Every tool you need,
one fast hub.

30 free calculators and utilities for students, small businesses and professionals. No sign-up, no uploads — everything runs privately in your browser.

🏠 Mortgage 🧾 Invoices 🎓 GPA 📱 QR Codes 📄 Merge PDFs 💱 Currency

Finance & Loans

Mortgages, loans, interest and investment returns.

Mortgage CalculatorMonthly payment, total interest and a full amortization schedule. Loan CalculatorPayments and total interest for personal, student or business loans. Car Loan CalculatorAuto payments with trade-in, down payment and sales tax. Compound InterestWatch savings grow with contributions and compounding. Credit Card PayoffHow long to pay off your balance — and what it really costs. ROI CalculatorTotal and annualized return for any investment or project. Savings GoalMonthly amount needed to reach any savings target. Percentage CalculatorPercent of, percent change, and "X is what % of Y". Currency Converter160+ currencies with daily-updated exchange rates.

Small Business

Invoices, margins, taxes and marketing utilities.

Invoice GeneratorProfessional invoices with tax and line items — print or save as PDF. Profit MarginMargin, markup, and the price that hits your target. Break-Even PointUnits and revenue needed to cover your costs. Sales Tax CalculatorAdd tax to a price — or back it out of a total. Salary ConverterHourly ↔ annual, plus weekly, bi-weekly and monthly pay. Discount CalculatorSale price after % off — including stacked discounts and tax. QR Code GeneratorQR codes for links, Wi-Fi and more — free PNG download. SEO Meta GeneratorTitle, description & Open Graph tags with length checks.

Students & Study

Grades, GPA, writing and study tools.

GPA CalculatorSemester and cumulative GPA, weighted by credits. Final Grade Calculator"What do I need on the final?" — answered precisely. Word CounterWords, characters, sentences and reading time as you type. Unit ConverterMetric ↔ imperial: length, weight, temperature and more. Study TimerPomodoro focus sessions with breaks and session tracking. Age CalculatorExact age, days lived, and next-birthday countdown.

Everyday & Files

Health, dates, text, images and PDFs.

PDF MergerCombine PDFs privately in your browser — no uploads. Image ConverterPNG ↔ JPG ↔ WebP with resize — no uploads. Password GeneratorCryptographically strong passwords, generated locally. Date CalculatorDays between dates, and date plus/minus any number of days. BMI CalculatorBody Mass Index with healthy-range context. Tip CalculatorTip, total, and per-person split in two taps. Case ConverterUPPER, lower, Title, Sentence, camel, snake & kebab case.

Why people use 4C Tool Hub

⚡ Instant & free

Every tool loads in under a second and works on any device. No accounts, no paywalls, no "premium" upsells — just answers.

🔒 Private by design

Calculations, files and text are processed entirely on your device. Your PDFs, images and numbers are never uploaded to a server.

🎯 Built for real tasks

Tools are organized around what you're actually doing — financing a home, running a shop, passing a class, or getting through the day.

📚 Learn as you go

Each calculator explains the formula behind it in plain English, so you understand the result instead of just copying it.