How Do You Write Ten Thousands Of An Inch?

Put very simply, you would write ten thousandth of an inch as 0.10. It can also be written as a fraction: 10/1000. There is often a great deal of confusion when it comes to dealing with ‘tenths’ of inches. The exact decimal length of all measurements tends to vary slightly depending on which context you are referring to. People often get confused because those who work in engineering and machinery have a slightly different way of saying one ten thousandth of an inch.
0.0100 is referred to as ten thousandth of an inch, however, machinists often refer to 0.0001 as a tenth. Another reason people get confused is because they refer to ten thousandth of an inch as one ten thousandth of an inch which is 0.0001. Traditionally a "tenth" of an inch is 0.1, which is correct for those of you who do not work in engineering. In manufacturing, a "tenth" is .0001" or one-ten thousandths of an inch which is shortened to a "tenth" for ease of referencing.
The American system of measurement, the Imperial system, often called the Standard English Measurement (SEM) is based on dividing any unit of measure in half instead of dividing a unit of measure by ten which is done in the metric system. The Imperial System commonly works with fractions but these can be converted into decimals but can only be broken down as small as sixty fourths.
If you hear ten thousandth of an inch being said and are confused as to what they are referring to, then put it into context and think about it logically. A newsreader who is quoting how much rain a State going through a drought has received is not going to mean one ‘tenth’ to be 0.0001 inches. It is all about switching the two slightly different meanings to suit the situation.
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There is always confusion when dealing with a "tenth" of an inch.  In manufacturing and measurement where nearly all measurements are expressed in "thousandths" and sometimes mils (equal to .001" to confuse even more).

Traditionaly a "tenth" of an inch is 0.1"
In manufacturing a "tenth" is .0001" or one-ten thousandths of an inch.  It is shortened to  a "tenth"

Where as:
0.100  is one hundred thousandths (of an inch)
0.010 is ten thousandths (of an inch)
0.001 is one thousandths (of an inch)
0.0001 is one-tenth of a thousandths or what a machinists or mechanical engineer would say "one tenth" for short.

You need to understand who you are talking to and the context of the conversation.  The weather man will say that "we received a "tenth" of an inch of rain last night".  He is saying we received 0.1" of rain not .0001" of rain.
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Great answer!  The previous answer trail has been pretty funny to read the mis-understanding of this topic.  If I may expand more I'll show how the naming convention changes as digits move to the left.  Please follow the progression from the bottom-up on the list below:

1.0000
0.9000  is 900-thousandths
0.1000  is 100-thousandths  (one hundred thousandths)
0.0900 is  90-thousandths (ninety thousandths)
0.0100 is 10-thousandths  (ten thousandths)
0.0090 is 9-thousandths (nine thousandths)
0.0010 is 10-ten thousandths OR one thousandths
0.0009 is 9-ten thousandths
0.0001 is 1-ten thousandths OR one-tenth is your a machinist
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Put simply without any explanation one ten-thousands of an inch is written as .010

The American system of measurement is the is based on dividing any unit of measure in half as opposed to dividing a unit of measure by ten as in the metric system.  The American system of measurement was originally called the Imperial measurement system also known as Standard English Measure (SEM)  now known as SAE after the Society of Automotive Engineers. The American system is fractional in nature and can be broken into as many decimal places as desired but is generally only broken down as far as sixty-fourths.

The American system can be defined by dividing the numerator in half as follows.

One inch = 1.000 or  1"
one half = .500 or 1/2"
one quarter =.250 or 1/4"
one eighth = .125 or 1/8"
one sixteenth = .0625 0r 1/16"
one thirtysecond = .03125 or 1/32"
one sixty fourth = .015625 or 1/64"

hence any object can be defined by multiplying the numerator. The american Monetary system is a prime example.
One Dollar = \$1.00
three quarters = \$ .75
Half Dollar = \$.50
one quarter =  \$.25
one dime = \$.10
one Nickle =.05
one penny = .01
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Let's be a little more precise. Your question is silly and has no answer but here are answers to two similar questions.
Ten thousands of inches is written 10,000-inch.
Ten thousandths of an inch is written .010-inch.

1/1000 = .001
10/1000 = .010

1/10,000 = .0001
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Anonymous commented
one thousandth of an inch is .001-inch. (ten of these add up to .010)
one ten-thousandth of an inch is .0001-inch.
Anonymous commented
I agree with RAP. The question in itself isn't very clear. It leans towards the possible .0001 for (1) 10 thousaniths of an inch. forgive my spelling-I'm not sure which is correct.
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(1) ten thousandth = 0.0001
(2) ten thousandths = 0.0002
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.001 is one thousandth and .0001 is one ten thousandth. What you wrote and the number you gave do not correspond is all. You wrote .0010 and the number you showed was .0001.
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0.010
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.oooo1...=100,000ths

.0001...= 10,000ths

.001 =1,000ths

.01= 100th

.1= 1 tenth

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Just use the metric system and be done with it

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Read the number backwards and ignore the decimal point.

For example, 0.1 backwards and ignoring the decimal is 10. Add a "th".

0.01 backwards and ignoring the decimal = 100. Add a "th". One hundredTH

0.000001 backwards and ignoring the decimal = 1 000 000. Add the th. One millionTH

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If:
0.100 is one tenth
0.010 is one hundredth
0.001 is one thousandth
0.010 is ten thousandths   (same as one hundredth)
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1 inch or 1 divided by 10,000 = .0001   simple
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1/8 inches in decimal point
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