Decimal to Inches Calculator

Introduction

A tape measure does not show numbers like 5.375. It shows marks like 1/2, 1/4, 1/8, and 1/16. This decimal to inches calculator turns your decimal number into a fraction you can find on a ruler.

Type in a value, pick your unit, and the answer appears as you type. You can enter inches, feet, yards, millimeters, centimeters, or meters. The tool shows the exact fraction, the closest fraction at the precision you pick (1/4 up to 1/64), the feet-and-inches form, and metric sizes too.

You can also choose to round up, round down, or to the nearest mark. Round up when you need extra room. Round down when you plan to cut or sand material away. The calculator tells you how far off the rounded answer is, so you know if the fit will work.

There is a picture of a ruler that shows where your value lands, step-by-step math so you can see how it works, and a full chart of fractions from 1/64 to 1 inch. It helps with woodworking, metal work, sewing, 3D printing, and any job where numbers meet a tape measure.

How to use our Decimal to Inches Calculator

Type a decimal measurement, pick how fine you want the fraction, and the calculator shows it as an inch fraction, feet and inches, metric sizes, and the rounding error.

Decimal value: Type your number in the box, like 5.375. Use digits and one decimal point only. Results update as you type.

Unit: Pick the unit of the number you typed: in, ft, yd, mm, cm, or m. The tool changes it to decimal inches first, then to a fraction.

Quick examples: Click any example button to load a common decimal inch value and see how it works.

Fractional precision: Choose 1/4, 1/8, 1/16, 1/32, or 1/64. This is the smallest mark on your ruler or tape. Smaller fractions give a closer answer.

Rounding direction: Pick Nearest for the closest mark, Round Up so the answer is never smaller than your value, or Round Down so it is never larger.

Offset unit: Choose inches, thou, mm, or cm to show how far the rounded fraction sits from your exact value.

Calculate and Reset: Press Calculate to run the numbers again, or Reset to return to the default 5.375 inches at 1/16 precision.

Decimal to Inches Conversion Explained

A tape measure does not show numbers like 5.375. It shows marks like 1/2, 1/4, 1/8, and 1/16. Converting decimal to inches means turning a decimal number, such as 5.375, into a fraction you can actually find on a ruler. In this case, 5 3/8 inches.

How the Math Works

Every inch is split into equal parts. To change a decimal into a fraction, you multiply the decimal by the number of parts, then round to a whole number. That whole number becomes the top of the fraction.

Example with 5.375 inches at 1/16 precision:

0.375 × 16 = 6
So the fraction is 6/16
6/16 reduces to 3/8
Final answer: 5 3/8 inches

Reducing means dividing the top and bottom by the same number. Both 6 and 16 divide by 2, which gives 3/8. It is the same size, just written in a simpler way.

Common Decimal to Fraction Inch Values

0.0625 in = 1/16 in
0.125 in = 1/8 in
0.25 in = 1/4 in
0.375 in = 3/8 in
0.5 in = 1/2 in
0.625 in = 5/8 in
0.75 in = 3/4 in
0.875 in = 7/8 in

Picking a Precision

Precision is how fine the ruler marks are. A standard tape measure goes down to 1/16 inch. Machine shop rules and dial calipers often go to 1/32 or 1/64 inch. Pick the smallest fraction your tool can actually read. Using 1/64 on a tape measure that only shows 1/16 will not help you.

Rounding Up or Down

Most decimals do not land exactly on a ruler mark. You have to round, and the direction matters:

Nearest picks the closest mark. Good for most layout and framing work.
Round up means the answer is never smaller than your number. Use this when you need a hole or gap that things must fit through.
Round down means the answer is never bigger. Use this when cutting material you can always trim more off, or for a tight press fit.

The gap between your real number and the rounded fraction is called the rounding error, or fitment offset. It is often shown in thou (one thou = 0.001 inch). A small offset is fine for wood. Metal parts usually need a much smaller one.

Inches, Feet, and Metric

These conversions are fixed and never change:

1 inch = 25.4 mm
1 inch = 2.54 cm
1 foot = 12 inches
1 yard = 36 inches

To turn decimal inches into feet and inches, divide by 12. The whole number is the feet. The leftover is the inches. For example, 30.5 inches ÷ 12 = 2 feet with 6.5 inches left over, or 2 feet 6 1/2 inches.

Where You Use This

Decimal inches show up in CAD drawings, CNC files, digital calipers, spec sheets, and calculator screens. Fractions show up on tape measures, drill bits, wrenches, and lumber sizes. Converting between them is a daily job in woodworking, metalwork, construction, plumbing, and 3D printing.

