1 over 8 as a decimal is 0.125. You get this by dividing 1 by 8, and the result is a clean, terminating decimal with exactly three digits after the decimal point.
How to Calculate 1 ÷ 8
Since 8 doesn’t go into 1, you need to work with decimal places. The simplest way to see it: 8 goes into 10 once (with 2 left over), then 8 goes into 20 twice (with 4 left over), then 8 goes into 40 exactly five times. That gives you 0.125.
Another approach is to turn the fraction into one with a power of ten in the denominator. Since 8 is 2 × 2 × 2, you can multiply the top and bottom by 125 to get 125/1000, which is just 0.125 written as a fraction. This trick works because 8 × 125 = 1,000.
Why It Doesn’t Repeat
Some fractions produce repeating decimals (like 1/3 = 0.333…), but 1/8 terminates neatly. The rule is straightforward: if a fraction’s denominator breaks down into only 2s and 5s as prime factors, the decimal will always terminate. Since 8 = 2³ and contains no other prime factors, 1/8 ends after three decimal places. Fractions like 1/6 or 1/7 repeat because their denominators contain primes other than 2 and 5.
Percentage Equivalent
To convert 0.125 to a percentage, multiply by 100. That gives you 12.5%. So if someone says “one-eighth of the total,” they mean 12.5%.
Where 1/8 Shows Up in Real Life
Cooking
Recipes frequently call for 1/8 of a cup. That equals 2 tablespoons or 1 fluid ounce (about 30 milliliters). If you don’t have a 1/8 cup measure, just grab a tablespoon and scoop twice.
Rulers and Drill Bits
On a standard inch ruler, 1/8-inch marks are the small lines that divide each quarter inch in half. In machining and construction, 1/8 inch is written as 0.125 inches, and drill bit charts list it exactly that way. Knowing the decimal equivalent matters when you’re switching between fractional and decimal tools.
Stock Prices
Before April 2001, U.S. stock exchanges priced shares in fractions, with 1/8 of a dollar ($0.125) as a common increment. The SEC mandated a switch to decimal pricing between September 2000 and April 2001, ending a system that had been in place for hundreds of years. So a stock that once traded at “25 and 1/8” ($25.125) would now simply display $25.13 or similar.
Quick Reference
- Decimal: 0.125
- Percentage: 12.5%
- Milliliters (cooking): ~30 mL per 1/8 cup
- Inches (machining): 0.125″