Converting Fractions to Decimals Mentally

Fraction-Decimal Conversion Shortcuts

Many common fractions have simple decimal equivalents worth memorizing.

Halves, Quarters, Eighths

Halves:

• 1/2 = 0.5
• 1½ = 1.5

Quarters:

• 1/4 = 0.25
• 2/4 = 1/2 = 0.5
• 3/4 = 0.75

Eighths:

• 1/8 = 0.125
• 3/8 = 0.375
• 5/8 = 0.625
• 7/8 = 0.875

Pattern: Add 0.125 each time!

Thirds and Sixths

Thirds:

• 1/3 = 0.333... (repeating)
• 2/3 = 0.666... (repeating)

Sixths:

• 1/6 = 0.1666...
• 5/6 = 0.8333...

Fifths and Tenths

Fifths:

• 1/5 = 0.2
• 2/5 = 0.4
• 3/5 = 0.6
• 4/5 = 0.8

Pattern: Multiply numerator by 2, put decimal point!

Tenths:

• 1/10 = 0.1
• 3/10 = 0.3
• 7/10 = 0.7

Direct: n/10 = 0.n

Ninths (Special Pattern)

• 1/9 = 0.111...
• 2/9 = 0.222...
• 3/9 = 1/3 = 0.333...
• 4/9 = 0.444...
• 5/9 = 0.555...

Pattern: n/9 = 0.nnn... (repeating)

Percentages to Decimals

Move decimal left 2 places:

• 25% = 0.25
• 7.5% = 0.075
• 150% = 1.50

Quick Reference Table

Fraction	Decimal	Percentage
1/2	0.5	50%
1/3	0.333...	33.33%
1/4	0.25	25%
1/5	0.2	20%
1/8	0.125	12.5%
1/10	0.1	10%
3/4	0.75	75%
2/3	0.666...	66.67%

Converting Any Fraction

Method: Divide numerator by denominator

Example: 3/8

• 3 ÷ 8 = 0.375
• Or remember: 1/8 = 0.125, so 3/8 = 3 × 0.125 = 0.375

Example: 7/20

• Think: 7/20 = 35/100 = 0.35
• Or: 7 ÷ 20 = 0.35