Inches to Decimal Calculator
Inch measurement to convert
Enter inches as a decimal like 5.375, or a fraction like
5 3/8 or 3/8.
Decimal inches
awaiting inputAwaiting input.
Enter an inch measurement to convert.
- Nearest fraction (1/16")
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- Feet & inches
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- Millimetres
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- Centimetres
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An inch measurement can be written as a decimal, a fraction, or feet and inches — this calculator converts between all of them at once. 5 3/8" equals 5.375", 136.525 mm, and 0' 5.375" — the same length, four different notations.
Decimal, Fraction or Feet-and-Inches
The same physical length can be written three different ways depending on the tool and trade — and converting between them is the single most common measurement task in construction, machining and design.
A decimal inch, like 5.375", is what a caliper, spreadsheet or CAD program expects. A fractional inch, like 5 3/8", is what a tape measure or ruler physically shows. Feet and inches, like 0' 5.375" or 4' 2", is how longer building and framing measurements are conventionally recorded on site. All three describe the identical length — only the notation changes.
Converting Between Every Unit
Three formulas take a decimal inch value to feet, millimetres and centimetres.
V is the decimal inch value. MM multiplies it by the exact 25.4 mm-per-inch factor. FT is the whole number of feet contained in V, found by integer division.
- VThe input length in decimal inches, such as 5.375.
- MMMillimetres: V × 25.4.
- CMCentimetres: MM ÷ 10.
- FTWhole feet contained in V, found by dividing by 12 and discarding the remainder.
Worked calculation — 5.375"
- 5.375 × 25.4 = 136.525Millimetres
- 136.525 ÷ 10 = 13.6525Centimetres
- 5.375 ÷ 12 = 0 remainder 5.375Feet and inches
5.375" = 136.525 mm = 13.6525 cm = 0' 5.375"
Common Inch Measurements in Every Unit
The inch lengths that come up constantly in framing, furniture and site work.
| Decimal inches | Feet & inches | Millimetres | Centimetres |
|---|---|---|---|
| 0.5" | 0.5" | 12.7 mm | 1.27 cm |
| 1" | 1" | 25.4 mm | 2.54 cm |
| 6" | 6" | 152.4 mm | 15.24 cm |
| 12" | 1' 0" | 304.8 mm | 30.48 cm |
| 18" | 1' 6" | 457.2 mm | 45.72 cm |
| 24" | 2' 0" | 609.6 mm | 60.96 cm |
| 36" | 3' 0" | 914.4 mm | 91.44 cm |
Converting Without a Calculator
- For millimetres, multiply by 25.4. 8" × 25.4 = 203.2 mm.
- For feet, divide by 12 and keep the remainder as leftover inches. 50" ÷ 12 = 4 remainder 2, so 4' 2".
- For a fraction, round the decimal part to the nearest sixteenth or your chosen precision. 0.375 × 16 = 6, so 3/8".
Frequently Asked Questions
How many millimeters are in an inch?
Exactly 25.4 millimetres. This has been the official, exact definition of an inch since the international yard and pound agreement of 1959 — it isn't a rounded approximation.
How do I convert inches to feet?
Divide the number of inches by 12. The whole-number part of the result is the number of feet, and the remainder is the leftover inches. 50 inches ÷ 12 = 4 remainder 2, so 50" is 4' 2".
What is 5.375 inches as a fraction?
5.375" is 5 3/8". The fractional part, 0.375, equals 3/8 exactly, since 0.375 × 8 = 3 with no remainder.
How many decimal places should I use for inches?
It depends on the trade. General construction and woodworking rarely need more than two decimal places (0.01"). Machining and metalworking typically work to three or four decimal places (0.001"–0.0001"), matching the resolution of a caliper or micrometer.
What's the difference between imperial and metric length measurement?
Imperial units — inches, feet, yards — are standard in US construction, woodworking and everyday measurement. Metric units — millimetres, centimetres, metres — are standard almost everywhere else and across most engineering and scientific work worldwide. Converting between the two systems always uses the same fixed factor: 1 inch = 25.4 mm exactly.
Decimal & Inch Tools
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