RE: STL file format units

Date: Fri Jul 18 2003 - 09:28:55 EEST

Hi all,

As mentioned before, an STL-file is unitless and there no convention.

However, there's a kind of unwritten rule that makes that 99.99% of the STLs
- in inch (mainly in the USA)
- in mm (mainly outside USA)

So when you load an STL and it is 25.4 times too big/small... you know what
is wrong.

Almost all RP-programs expects that an STL is in mm or in inch. Magics shows
an alarm message when you load a part that is suspiciously big or small
(depending of the used unit size)

However, I just saw an STL-file with cm as unit size... (The exception
confirms the rule, as we say over here :-) )


Pieter Bourgaux

Application engineer

Tel +32 16 39 66 66
Fax +32 16 39 66 00

No time to fix a file ? does it for you !
On-line around the clock STL repair and CAD to STL conversion.
"No cure, money back" guarantee.

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-----Original Message-----
From: Bathsheba Grossman []
Sent: Friday, July 18, 2003 12:50 AM
To: rp-ml
Subject: Re: STL file format units

On Thu, 17 Jul 2003, Charles Overy wrote:
> Quick question. Is there any formal set of units in the STL standard? In
> other words is there anywhere that the type of units, inches, meters,
> millimeters are called out? Or is it defacto or by convention in one unit
> another? My understanding is that it is unitless and is usually defined
> when you open the file.

The STL format is unitless, and there is no convention: the person
sending the file has to tell the receiver what unit to use.


Bathsheba Grossman                 phone (831)429-8224, fax (831)460-1242
Sculpting geometry                                
Solidscape prototyping                           
Protein crystals                             

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