Convert Inches to Thou
1 inch is 1,000 thou. One inch is exactly 1000 thou.
One inch is 1000 thou. To convert inches to thou, multiply by 1000; to go the other way, divide by 1000 or multiply by 0.001. The factor is exact rather than rounded: it follows from NIST. Exactly 25.4 millimeters since the 1959 international yard and pound agreement, and one twelfth of a foot.
Factor checked against the defining standard · How we check
- Inches × 1000
1 * 10001,000 thou
1 inch in every length unit
| Unit | Value | Exact factor |
|---|---|---|
| inches (as entered) | 1 in | — |
| feet | 0.08333333333 ft | × 0.0833333333333 |
| yards | 0.02777777778 yd | × 0.0277777777778 |
| miles | 0.00001578282828 mi | × 0.0000157828282828 |
| millimeters | 25.4 mm | × 25.4 |
| decimetres | 0.254 dm | × 0.254 |
| centimeters | 2.54 cm | × 2.54 |
| meters | 0.0254 m | × 0.0254 |
| kilometers | 0.0000254 km | × 0.0000254 |
| nautical miles | 0.00001371490281 nmi | × 0.0000137149028078 |
| micrometers | 25,400 µm | × 25,400 |
| nanometers | 25,400,000 nm | × 25,400,000 |
| thou | 1,000 thou | × 1,000 |
Factors are entered by hand from NIST rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert inches to thou? The converter and the working
- 1.Take the measurement in inches.
- 2.Multiply by 1000 — that is how many thou fit in one inch.
- 3.To go back the other way, divide by 1000, or multiply by 0.001.
Worked example: 25 inches to thou
- Formula
- in × 1000 = thou
- Arithmetic
- 25 × 1000 = 25,000 thou
- Answer
- 25 in = 25,000 thou
The factor is exact, so this figure is exact too — only the display is rounded.
Inches to thou conversion table
| Inches | Thou |
|---|---|
| 1 in | 1,000 thou |
| 2 in | 2,000 thou |
| 3 in | 3,000 thou |
| 4 in | 4,000 thou |
| 5 in | 5,000 thou |
| 6 in | 6,000 thou |
| 7 in | 7,000 thou |
| 8 in | 8,000 thou |
| 9 in | 9,000 thou |
| 10 in | 10,000 thou |
| 12 in | 12,000 thou |
| 15 in | 15,000 thou |
| 20 in | 20,000 thou |
| 25 in | 25,000 thou |
| 50 in | 50,000 thou |
| 100 in | 100,000 thou |
| 200 in | 200,000 thou |
| 300 in | 300,000 thou |
| 500 in | 500,000 thou |
| 1000 in | 1,000,000 thou |
| 2000 in | 2,000,000 thou |
| 5000 in | 5,000,000 thou |
| 10000 in | 10,000,000 thou |
What is an inch?
Exactly 25.4 millimeters since the 1959 international yard and pound agreement, and one twelfth of a foot.
What is a thou?
A thousandth of an inch, exactly 25.4 micrometers, and called a mil in American workshops — the same word the metric world uses for a millimeter, which is why a drawing marked "5 mil" is worth checking twice.
How many thou are in an inch?
One inch is 1000 thou, exactly. Going the other way, one thou is 0.001 inches. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every length unit here
The whole group — 13 units with their symbols and the size of each one in meters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to an inch.
Source: NIST — international yard and pound agreement (inch = 25.4 mm exactly)
Cite this page
- APA
- Rule Calculator. (2026). Convert Inches to thou. Rule Calculator. https://rulecalculators.com/convert/inch-to-thou
- MLA
- "Convert Inches to thou." Rule Calculator, August 16, 2026, https://rulecalculators.com/convert/inch-to-thou.
- Chicago
- Rule Calculator. "Convert Inches to thou." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/inch-to-thou.
The date is when the figures on this page were last checked against their source, not the day you opened it. Add your own access date if your style needs one.
Questions people actually ask
- How many thou are in an inch?
- 1000. A thousandth of an inch, exactly 25.4 micrometers, and called a mil in American workshops — the same word the metric world uses for a millimeter, which is why a drawing marked "5 mil" is worth checking twice.
- How do I convert thou back to inches?
- Divide by 1000, or multiply by 0.001 — they are the same operation.
Other length conversions
Thou to inches — the same conversion the other way.