Blog & Guides
In-depth explainers on developer tools, calculators, and online utilities. Learn the math and code behind 367 free tools.
8 articles in calculator
How to Calculate BMI: Formula, Ranges, and Limitations
The complete guide to Body Mass Index โ the formula, WHO ranges, what BMI actually tells you, and its well-known limitations.
How Mortgage Payments Are Calculated: The Math Behind Your Monthly Bill
Understand the amortization formula, how your payment splits between principal and interest, and how extra payments can save you thousands.
Compound Interest Explained: The Most Powerful Force in Finance
How compound interest works, the formula, compounding frequencies, the Rule of 72, and why it matters for both savings and debt.
Percentage Calculations: The Complete Guide with Formulas
Master every type of percentage calculation โ basic percentages, percentage change, working backwards, and real-world examples for discounts, tax, and grades.
How Currency Exchange Rates Work: A Plain-English Guide
Understand spot rates, bid/ask spreads, what moves exchange rates, and how to get the best rate when converting currency for travel or business.
Understanding TDEE and Macros: How to Calculate Your Daily Calorie Needs
A complete guide to calculating your TDEE (Total Daily Energy Expenditure) and macros โ the Mifflin-St Jeor formula, activity multipliers, and practical nutrition planning.
How EMI Is Calculated: Understanding Your Loan Repayment
A complete guide to EMI calculation โ the formula, flat rate vs reducing balance, how tenure affects total interest, and prepayment benefits.
How to Calculate ROI: Formulas, Examples, and Common Mistakes
Master ROI calculation โ the basic formula, annualized ROI, what counts as costs and gains, and how ROI compares to IRR and NPV.