What is 5/8 inch as a decimal?

Five eighths of an inch is **0.625 inches** as a decimal. That is the decimal inch value of the fraction **5/8** alone (not including whole inches). If you meant **1-5/8 inches**, write it as **1 + 5/8 = 1.625** decimal inches.

How do I convert a mixed fraction like 5-3/16 to a decimal?

Convert the fractional part first: **3/16 = 0.1875**. Add the whole inches: **5 + 0.1875 = 5.1875** decimal inches. Our [Inches to Decimal Tool](https://decimaltools.com/tools/convert-inches-to-decimal) checks this in one step.

Is decimal inches the same as converting inches to metric?

No. **Decimal inches** keeps the unit as inches but expresses the length as a decimal (e.g., **0.375 in**). Converting inches to **millimeters** multiplies by **25.4** (exact definition). Use decimal inches for fractional-inch drawings; use metric when the spec is in mm.

Why do my CAD/CNC numbers differ slightly from hand math?

Rounding, tool offset, and drawing units can differ. Always follow the **lead number** on the print, store full precision internally, and round only at the end to the tolerance shown.

$Tape measure and caliper illustrating fractional inches next to decimal inch values$

Inches to Decimal: A Quick Guide & Conversion Chart

Q: How many decimal places should I use for inches?

It depends on the job. **Woodworking and rough carpentry** often use **3 decimal places** (thousandths of an inch) or match your tape measure. **Machining and CNC** commonly use **4 decimal places** (ten-thousandths) or whatever the print specifies. **Blueprints** may show a tolerance—match the implied precision and never round beyond what the design allows.

People search for inches to decimal when a drawing, CNC program, or DIY cut list uses fractional inches (like 3/8″ or 1-1/4″) but the software, spreadsheet, or machine wants a decimal inch value (like 0.375 or 1.25). That shows up daily in blueprint takeoffs, CNC and CAM, 3D modeling, metalworking, and finish carpentry where small errors are costly.

For instant checks without pencil work, use our online Inches to Decimal Converter—it is built for mixed fractions, stacked fractions, and quick copy-paste results.

The formula (fraction to decimal inch)

For a proper fraction of an inch, the decimal inch value is the fraction converted to a decimal:

$Decimal = \frac{Numerator}{Denominator}$

Examples:

1/4 → $Decimal = \frac{1}{4} = 0.25$ inch
5/16 → $Decimal = \frac{5}{16} = 0.3125$ inch

For a mixed number (whole inches plus a fraction), convert the fraction part with the same rule, then add the whole number:

$Total\ (inches) = Whole + \frac{Numerator}{Denominator}$

After the formula, double-check tricky denominators (16, 32, 64) against the conversion table below—those are the ones people mis-type most often.

Step-by-step: mixed fractions (e.g., $5 \frac{3}{16}$ )

Goal: Turn $5 \frac{3}{16}$ inches into one decimal inch number.

Separate the whole inch and the fraction: 5 and 3/16.
Apply the formula to the fraction: $\frac{3}{16} = 0.1875$ .
Add the whole inches: $5 + 0.1875 = 5.1875$ inches.

Quick sanity check: 3/16 is a bit less than 1/4 (0.25), so 5.1875 should sit between 5.125 and 5.25—it does.

Improper-fraction path: Write $5 \frac{3}{16}$ as $\frac{83}{16}$ (because $5 \times 16 + 3 = 83$ ), then $83 \div 16 = 5.1875$ . Same result.

Comparison table: common fractional inches (1/64″ to 1″)

Use this chart for standard fractional inch sizes. Values are decimal inches for the fraction only (not added to whole inches). For 1-5/8″, add 1.000 to 0.625.

Fraction	Decimal (in)	Fraction	Decimal (in)
1/64	0.015625	33/64	0.515625
1/32	0.03125	17/32	0.53125
3/64	0.046875	35/64	0.546875
1/16	0.0625	9/16	0.5625
5/64	0.078125	37/64	0.578125
3/32	0.09375	19/32	0.59375
7/64	0.109375	39/64	0.609375
1/8	0.125	5/8	0.625
9/64	0.140625	41/64	0.640625
5/32	0.15625	21/32	0.65625
11/64	0.171875	43/64	0.671875
3/16	0.1875	11/16	0.6875
13/64	0.203125	45/64	0.703125
7/32	0.21875	23/32	0.71875
15/64	0.234375	47/64	0.734375
1/4	0.25	3/4	0.75
17/64	0.265625	49/64	0.765625
9/32	0.28125	25/32	0.78125
19/64	0.296875	51/64	0.796875
5/16	0.3125	13/16	0.8125
21/64	0.328125	53/64	0.828125
11/32	0.34375	27/32	0.84375
23/64	0.359375	55/64	0.859375
3/8	0.375	7/8	0.875
25/64	0.390625	57/64	0.890625
13/32	0.40625	29/32	0.90625
27/64	0.421875	59/64	0.921875
7/16	0.4375	15/16	0.9375
29/64	0.453125	61/64	0.953125
15/32	0.46875	31/32	0.96875
31/64	0.484375	63/64	0.984375
1/2	0.5	1	1.0

Skip the manual math! Use our Inches to Decimal Tool for instant, error-free results.

Why this search happens (user intent)

Blueprints and specs mix fractional callouts with software that wants decimals.
CNC, CAM, and laser workflows often import decimal inch or G-code positions.
DIY and remodeling use tape measures in eighths/sixteenths, while cut lists or IKEA-style instructions may use decimals.
Education and trades training need a reliable method and a lookup for quizzes and job sites.

FAQ

What is 5/8 as a decimal?

5/8 inch = 0.625 inch as a decimal. If your measurement is 2-5/8 inches, it is 2 + 0.625 = 2.625 decimal inches.

How many decimal places should I use for inches?

Match the job: three decimals are common for general work; four for tighter machining; always follow the print tolerance if one is given.

Does this page replace a calculator?

It gives the method and a chart. For arbitrary fractions or stacked inputs, use the online Inches to Decimal Converter linked above.

Bottom line: Convert any inch fraction with $Decimal = Numerator \div Denominator$ , then add whole inches for mixed numbers. Keep one trusted chart or converter handy so blueprint → machine stays accurate on the first try.