What Is The Difference Between STL & STEP Files? (Explained)

I have been working with STL(.stl) & STEP (.stp) files as part of my design engineering CAD profession for nearly 15 years now. In that time, I have learned (often the hard way) the benefits and disadvantages of each CAD file type and when to use each type for specific design and manufacturing tasks.

The main difference between STL & STEP files from a CAD user’s view is the amount of data stored in the files and what can be done with that data. STL files have a small file size, perfect for 3D printing, however, they are not easy to modify or edit with most CAD packages

From my experience, I will give examples of exactly what this means, how I use STL and STEP files as a professional engineer, and how you can know when to pick the right file type for your task.

In this article I will cover:

  • What is the difference between STL and STEP files?
  • Is STL a STEP file?
  • Can a 3D printer read STEP files?
  • What is a STEP file used for?
  • What is an STL file used for?
  • When to use a Step or STL File?
  • Can I Convert a STEP file to STL File?
  • Can I Convert an STL File To a Step file?

What Is The Difference Between STL And STEP Files?

The most important difference between STL and STEP files is that STL files are used to print 3D models, while STEP files are used for data exchange and storage of more complex 3D models.

STL stands for “stereolithography” and is a file format specifically designed for creating 3D prints. This type of file is composed of triangles that make up the model, giving it its shape and surface details. STL files are easy to generate and can be quickly printed on a 3D printer with minimal effort.

STEP (Standard for Exchange of Product Model Data) is a file format used to store and transfer complex 3D models with many different features. It is a popular format for data exchange in many CAD and CAM systems, as it allows the user to share their designs with other parties. It is a much more detailed file format than STL, giving users more control over the 3D model’s features and properties.

In conclusion, STL files are used to create 3D prints while STEP files are used to exchange and store 3D models. STL files are composed of triangles while STEP files have a much more detailed structure, allowing users to control the design’s features in greater detail.

Here is a real-world example of the differences between these file types:

If I want to share CAD data with an external manufacturer so they can make the component I have modelled in CAD, or share CAD data with a client so they can explore and edit my CAD file, I will use STEP files.

Because this CAD file type has so much more data, a manufacturer such as a plastic injection moulding specialist can use this CAD file to explore the data and create precision parts from it.

On the other hand, if I want to share CAD data so it can be 3D printed I will send STL files, as this is perfect for 3D printers and the file size is not very large.


I have often heard new engineers ask if an STL and STEP file is the same thing.

No, an STL file is not a STEP file.

A Step (Standard for the Exchange of Product Data) file is a type of 3D CAD model format that is widely used in mechanical engineering and product design. It is a 3D model exchange format that offers complete interoperability between different CAD systems.

The primary purpose of STEP files is to capture the engineering intent of a 3D model, enabling precise data exchange and interoperability.

An STL (Stereolithography) file is also a type of 3D CAD model format, but it is primarily used for rapid prototyping and 3D printing applications.

It was designed to simplify the process of translating a design from a 3D CAD system into data for the physical production of a 3D object. While it does capture the shape and size of an object, its main purpose is to allow easy communication between CAD software and the physical manufacturing process.

The major differences between STEP files and STL files are their purposes—STEP files are used for exchanging detailed engineering information, while STL files are used for rapid prototyping and 3D printing.

Another key difference between the two formats is the level of detail captured in each file—STEP files capture more detailed engineering information than STL files.

Additionally, STEP files are often much larger than STL files due to their higher level of detail and complexity.

Lastly, while STEP files can be converted into STL files, the reverse is not true. This is because much of the detailed engineering information contained in a STEP file cannot be fully captured within an STL file.

Can A 3D Printer Read STEP Files?

A 3D printer cannot read STEP files. This is because 3D printers typically use STL files as their input format.

The main purpose of STEP files is to capture the engineering intent of a 3D model, which includes full details such as exact dimensions and materials used, while STL files are much simpler in nature and only capture the shape and size of an object.

As such, 3D printers are unable to interpret the engineering intent captured in STEP files.

However, it is possible to convert a STEP file into an STL file for use with a 3D printer. Most professional CAD packages can convert STEP files into STL files. Often it is simply a matter of opening your STEP file and exporting the file in STL.

Overall, while STEP files and STL files are both types of 3D CAD models, they are designed for different purposes—STEP files capture detailed engineering information, while STL files are used primarily for rapid prototyping and 3D printing applications.

As such, it is not possible for a 3D printer to read STEP files directly and the files need to be converted into an STL file before they can be printed.

What Is A STEP File Used For?

A STEP file is an acronym for Standard for the Exchange of Product Model Data, and it is a standard file format used in CAD (Computer Aided Design) programs for representing 3D objects.

This file type is very useful for exchanging information between different CAD programs, such as Autodesk and SolidWorks.

It allows users to easily move a model between programs without losing accuracy or detail.

The STEP file also allows for complex 3D objects to be broken down into basic components and then put back together in a new CAD program.

Whenever I have to share CAD data with an external client or manufacturer, I will use STEP files as they are widely recognised and open well in all CAD packages from SolidWorks to Siemens NX.

What Is An STL File Used For?

STL files are a type of 3D printing file, which represent the surface of a 3D object as a series of triangles.

This is a very common file format for 3D printing, as it is easy to read and contains all the data needed to accurately recreate the model in physical form.

The STL file can be used with most 3D printing software programs, including MakerBot, Cura or Simplify3D.

When To Use A STEP Or STL File?

If you are confused about when to use a STEP or STL file, the following table will help narrow your options.

This Table Compares STEP And STL Files

Can I Convert A STEP File To an STL File?

Most CAD packages can convert STEP files to STL files for 3D printing.

  1. Import your STEP file into your CAD package.
  2. Export your CAD as an STL file.

Can I Convert An STL File To a Step File?

No, it is not possible to convert an STL file to a STEP file. This is because an STL file contains very little internal geometric data, and does not have the data to create a comprehensive STEP file.

You may find some methods online which tell you that they can convert STL to STEP, and although the file extension may lead you to believe that you have a STEP file when you actually examine the file you will see that you have little more than an STL file.

Final Thoughts

In conclusion, STEP and STL files are both types of CAD models used for different purposes.

While a 3D printer cannot read STEP files directly, it is possible to convert them into an STL file in order to be printed.

The main purpose of the STEP format is to exchange detailed engineering information while the primary use of an STL file is for rapid prototyping and 3D printing applications.

When deciding which type of file you need for your project, consider its complexity and level of detail required as well as what program or device needs access to that data.

By understanding the differences between these two formats, you can ensure that your projects run smoothly with no unexpected roadblocks along the way.

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