How to Calculate Percentages in Your Head and on Paper
Master mental math percentage formulas for tips, shopping discounts, sales tax, and performance metrics.
Table of Contents
The Core Percentage Formula
Percentage simply means "per hundred". The universal formula is: (Part / Whole) × 100 = Percentage %.
Conversely, to find X% of Y: Multiply Y by X, then divide by 100.
Mental Math Tricks: The 10% and 1% Rules
To find 10% of any number, move the decimal point one place to the left ($64.00 becomes $6.40).
To find 1% of any number, move the decimal point two places to the left ($64.00 becomes $0.64).
To calculate a 15% tip on $60: 10% is $6. Half of that (5%) is $3. Sum them: $6 + $3 = $9 tip!
Put this guide into practice
Percentage Calculator
Calculate percentage of a number, percentage change, and relative percentage values.
Percentage Increase Calculator
Calculate the percentage growth from an original value to a higher new value.
Discount Calculator
Calculate sale prices, total dollar savings, and additional stacked discounts.