How to use the chart: two quick examples
The chart works both ways. Start from a fraction to get its decimal, or start from a decimal to find its fraction.
A drill bit is marked 5/16 inch. How many inches is that as a decimal?
The working
- Find 5/16 in the Inches column. It’s in the first half of the chart, with the 16ths in semibold.
- Read across: the decimal is 0.3125, and the size is 7.938 mm.
Answer: 0.3125 inch (about 7.938 mm)
Your calculator shows 0.4375. What fraction is that?
The working
- Find 0.4375 in the Decimal column.
- Read the fraction on the same row: 7/16.
Not on the chart? Type it in the box at the top of the chart. For 0.3 it shows the closest row, 19/64 = 0.296875. In plain fractions, 0.3 is 3/10.
Answer: 7/16
No chart? Divide the top by the bottom
Every fraction is a division problem. The top number goes first.
So 3/8 is 3 ÷ 8 = 0.375. On the GED calculator, that’s 3, the ÷ key, 8. On paper, it’s long division with a decimal point after the 3.
Some decimals stop, and some go on forever. Here’s why: if the bottom number breaks down into only 2s and 5s, the decimal stops. That’s why every 64th stops. Anything else repeats, like 1/3 = 0.333…
That’s what the thirds, fifths and twelfths table is for. A bar over a digit means it repeats, and the rounded value is the one to use in a word problem.
3 mistakes that cost points
Mistake 1: dividing the wrong way
8 ÷ 3 = 2.666… is the wrong answer for 3/8. A fraction smaller than 1 always gives a decimal smaller than 1. If yours is bigger than 1, flip the division.
Mistake 2: losing a zero
1/16 is 0.0625. Writing 0.625 makes it 10 times too big, and 0.625 is 5/8. Check the chart: both are on it, on very different rows.
Mistake 3: writing 1/3 as 0.3
0.3 is 3/10, a little less than 1/3. Use 0.333 (or keep the fraction) until the last step, then round the way the question asks.
Keep going
How to calculate percentages
Turn a fraction or decimal into a percent, and find a percent of any number.
Fractions, decimals and percents practice
25 GED-style questions with new numbers every time and the working shown.
Metric conversion chart
Inches to centimeters and every other factor, with the exact ones marked.
Math formula sheet
Every GED-level formula with a worked example, on two printable pages.
GED math worksheets
Print a new worksheet on any topic, with the answer key on its own page.
Written by
Coach Crissy
Math instructor
Coach Crissy teaches the video lessons behind the BooknBoost GED math course, working through GED-style problems on camera: ratios and proportions, percent and interest, mean, median and mode, slope, and the geometry students meet on test day.