Fraction to Decimal Chart

Fraction to Decimal Chart (1/64 to 1 Inch)

This table lists every fraction from 1/64 inch to 1 inch reduced to lowest terms, along with the exact decimal inch and the millimeter equivalent rounded to two decimal places.

According to the National Institute of Standards and Technology (NIST), the inch has been exactly 25.4 millimeters since July 1, 1959, as announced in Federal Register Notice 59-5442. Ten millimeters (mm) equal one centimeter (cm).

Common Fractions at a Glance

Most tape measures and standard shop tools divide inches into sixteenths rather than sixty-fourths. When working on general layout or carpentry, a compact fraction to decimal chart covering halves, quarters, eighths, and sixteenths gives you the values you need without extra clutter.

Each fraction in this simplified reference represents an exact graduation on a standard fractional ruler. If you need to locate a specific mark, read our guide on ruler measurements.

How to Convert a Fraction to a Decimal

A fraction represents division: the numerator divided by the denominator. To convert any fraction to a decimal, divide the top number by the bottom number using a calculator or long division. For example, 3/8 equals 3 ÷ 8 = 0.375, and 3/4 equals 3 ÷ 4 = 0.75.

When handling a mixed number, keep the whole number intact and convert only the fraction portion. For a measurement such as 2 5/16 inches, divide 5 by 16 to get 0.3125, then add the whole number back to reach 2.3125 inches.

To find the measurement in millimeters, multiply the decimal inch value by 25.4. For 3/8 inch, multiply 0.375 by 25.4 to get 9.525 millimeters exactly, which rounds to 9.53 mm at two decimal places.

Every inch fraction built on halves, quarters, eighths, sixteenths, thirty-seconds, and sixty-fourths creates a terminating decimal. Because 64 equals 2 to the sixth power (2⁶), every fraction with a denominator of 64 resolves to an exact decimal with at most six decimal places.

You can also use a simple halving rule as a calculation shortcut. Every time you cut a fraction in half, you halve the decimal value. One half (1/2) is 0.5. Halving that gives 1/4 = 0.25, followed by 1/8 = 0.125, 1/16 = 0.0625, 1/32 = 0.03125, and 1/64 = 0.015625. Because any eighth is simply a multiple of 0.125, you can calculate 5/8 by evaluating 5 × 0.125 = 0.625. Likewise, 11/16 equals 11 × 0.0625 = 0.6875.

Rounding a Decimal to the Nearest 1/16 Inch

A calculator can return a decimal with six or more digits, but a tape measure reads in sixteenths. You can round any decimal to the nearest sixteenth in four steps.

Multiply the decimal portion by 16, round the result to the nearest whole number, put that whole number over 16, and reduce the fraction to lowest terms.

When a decimal lands precisely halfway between two sixteenths, the math yields a tie. For example, 0.40625 multiplied by 16 equals 6.5 exactly. That value is 13/32 inch, which sits directly between 3/8 inch (6/16) and 7/16 inch (7/16). Standard rounding conventions round half up to 7/16, but practical workshop tasks depend on the fit: choose the smaller or larger size based on whether a tight or loose joint is needed.

To round a millimeter value to the nearest sixteenth of an inch, divide the millimeter value by 25.4 first, then apply the same steps. For a 10 mm measurement, dividing by 25.4 produces 0.3937 inches. Multiplying 0.3937 by 16 gives 6.30, which rounds to 6, yielding 6/16 or 3/8 inch.

Following NIST SP 811, Guide for the Use of the SI (Appendix B), converted measurements should carry no more digits than the precision of the original measuring device. A tape measure reading to the nearest 1/16 inch does not justify six decimal places. When you need to read your measurement directly on a scale, consult our guide on how to read a tape measure.

• 0.3 inches: 0.3 × 16 = 4.8, which rounds to 5, giving 5/16 inch (0.3125).
• 0.43 inches: 0.43 × 16 = 6.88, which rounds to 7, giving 7/16 inch (0.4375).
• 0.6 inches: 0.6 × 16 = 9.6, which rounds to 10, giving 10/16 or 5/8 inch (0.625).
• 0.7 inches: 0.7 × 16 = 11.2, which rounds to 11, giving 11/16 inch (0.6875).
• 0.9 inches: 0.9 × 16 = 14.4, which rounds to 14, giving 14/16 or 7/8 inch (0.875).

Decimal to Fraction Conversions

To turn a decimal value back into an inch fraction, locate the decimal in the center column of the chart and read the corresponding fraction in the left column. For example, a caliper measurement of 0.625 lines up directly with 5/8 inch.

If the decimal number falls between two rows in the chart, choose the level of precision your work requires. For standard tape layout, use the nearest 1/16 rounding rule. For fine work on a machine, multiply the decimal portion by 32 or 64 to find the closest 32nd or 64th increment.

Common questions

How do I convert fractions to decimals?

Divide the numerator by the denominator. For example, 3/8 converts by calculating 3 ÷ 8, which gives 0.375.

What is 3/8 as a decimal?

3/8 inch is exactly 0.375 inches. In metric measurement, 0.375 inches converts to 9.525 millimeters, or 9.53 mm rounded to two decimal places.

What is 3/4 in decimal?

3/4 inch equals 0.75 inches exactly. That corresponds to 19.05 millimeters.

Can you show me a simple fraction/decimal chart?

The Common Fractions at a Glance table lists every sixteenth, including 1/16 (0.0625), 1/8 (0.125), 1/4 (0.25), 1/2 (0.5), and 3/4 (0.75) alongside their millimeter values.

Is there a quick trick to convert fractions to decimals?

Remember that each halving cuts the decimal in half: 1/2 = 0.5, 1/4 = 0.25, 1/8 = 0.125, and 1/16 = 0.0625. Any eighth is a multiple of 0.125, so 5/8 is 5 × 0.125 = 0.625.

How do you memorize fractions as decimals?

Memorize the eighths as multiples of 0.125: 1/8 is 0.125, 2/8 (1/4) is 0.25, 3/8 is 0.375, 4/8 (1/2) is 0.5, 5/8 is 0.625, 6/8 (3/4) is 0.75, and 7/8 is 0.875.

Related

• Ruler Measurements
• How to Read a Tape Measure
• How to Read a Ruler