I built PercentMaster out of frustration with calculator sites that seem stuck in 2025 aesthetics, demand your email address to calculate a tip, or force you through three ad pages before giving you your result.
The simple tool I first created for managing my finances has evolved into an integral part of my daily routine, and I now want to introduce it to anyone who values great user experience design, privacy, and practical problem-solving without any BS.
PercentMaster is a completely free, no-registration-needed web application packed with more than 50 calculators and utilities that process on the client side, load instantly, and describe their purpose clearly.
Why I Built It
What sparked it was pure frustration. It was the feeling of opening up a calculator tool and being greeted with:
- Bloated UI. Ads, pop-ups, and dark patterns everywhere.
- Friction to use. Sign up, verify email, accept cookies, then calculate.
- Privacy concerns. No visibility into whether your inputs were logged or sent somewhere.
- Vague or missing explanations. You get a number back. Cool. But what does it mean? When should you actually use this?
I wanted to build the opposite: something fast, transparent, and respectful of your time and data.
What's Inside
Finance & Math
- Percentage, discount, tip, and comparison calculators. The bread and butter.
- Loan & mortgage calculators with amortization clarity.
- Compound & simple interest. See how time and rates compound.
- Income tax, sales tax, and salary estimators. Quick snapshots for your location/scenario.
- Retirement & investment calculators. Rough projections to think about the long game.
Health & Education
- BMI, calorie needs, and macro tracking tools.
- GPA calculator. For students, parents, counselors.
- Age calculator. Because you might want to know how many days old you are.
Developer & Utility Tools (The Fun Stuff)
- Color converter. Hex, RGB, HSL, named colors—fast switching.
- Password generator. Configurable length and character sets; no server involved.
- Unit converter. Length, weight, volume, temperature.
- Currency & crypto converter. Real-time rates (fetched client-side only).
- Date calculator. Days between dates, add/subtract intervals.
- QR code generator. Text to scannable code instantly.
- Base64 encoder/decoder, JSON formatter/minifier, UUID v4 generator, Lorem ipsum generator. All the little things you Google for.
- Image compressor. JPEG and WebP, runs entirely in your browser. No uploads to a server.
The utilities lean into privacy: if a tool doesn't need the internet, it doesn't touch it.
Tech Notes
Stack: React + TypeScript, built with Vite, styled with Tailwind CSS and accessible Radix UI primitives.
What mattered: Speed (everything loads in one bundle ~150KB gzipped), clarity (every calculator has a readable explanation or guide), and privacy (utilities that don't need a server run locally—no telemetry, no logs).
The Honest Bit
PercentMaster is not a substitute for professional advice. For tax liability, medical decisions, or legal questions, consult a qualified professional. This is a thinking tool, not a decision-maker.
How to Use It
Visit percentmaster, pick a calculator, and go. No account. No email. No "free trial" leading to a paywall.
The information for the blog can be used to figure out the exact formula used in the calculation of the calculators.
Try starting with:
- The discount calculator if you want to feel good about your next purchase.
- The compound interest calculator if you want a small dose of motivation to save.
- The password generator if you've ever had to invent one by hand (we've all suffered).
What's Next
I'm always adding more tools based on what people ask for. If there's a calculator or utility you wish existed, let me know in the comments or reach out.
Thanks for stopping by. Hope it saves you some time.
Top comments (0)