labeled as an estimate for general information only.
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Add a reset control and a next-step CTA appropriate to the offer.
Edge cases it handles
5
Edge cases it handles
5- Keep the tool focused on one primary job. If the source asks for a suite, build the first usable tool and list the obvious follow-ups.
- Do not invent testimonials, guarantees, legal disclaimers, revenue numbers, scarcity, or unverifiable claims.
- If formulas, scoring weights, or recommendation rules are missing, create editable placeholders and call out the assumptions.
- If payment, email, analytics, CRM, or storage integrations are missing, build clear seams and document the variables or endpoints still needed.
- Match the existing app or page design system unless the user explicitly asks for a standalone visual direction.
Definition of done
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Definition of done
5- The tool is buildable as a standalone page, lightweight SPA, embeddable widget, or cleanly integrated app screen.
- The primary input, primary output, and primary action are obvious without extra instructions.
- The implementation includes empty, loading, error, and completed states.
- Mobile, tablet, and desktop layouts are accounted for.
- The agent reports the source files used, assumptions made, and any formulas or rules that still need owner review.
Related tool files
Savings Calculator
Savings Calculator
Show what a user saves in time, money, waste, or effort over time.
What it does
Build a savings calculator with adjustable assumptions and a concise comparison against the current state.
How it works
- 1 Identify the before-state cost and after-state improvement promised by the source files.
- 2 Create simple inputs for current spend, frequency, time period, and expected improvement.
- 3 Display savings by period plus the key assumption driving the result.
Copy the prompt
No account needed
Build this as a complete, standalone tool. Read the blueprint first and follow it exactly — make it responsive, handle empty and error states, and keep it production-ready:
https://buildthistool.com/x/savings-calculator
SaaS Pricing Calculator
SaaS Pricing Calculator
Let buyers model plan cost from seats, usage, billing cycle, and add-ons.
What it does
Build a SaaS pricing calculator that makes the right plan and estimated monthly or annual cost easy to compare.
How it works
- 1 Inspect pricing docs for plans, limits, included usage, add-ons, discounts, and billing terms.
- 2 Create inputs for seats, usage, billing cycle, add-ons, and required capabilities.
- 3 Show the recommended plan, price breakdown, savings, and edge cases such as overages.
Copy the prompt
No account needed
Build this as a complete, standalone tool. Read the blueprint first and follow it exactly — make it responsive, handle empty and error states, and keep it production-ready:
https://buildthistool.com/x/saas-pricing-calculator
Freelance Rate Calculator
Freelance Rate Calculator
Turn target income, billable hours, and expenses into an hourly and day rate.
What it does
Build a freelance rate calculator that converts income goals, overhead, and realistic billable capacity into a defensible rate.
How it works
- 1 Inspect any income targets, expense lists, tax assumptions, and billable-hour notes in the source files.
- 2 Create inputs for target take-home, business expenses, tax buffer, working weeks, and billable hours per week.
- 3 Calculate the required hourly, half-day, day, and project rates with each assumption shown and editable.
Copy the prompt
No account needed
Build this as a complete, standalone tool. Read the blueprint first and follow it exactly — make it responsive, handle empty and error states, and keep it production-ready:
https://buildthistool.com/x/freelance-rate-calculator
How it works
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1
Copy the link
Grab the Markdown blueprint URL for this tool type.
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2
Give it to your builder
Paste it into Claude Code, Cursor, Codex, or whatever AI builder is already working in your app.
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3
It maps, then builds
Your agent reads the blueprint first, then builds the tool into your app around the rules, audience, and stack.
Works with your stack
These blueprints are written to adapt. They tell the agent to detect your framework, match your existing design system, and use your source files instead of guessing the tool rules.
Need it tighter than that? Customize the tool file and tell it exactly which source docs and stack to use.