Guides, Tutorials & How-To Articles

Learn how to use our free online tools for finance, math, coding, health, and productivity. Every guide is original and packed with worked examples so you can turn a simple utility into a real workflow.

Popular topics

  • How loan EMI and compound interest are calculated
  • Password strength & entropy explained
  • Base64, JSON & URL encoding for developers
  • Time-zone scheduling and the Pomodoro method

All articles

How Loan EMI Is Calculated
Finance

How Loan EMI Is Calculated (With Formula)

The EMI formula, a full worked example, and how tenure and interest rate change your monthly payment.

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Compound Interest Explained
Finance

Compound Interest Explained With Examples

How compounding grows money over time, with formulas, comparison tables, and the Rule of 72.

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Calculate Percentages
Math

How to Calculate Percentages: Every Common Case

Percent of a number, increases and decreases, reverse percentages, and percentage points made clear.

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Unit Conversion Guide
Math

Metric vs Imperial: A Complete Unit Conversion Guide

Convert length, weight, volume, and temperature with confidence — plus the context behind each unit.

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Password Strength & Entropy
Security

Password Strength & Entropy Explained

What makes a password strong, how entropy is measured, and how long cracking one really takes.

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URL Encoder & Decoder
Development

URL Encoder & Decoder Explained

Why URLs need encoding, how special characters convert, and where this tool saves developers time.

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JSON Formatter Tutorial
Development

JSON Formatter Tutorial for API Work

Clean up messy API data, format JSON for readability, and catch syntax errors before you send requests.

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Base64 for Developers
Coding

Base64 for Developers: Data URIs, APIs & Email

Practical Base64 use in data URIs, JSON payloads, and email attachments — with the trade-offs.

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BMI Calculator Guide
Health

BMI Calculator Guide: What the Numbers Mean

Understand BMI ranges, what they tell you, and the real limitations of a single number.

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The Math Behind Age
Lifestyle

The Math Behind Age Calculation: Leap Years & Edge Cases

Leap years, differing month lengths, and the edge cases that trip up manual date math.

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Time Zone Conversion
Productivity

Time Zone Conversion for Remote Teams

Schedule across time zones, handle daylight saving, and avoid painful meeting mix-ups.

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The Pomodoro Technique
Productivity

The Pomodoro Technique: A Practical Guide

Use focused 25-minute sprints to beat procrastination and get meaningful work done.

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Ideal Word Counts
Writing

Ideal Word Counts: SEO, Essays, Emails & Social

Target word counts that actually work across blog posts, essays, emails, and social platforms.

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Tip Calculator Guide
Finance

Tip Calculator Guide: How to Calculate & Split Tips

The simple tip formula, standard tipping percentages, and how to split a bill fairly with an example.

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Credit Card Payoff
Finance

Credit Card Payoff Calculator: Get Debt-Free Faster

How interest works, the minimum-payment trap, and avalanche vs snowball strategies to clear debt.

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Investment Return
Finance

Investment Return Calculator: ROI, CAGR & Compounding

ROI vs CAGR explained, with formulas and a worked example so you can compare investments fairly.

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Temperature Converter
Math

Temperature Converter: Celsius, Fahrenheit & Kelvin

The conversion formulas and worked examples for switching between the three temperature scales.

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Roman Numerals
Math

Roman Numerals Converter: Rules, Chart & Examples

How Roman numerals work, the subtractive rule, a full chart, and examples up to the thousands.

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Calorie Burn Calculator
Health

Calorie Burn Calculator: How Many Calories Do You Burn?

How the MET method estimates calories burned, common activity values, and a worked example.

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Ideal Weight Calculator
Health

Ideal Weight Calculator: Formulas and What They Mean

The Devine formula and its variations, plus how a healthy BMI range compares as an alternative.

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Water Intake Calculator
Health

Water Intake Calculator: How Much Water Should You Drink?

Estimate daily water needs from body weight, and the truth about the "8 glasses a day" rule.

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Macro Calculator Guide
Health

Macro Calculator Guide: Protein, Carbs and Fat Explained

How macros convert to calories and how a calculator splits a daily target, with an example.

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UUID Generator Guide
Development

UUID Generator Guide: What UUIDs Are and When to Use Them

The 128-bit UUID format, version 1 vs version 4, collision odds, and practical uses.

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Regex Tester Guide
Development

Regex Tester Guide: Test and Debug Regular Expressions

Common regex tokens and flags explained, with a worked email pattern and debugging tips.

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Color Converter Guide
Development

Color Converter Guide: HEX, RGB, HSL and When to Use Each

HEX, RGB, and HSL explained with a worked conversion and guidance on when to use each format.

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CSS Gradient Guide
Development

CSS Gradient Generator Guide: Linear, Radial & Conic

How CSS gradients work, the three types, and how to build smooth backgrounds with confidence.

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Case Converter Guide
Writing

Case Converter Guide: UPPERCASE, lowercase, Title Case & More

Every text case explained, from Title Case to camelCase and snake_case, with rules and examples.

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Lorem Ipsum Guide
Design

Lorem Ipsum Guide: What Placeholder Text Is and How to Use It

The origin of Lorem Ipsum, why it is used in design, and when to replace it with real copy.

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