What is 3.375 inches as a fraction?

3 3/8 inches. The decimal part 0.375 × 8 = 3, so it's 3/8 exactly — no rounding needed.

How do I read the calculator's output as a fraction?

Combine the three fields. Whole Inches = 3, Numerator = 6, Denominator = 16 reads as 3 and 6/16, which simplifies to 3 3/8 by dividing top and bottom by 2.

Which precision should I pick?

16ths for a standard construction tape, 32nds for fine woodworking, 64ths for machining and tool grinding. Most household tapes are marked to 16ths.

What if the decimal doesn't land on an exact fraction?

It rounds to the nearest fraction at your chosen precision. 0.3 inch at 16ths becomes 5/16 (0.3125), the closest sixteenth. The worst-case error is half the smallest division.

How do I simplify the fraction the calculator gives me?

Divide the numerator and denominator by their greatest common divisor. 6/16 → divide by 2 → 3/8. 12/32 → divide by 4 → 3/8. The tool reports the raw fraction so you can see the precision level directly.

Why do rulers use halves, quarters, eighths, and sixteenths?

Repeated halving. Each mark splits the previous one in two, so the denominators are always powers of two. That's also why every fractional inch has a clean, terminating decimal.

Inches to Fraction Calculator

A decimal inch is easy to calculate with and impossible to find on a tape measure. This calculator does the reverse of a fraction-to-decimal conversion: give it 3.375 and a precision level, and it hands back the nearest ruler fraction — 3 3/8 at sixteenths. Woodworkers, machinists, and anyone converting a CAD dimension back to something they can mark on stock use this constantly.

The decimal to fraction formula

where is the chosen denominator (8, 16, 32, or 64). The fraction is then numerator over , simplified by dividing both by their greatest common divisor.

Worked example

The calculator’s defaults are 3.375 inches at sixteenths precision.

So the raw result is 3 and 6/16 inches, which simplifies to 3 3/8 because the greatest common divisor of 6 and 16 is 2.

Inches to Fraction Calculator worked example diagram — A visual read of the worked example above — the same numbers the calculator returns for its default inputs.

What Your Results Mean

The three result fields give you everything needed to write the fractional measurement: Whole Inches is the integer part, Fraction Numerator is the top of the fraction, and Fraction Denominator is the bottom (always equal to your chosen precision). Together, they read as “3 and 6/16 inches.”

Understanding precision levels

Precision	Smallest division	Use case
8ths	0.125 in	Rough carpentry, general layout
16ths	0.0625 in	Standard tape measures, cabinetry
32nds	0.03125 in	Fine woodworking, drill bits
64ths	0.015625 in	Precision metalwork, tool grinding

Maximum rounding error

Your maximum error is half the smallest division: +/-1/32 inch at 16ths precision, +/-1/64 inch at 32nds precision. For most construction work, 16ths is more than adequate. Choose 32nds or 64ths only when tolerance demands it.

If you need to go the other direction and convert a fractional measurement to decimal, use the inches fraction to decimal calculator. For converting your decimal inches to metric units, try the inches to mm converter for precision work or the inches to cm converter for general metric conversion.

Doing it by hand

Multiply the decimal part by the denominator you want, round to the nearest whole number, and simplify. For 2.6875 inches at sixteenths:

That one lands exactly. Most decimals don’t. For 4.3 inches, , which rounds to 5, giving inches (4.3125). The rounding error is inch, well under the 1/32-inch maximum for sixteenths.

Rounding up or down on purpose

The calculator rounds to the nearest fraction, which is right most of the time. Sometimes it pays to round in a set direction:

A part that must fit into a slot should round down, so it never comes out too big.
A hole a bolt or dowel must pass through should round up, so it’s never too tight.
A cut you’ll trim to fit can round up; you can always take more off.

Common mistakes

Leaving the fraction unsimplified. is . Tape measures mark the simplest form, so simplify before you look for the line.
Ending up with 16/16. 2.98 inches rounds to at sixteenths. That’s a whole inch, so the answer is 3 inches, not .
Reading decimal digits as the fraction. 0.5 inch is , not , and 0.25 inch is , not .
Using a finer precision than you can mark. A pencil line is about 1/32 inch wide, so 64ths only help with a knife line or a caliper.

About the formula: The fractional part is found by multiplying the decimal remainder by the chosen denominator and rounding to the nearest whole number.