Drafting calculations: converting fractional inches to decimal inches In practical engineering drawing and shop measurements, how do you convert a length written as a fraction of an inch (for example, 5/32 inch) into decimal inches so it can be entered into calculators or CAD software?

Introduction / Context:
Fabrication drawings, machining notes, and CAD inputs frequently require decimal-inch values even when shop practices or legacy prints show fractional inches. Knowing the direct method to convert a fraction (such as 3/16 inch) into decimal inches is a basic but essential drafting and manufacturing skill.

Given Data / Assumptions:

• A measurement is expressed as a fraction a/b inch, where a is the numerator and b is the denominator.
• We want the equivalent value in decimal inches for calculator entry or tolerance stacking.
• No metric conversion is requested at this stage.

Concept / Approach:
The decimal-inch value is simply the numerical value of the fraction. Compute a/b with ordinary division to obtain a decimal (for example, 3/16 = 0.1875). This is independent of any scale or chart. If metric is later required, multiply the decimal inches by 25.4 to obtain millimeters.

Step-by-Step Solution:

Verification / Alternative check:
Cross-check with a standard fractional–decimal table: values like 1/8 = 0.125, 3/16 = 0.1875, 5/16 = 0.3125 confirm the computation.

Why Other Options Are Wrong:

• Look on a metric conversion chart: That converts inches to millimeters, not fractions to decimal inches.
• Check the engineer's scale: A scale helps measure length on paper; it does not convert numeric fractions to decimals.
• All of the above: Incorrect because only direct division is universally correct for fraction-to-decimal conversion.

Common Pitfalls:
Rounding too early can accumulate error in tolerance stacks. Keep at least four decimal places (0.0001 inch) during calculations, then round per drawing precision.

Final Answer:
divide the numerator (top number) by the denominator (bottom number)