PercentMaster is a free, no-signup web app with 50+ calculators and utilities that run client-side.

Why I Built It

The catalyst was simple frustration. I'd reach for a calculator tool, and the experience would be one of:

• 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?

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.
• 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.
• 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.