Calculator Guides
In-depth guides on compound interest, mortgages, BMI, GPA, percentages, and retirement planning with links to free calculators.
How Compound Interest Works
Understand how money grows when interest earns interest — the math, examples, and why starting early matters.
6 min read · Updated July 13, 2026
Mortgage Explained
A clear guide to how mortgages work — payments, amortization, PMI, and what to budget beyond the monthly bill.
8 min read · Updated July 13, 2026
How BMI Is Calculated
Learn the BMI formula, category ranges, limitations, and when to use alternative health metrics.
5 min read · Updated July 13, 2026
How GPA Works
Grade point averages explained — calculation, credit weighting, scales, and conversion to percentage.
5 min read · Updated July 13, 2026
Percentage Formula Guide
Every percentage formula you need — percent-of, increase, decrease, change, and reverse calculations with examples.
4 min read · Updated July 13, 2026
Retirement Planning Basics
Core concepts for retirement savings — compound growth, contribution strategies, and how to project your nest egg.
7 min read · Updated July 13, 2026
How Mortgage EMI Is Calculated
The standard EMI formula for fixed-rate loans, a full numeric example, and how principal and interest split over the term.
9 min read · Updated July 13, 2026
BMI Categories Explained
WHO adult BMI ranges from underweight through obese classes, what each band means, and when BMI alone is not enough.
8 min read · Updated July 13, 2026
Percentage Increase and Decrease Guide
Formulas for percent change, increase, decrease, and the common mistake of using the wrong base value — with worked examples.
7 min read · Updated July 13, 2026
Compound vs Simple Interest
Side-by-side formulas, numeric comparisons, and when each type applies to savings, loans, and investments.
9 min read · Updated July 13, 2026
Calorie, BMR, and TDEE Basics
How basal metabolic rate and total daily energy expenditure differ, how to set a calorie deficit or surplus, and numeric examples.
8 min read · Updated July 13, 2026
Loan EMI Formula Explained
The standard equated monthly installment formula for home, auto, and personal loans — with worked examples and how principal and interest split over time.
8 min read · Updated July 13, 2026
Age and Date Difference Guide
How to calculate age from date of birth, count days between two dates, and estimate business days for deadlines and planning.
7 min read · Updated July 13, 2026
Payroll & Take-Home Pay Explained
How gross salary becomes net pay — federal and state withholding, FICA, deductions, and what employers pay on top.
7 min read · Updated July 13, 2026
Class Attendance Requirements Guide
How colleges calculate attendance percentage, common thresholds like 75%, and how many classes you can miss.
5 min read · Updated July 13, 2026
Margin vs Markup vs Profit Margin
The difference between margin, markup, and profit margin — formulas, examples, and when to use each.
6 min read · Updated July 13, 2026