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Number foundations · Topic 5 of 15

Converting Fractions, Decimals & Percents

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Math · conversions

Converting Fractions, Decimals & Percents

Fraction to decimal: divide. Decimal to percent: point two places right. Percent to decimal: two places left. Memorize the quarter benchmarks.

01 · Fraction → decimalFraction → decimal: top ÷ bottom
02 · Decimal → percentDecimal → percent: point 2 places right
03 · Memorize1/4 = 25%, 1/2 = 50%, 3/4 = 75%
01

The rules

Fraction → decimal: numerator ÷ denominator must know
Decimal → percent: × 100 (point 2 places right), add % must know
Percent → decimal: ÷ 100 (point 2 places left), drop % must know
Percent → fraction: put it over 100, then simplify must know
Decimal → fraction: digits over the last place value, then simplify
Fraction → percent: divide to a decimal, then × 100
02

Know by heart

1/4 = 0.25 = 25% · 1/2 = 0.5 = 50% · 3/4 = 0.75 = 75% must know
1/10 = 0.1 = 10% · 1/5 = 0.2 = 20% (2/5 = 40%, 3/5 = 60%)
1/8 = 0.125 = 12.5% · 3/8 = 37.5% · 5/8 = 62.5%
1/3 = 0.333… = 33⅓% · 2/3 = 0.666… = 66⅔%
03

Worked examples

7/8 = 7 ÷ 8 = 0.875 = 87.5%
45% = 0.45 = 45/100 = 9/20
58% (0.580) < 0.6 (0.600) < 5/8 (0.625)
04

Into a percent or out of one?

Commonly confused
Decimal → percentPercent → decimal
OperationMultiply by 100Divide by 100
Decimal pointMoves 2 places rightMoves 2 places left
% signAdd itDrop it
Example0.07 → 7%7% → 0.07
05

Common mistakes

0.4 = 40%, not 0.4% — check the direction of the move
7% = 0.07, not 0.7 (add a placeholder zero)
06

Also know

Ordering mixed forms: change all to decimals, then compare
07

More detail

Show 5 more facts
Percent = per hundred: 37% = 37/100
Repeating decimal: digits repeat forever (2/9 = 0.222…)
Over 100% → more than 1 (150% = 1.5); under 1% → < 0.01 (0.5% = 0.005)
Terminates only if the denominator’s primes are 2s and 5s
33⅓% = (100/3) ÷ 100 = 1/3
Pearl

To a percent, the point moves two places right; out of a percent, two places left.

Sources · OpenStax Prealgebra 2e §5.3 Decimals and Fractions · OpenStax Prealgebra 2e §5.1 Decimals (decimal to fraction) · OpenStax Prealgebra 2e §6.1 Understand Percent · Math is Fun — Comparing Fractions (decimal method) · Union Test Prep — HESI A2 Mathematics study guide, p. 3: Decimals and percentages · TSTC Library — HESI A2 guide (Math: "Converting Among Fractions, Decimals, and Percents") · Built from the verified NurseSavvy HESI A2 fact map (facts reviewed 2026-10-16). HESI is a trademark of Elsevier; NurseSavvy is not affiliated with Elsevier.

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