Guides & explainers
Original, practical articles that teach the math behind our free calculators. Written for students, shoppers, freelancers, and anyone who wants to understand percentages—not just get a number.
How to Calculate Percentages
Learn how to calculate percentages by hand and with free tools. Formulas for percent of a number, reverse percentages, increase, decrease, and real examples.
8 min read →
Percentage Increase vs Percentage Points
Clear explanation of percentage change versus percentage points, with examples for interest rates, polls, grades, and statistics.
6 min read →
How to Calculate a Tip
Learn how to calculate restaurant and delivery tips. Common tip percentages, split bills, pre-tax vs post-tax tipping, and free tip calculator.
5 min read →
How to Calculate Discounts
Step-by-step discount math: sale price, amount saved, stacked discounts, and coupons. Includes formulas and a free discount calculator.
6 min read →
Markup vs Margin Explained
Understand the difference between markup and profit margin. Formulas, examples, and when to use each — plus free markup/margin calculator.
7 min read →
Compound Interest Basics
Plain-language guide to compound interest: formula, compounding frequency, examples, and how it differs from simple interest. Free calculator included.
7 min read →
How to Calculate VAT
Learn how to add VAT to a net price or extract VAT from a gross total. Formulas, examples, and common mistakes for sales tax and VAT.
6 min read →
How Loan EMI Works
Plain explanation of equated monthly installments (EMI), amortization, interest vs principal, and what a fixed-rate loan calculator can and cannot tell you.
7 min read →
Mental Math for Percentages
Practical percentage shortcuts: finding 10%, 5%, 15%, 20%, and combining them for tips, discounts, and quick estimates without a calculator.
5 min read →
Common Percentage Mistakes
Avoid frequent percent errors: mixing up base values, confusing percentage points with percent change, stacking discounts incorrectly, and dividing by zero.
6 min read →
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