Decimal to Fraction Inches Calculator

Turn decimal inches or millimeters into the nearest fraction of an inch you can find on a tape measure or ruler — to the nearest 1/8, 1/16, 1/32 or 1/64.

More decimal and fraction tools

How to use the Decimal to Fraction Inches Calculator

Enter the measurement in decimal inches, millimeters or centimeters.
Choose the precision — 1/16 inch matches most tape measures.
Read the fraction and how far it is from the exact value.

How it works

The measurement is converted to inches (mm ÷ 25.4), multiplied by the chosen denominator, rounded to a whole number and simplified. For 0.6875 in at 1/16 precision: 0.6875 × 16 = 11, so the answer is 11/16″. The rounding error shows how far the fraction is from the exact size — useful when deciding whether 1/16 is precise enough.

How to convert decimal inches to a fraction

A tape measure cannot show 0.55 inch, but it can show sixteenths. To convert a decimal inch to the nearest fraction:

Separate the whole inches. 2.9″ is 2″ plus 0.9″.
Multiply the decimal part by the precision you need — 16 for sixteenths, 32 for thirty-seconds. 0.9 × 16 = 14.4.
Round to the nearest whole number and put it over that denominator: 14/16.
Simplify: 14/16 = 7/8, so 2.9″ ≈ 2 7/8″.

Decimal inches to the nearest 1/16
Decimal	Nearest 1/16	Fraction as decimal	Error
0.3″	5/16″	0.3125″	+0.0125″
0.55″	9/16″	0.5625″	+0.0125″
0.81″	13/16″	0.8125″	+0.0025″
1.47″	1 1/2″	1.5″	+0.03″
2.9″	2 7/8″	2.875″	−0.025″

Which precision should you use?

1/8 inch is fine for rough carpentry and fabric. 1/16 inch matches the smallest marks on most tape measures and is the usual choice for woodworking and DIY. 1/32 inch appears on steel rules and in cabinetry, and 1/64 inch is used for drill bits and machining. Use the coarsest precision that keeps the rounding error acceptable — the calculator shows the error so you can decide.

If the decimal came from an exact fraction (for example a plan that says 0.4375″), it will convert with zero error: 0.4375″ is exactly 7/16″. The full list of exact values is in the decimal to fraction chart, which covers every 64th.

Millimetres to inch fractions

Metric measurements convert the same way after dividing by 25.4 (there are exactly 25.4 mm in an inch). Choose Millimeters in the calculator, or use the table below for common sizes.

Millimetres to the nearest 1/16 inch
Millimetres	Inches	Nearest 1/16
3 mm	0.1181″	1/8″
6 mm	0.2362″	1/4″
10 mm	0.3937″	3/8″
12 mm	0.4724″	1/2″
19 mm	0.748″	3/4″
25 mm	0.9843″	1″

For full conversions between the two systems, see the mm to inches converter. For exact (not rounded) fractions of any decimal, use the decimal to fraction calculator.

Reading fractions on a tape measure

On an imperial tape the longest lines mark whole inches, then half inches, quarter inches, eighths and — the shortest lines — sixteenths. Counting sixteenths from the last whole inch gives the fraction directly: the eleventh small mark after 3″ is 3 11/16″. Many tapes print the common fractions or highlight every 16 inches for stud spacing.

Inch fractions to decimals and millimeters

Fraction	Inches	mm
1/16″	0.0625	1.59
1/8″	0.125	3.18
3/16″	0.1875	4.76
1/4″	0.25	6.35
5/16″	0.3125	7.94
3/8″	0.375	9.53
7/16″	0.4375	11.11
1/2″	0.5	12.7
9/16″	0.5625	14.29
5/8″	0.625	15.88
11/16″	0.6875	17.46
3/4″	0.75	19.05
13/16″	0.8125	20.64
7/8″	0.875	22.23
15/16″	0.9375	23.81
1/1″	1	25.4

Frequently asked questions

What fraction is 0.3 inches?

About 5/16″ (0.3125″) to the nearest 1/16.

What is 10 mm as an inch fraction?

10 mm = 0.3937″, about 25/64″, or 3/8″ to the nearest 1/8.

How do I read a tape measure?

The longest lines are inches, then halves, quarters, eighths and the shortest are sixteenths.

What is 0.75 inches as a fraction?

3/4″.