Percentage Calculator

Calculate percentages instantly. Find what percent a number is of another, calculate percentage increase/decrease, sales tax, discounts, and tips with step-by-step arithmetic.

Percentage Formula Mode

Live calculation
Quick Sample Presets
%
25% of 200
50

Arithmetic Execution

Formula step
(
25100
) × 200 = 50.00

Understanding Percentages and Proportions

A percentage is a dimensionless mathematical ratio expressed as a fraction of 100. Derived from the Latin per centum("by a hundred"), percentages provide a standardized scale to evaluate financial growth, retail discounts, interest yields, scientific variance, and statistical changes.

1. Percentage of a Number (What is X% of Y?)
Result=
X100
× Y
2. Percentage Ratio (X is What % of Y?)
Percentage (%)=
X (Part)Y (Whole)
× 100
3. Percentage Change (Increase or Decrease)
Percentage Change (%)=
New Value - Old ValueOld Value
× 100
Step-by-Step Calculation Breakdown
Example 1: Finding 25% of 200
Result=
25100
× 200=0.25 × 200=50.00
Example 2: What % is 50 of 200?
Percentage=
50200
× 100=0.25 × 100=25.00%
Example 3: Percentage Growth from $100 to $125
Growth=
125 - 100100
× 100=
25100
× 100=+25.00%

Mental Math Percentage Shortcuts & Benchmark Guide

PercentageEquivalent FractionDecimal FormFast Mental Arithmetic Rule
10%1/100.10Move the decimal point 1 place to the left (e.g. 10% of 250 = 25).
5%1/200.05Find 10% and divide by 2 (e.g. 5% of 250 = 25 ÷ 2 = 12.5).
15% (Tip)3/200.15Find 10% and add half of that amount ($60 bill: $6 + $3 = $9 tip).
20% (Standard Tip)1/50.20Find 10% and double it ($80 bill: $8 × 2 = $16 tip).
25% (Quarter)1/40.25Divide by 4 (or divide by 2 twice: 25% of 240 = 120 → 60).
50% (Half)1/20.50Divide by 2 (e.g. 50% of 250 = 125).

Frequently Asked Questions

What does 'percent' mean literally?
The word 'percent' comes from the Latin 'per centum,' meaning 'by a hundred.' A percentage is simply a fraction with a denominator of 100. For instance, 25% represents 25 parts out of 100, or 25/100 = 0.25 in decimal notation.
How do I calculate a percentage increase or decrease?
Subtract the original baseline value from the new value, divide that difference by the original baseline value, and multiply by 100: ((New - Old) / Old) × 100. If positive, it is a percentage increase; if negative, it is a percentage decrease.
What is the difference between percentage and percentage points?
If a mortgage interest rate rises from 5% to 7%, that is a 2 percentage point increase (7 - 5 = 2 points), but a 40% relative increase ((7 - 5) / 5 × 100 = 40%). Percentage points measure absolute subtraction, while percent measures relative proportional change.
Why can't you simply add sequential percentages?
Percentages scale relative to their current base. A 10% discount followed by another 10% discount does not equal a 20% discount; it equals a 19% total discount because the second 10% applies to the discounted 90% price ($100 → $90 → $81).

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