Formulas used

Convert entry to decimal inches

d = v \times k_u,\quad k_{\text{in}}=1,\; k_{\text{ft}}=12,\; k_{\text{yd}}=36,\; k_{\text{mm}}=\tfrac{1}{25.4},\; k_{\text{cm}}=\tfrac{1}{2.54},\; k_{\text{m}}=\tfrac{1000}{25.4}

Exact fraction from the decimal (GCD reduction)

d = w + \frac{N}{10^{p}} = w + \frac{N \div g}{10^{p} \div g},\quad g = \gcd\!\left(N,\,10^{p}\right)

Rounding to 1/D of an inch

n = \mathrm{round}(d \cdot D),\quad n = \lceil d \cdot D \rceil \ (\text{up}),\quad n = \lfloor d \cdot D \rfloor \ (\text{down})

Rounded value as a reduced fraction

x = \frac{n}{D} = \left\lfloor \frac{n}{D} \right\rfloor + \frac{r \div g}{D \div g},\quad r = n - D\left\lfloor \frac{n}{D} \right\rfloor,\; g=\gcd(r,D)

Fitment offset (rounding error)

\Delta = d - x = d - \frac{n}{D}

Feet and inches from the rounded result

F = \left\lfloor \frac{n}{12D} \right\rfloor,\quad I = \left\lfloor \frac{n - 12DF}{D} \right\rfloor,\quad f = \frac{n - 12DF - DI}{D}

Metric and decimal-feet equivalents

\text{mm} = d \times 25.4,\quad \text{cm} = d \times 2.54,\quad \text{m} = d \times 0.0254,\quad \text{ft} = \frac{d}{12}

Frequently asked questions

How many 1/16ths are in one inch?

There are 16. An inch is cut into 16 equal parts on a standard tape measure.

2 halves = 1 inch
4 quarters = 1 inch
8 eighths = 1 inch
16 sixteenths = 1 inch
32 thirty-seconds = 1 inch
64 sixty-fourths = 1 inch

So 8/16 is the same as 1/2, and 4/16 is the same as 1/4.

What is 0.1 inches as a fraction?

The exact fraction is 1/10 of an inch, but no ruler has that mark.

On a tape measure, the closest mark is 1/8 inch (0.125). That is 0.025 inch too big. If your tool reads 1/64ths, 6/64 (which reduces to 3/32, or 0.09375) is much closer.

What is 10 mm in inches as a fraction?

10 mm is 0.3937 decimal inches. The closest common fraction is 25/64 inch (0.3906 in).

On a normal tape measure that only shows 16ths, use 3/8 inch (0.375 in). That is about 0.5 mm small, so check if that gap matters for your job.

What is a thou in measuring?

A thou (also called a mil) is one thousandth of an inch, or 0.001 inch. It equals 0.0254 mm.

A sheet of printer paper is about 4 thou thick. Machinists use thou to talk about tight fits, because inch fractions are too big for that kind of work.

How do you convert decimal feet into feet and inches?

Keep the whole number as feet. Multiply the leftover decimal by 12 to get inches.

Example: 5.75 feet

5 feet stays as 5 feet
0.75 × 12 = 9 inches
Answer: 5 feet 9 inches

If the inches come out with a decimal, turn that part into a fraction the same way you would any decimal inch.

What is the smallest mark on a standard tape measure?

Most tape measures in the United States go down to 1/16 inch. That is 0.0625 inch.

Some longer tapes only show 1/8 inch marks past the first foot. Steel rules, machinist scales, and calipers can read 1/32 or 1/64 inch. Always pick the precision your own tool can actually show.

Why can't some decimals be written as an exact inch fraction?

Ruler fractions only use bottoms that double: 2, 4, 8, 16, 32, 64. A decimal fits exactly only if it can be written over one of those numbers.

0.375 works, because it equals 6/16. But 0.1, 0.3, and 1/3 never land on a mark, no matter how fine the ruler is. For those you pick the closest mark and accept a tiny gap.

What is 3/4 inch in millimeters?

3/4 inch equals 19.05 mm.

The math: 3 ÷ 4 = 0.75 inch, then 0.75 × 25.4 = 19.05 mm. One inch is always exactly 25.4 mm, so you can use that same step for any fraction.

How do you turn an inch fraction back into a decimal?

Divide the top number by the bottom number.

1/2 = 1 ÷ 2 = 0.5 in
5/8 = 5 ÷ 8 = 0.625 in
7/16 = 7 ÷ 16 = 0.4375 in
1/64 = 1 ÷ 64 = 0.015625 in

This is what you need when you type a tape measure number into a CAD file or a CNC program.

Which is bigger, 7/16 or 1/2 of an inch?

1/2 is bigger. Change both to decimals to see it: 7/16 = 0.4375 and 1/2 = 0.5.

The gap is 1/16 inch, or 0.0625 inch. A quick trick is to give both the same bottom number: 7/16 versus 8/16.

What do the ' and " symbols mean in measurements?

One mark (') means feet. Two marks (") means inches.

So 6' 2" reads as six feet two inches. You may also see 6 ft 2 in written out. Mixing them up is a common and costly mistake on cut lists.

How much rounding error is okay when cutting?

It depends on the material and the job.

Framing and rough carpentry: 1/16 inch (about 62 thou) is fine.
Fine woodworking and trim: aim for 1/32 inch or better.
Metal and machine parts: often 5 thou or less, so use decimals, not fractions.

Small errors add up. If you cut ten parts each 1/16 inch short, you lose over half an inch across the run.