When using AutoCAD, the scale factor is essential to ensure that a drawing fits on a given sheet size, or to adjust the size of an imported object to match the scale of the current drawing. Scale factor is the command used to adjust the size of objects or drawings.
In this article we’ll look at how to determine the scale factor and how to change the scale factor of objects to the size you want.
Formula for Scaling
Scale Factor=Desired Size/Original Size
Explanation
- Original Size: This is the current size of the object or dimension in your drawing. It can be a length, width, height, or any measurable attribute of the object.
- Desired Size: This is the size you want the object or dimension to be after scaling.
- Scale Factor: This is the numerical value that you will use to scale the object in AutoCAD.
- If the scale factor is greater than 1, the object will increase in size.
- If the scale factor is less than 1 (but greater than 0), the object will decrease in size.
- If the scale factor is exactly 1, the object will remain its original size, of course. Ideally, your files should be on a 1:1 reference scale. Its industry standard and much easier for anyone who has to work with your files.
Example
Suppose you have a line that is 50 units long (Original Size), and you want it to be 100 units long (Desired Size). The scale factor would be calculated as follows:
scale factor = 100 units (desired size) 50 units (original size) = 2
So, you would use a scale factor of 2 to scale the line to your desired length in AutoCAD.
This formula applies to uniform scaling where all dimensions (length, width, height) of an object are scaled by the same factor. For non-uniform scaling (different scale factors for different dimensions), you would apply this formula independently for each dimension.
Steps to Use Scale Factor in AutoCAD
Step 1: Select the Object(s) to Scale
Click on the object or multiple objects you intend to scale. For multiple selections, hold the “Shift” key while clicking each object.
Step 2: Accessing the Scale Command
The scale command can be accessed either by typing SCALE in the command line and pressing Enter, or by locating the Scale tool in the Modify panel on the Home tab.
Step 3: Specify the Base Point
After activating the scale command, specify a base point. This serves as a pivot point for scaling. Select a point on the drawing to set this base point.
Step 4: Entering the Scale Factor
Next enter the scale factor. For example, a scale factor of 2 will double the size of the object, while 0.5 will halve it. Enter the scale factor from the command line or visually scale the object with the mouse and click to finalise the new size.
Step 5: Review and Adjust if Necessary
Check the scaled object(s). If the scaling isn’t satisfactory, press (CTRL + Z) and repeat the process using a different factor.
This article explains the basic operation of AutoCAD.
Tips for Effective Scaling
- Understand Units: Grasping the units in your drawing aids in determining the correct scale factor.
- Use Reference Objects: Employ a known-sized reference object for uncertain scale factors.
- Keep Proportions: The scale command normally maintains object proportions. Use the stretch command for proportion alterations.
Charts for reference:
Architectural Scales
DRAWING SCALE | SCALE FACTOR | Viewport
Scale |
Decimal
Scale |
1/16″ = 1′-0″ | 192 | 1/192xp | .0625″ = 1′-0″ |
3/32″ = 1′-0″ | 128 | 1/128xp | .09375″ = 1′-0″ |
1/8″ = 1′-0″ | 96 | 1/96xp | .125″ = 1′-0″ |
3/16″ = 1′-0″ | 64 | 1/64xp | .1875″ = 1′-0″ |
1/4″ = 1′-0″ | 48 | 1/48xp | .25″ = 1′-0″ |
3/8″ = 1′-0″ | 32 | 1/32xp | .375″ = 1′-0″ |
1/2″ = 1′-0″ | 24 | 1/24xp | .50″ = 1′-0″ |
3/4″ = 1′-0″ | 16 | 1/16xp | .75″ = 1′-0″ |
1″ = 1′-0″ | 12 | 1/12xp | 1″ = 1′-0″ |
1 1/2″ = 1′-0″ | 8 | 1/8xp | 1.5″ = 1′-0″ |
3″ = 1′-0″ | 4 | 1/4xp | 3″ = 1′-0″ |
Engineering Scales
DRAWING SCALE | SCALE FACTOR | VIEWPORT SCALE |
1″ = 10′-0″ | 120 | 1/120xp |
1″ = 20′-0″ | 240 | 1/240xp |
1″ = 30′-0″ | 360 | 1/360xp |
1″ = 40′-0″ | 480 | 1/480xp |
1″ = 50′-0″ | 600 | 1/600xp |
1″= 60′-0″ | 720 | 1/720xp |
1″ = 70′-0″ | 840 | 1/840xp |
1″ = 80′-0″ | 960 | 1/960xp |
1″ = 90′-0″ | 1080 | 1/1080xp |
1″ = 100′-0″ | 1200 | 1/1200xp |
Common Issues and Troubleshooting
- Objects Disappear: Extreme scale factors can cause objects to vanish or overly enlarge. Undo and retry with a moderate factor.
- Non-Uniform Scaling: For scaling in varied directions, utilize the non-uniform scaling option.
Scaling an Object to Match Another Using Reference Points
Step 1: Select the Object to Scale
Activate the SCALE command by typing SCALE at the command prompt and pressing Enter. Then select the object to be scaled.
Step 2: Specify the Base Point
Select a fixed base point on your object for scaling, ideally aligned with a specific part of the target object.
Step 3: Select the First Reference Point
Select a reference point on your object that will act as the first point of the scale line.
Step 4: Select the Second Reference Point
Select the second reference point on your object to determine the original length for AutoCAD’s scaling calculation.
Step 5: Specify the New Length
Type the new length directly or click on the target object to set the length.
Step 6: Verify the Scaling
Use the MEASUREGEOM command to confirm that the size of the scaled object matches the intended dimension.
Example: To scale a rectangle (object A) to fit another (object B), follow the steps of selecting, specifying base points and setting the new length according to the dimensions of object B.
Tips for Scaling
- Alignment Matters: Select reference points that align easily with the target object.
- Use Object Snaps: This assists in selecting precise points on objects.
This two-point pivot scaling method allows objects to be scaled intuitively without the need for manual scale factor calculations.
Common Mistakes and How to Avoid Them in AutoCAD Scaling
Understanding these common mistakes and knowing how to avoid them can save time and improve the accuracy of your drawings:
This article explains AutoCAD scaling in detail.
Incorrect Unit Conversion:
- Mistake: A common mistake is not converting units correctly, resulting in a mismatch between intended and actual sizes.
- Avoidance: Always check the unit settings in both your current drawing and any imported elements. Ensure that unit types (e.g. millimetres, inches) are consistent across all elements in your drawing.
Misinterpreting Scale Factors:
- Mistake: Misunderstanding how scale factors work, e.g. assuming that a scale factor of 2 halves the size instead of doubling it.
- Avoidance: Remember that a scale factor greater than 1 increases size, while a factor less than 1 but greater than 0 decreases it. Test the scale factor on a non-critical object first if unsure.
Scaling Objects Individually Instead of as a Group:
- Mistake: Scaling objects individually can lead to misalignment and inconsistency, especially in complex drawings.
- Avoidance: If necessary, select and scale multiple objects as a group. This preserves their relative positions and proportions.
Ignoring Annotation Scale:
- Mistake: Forgetting to adjust the scale of annotations, texts, and dimensions, which can become unreadable after scaling.
- Avoidance: Use the annotation scale feature to ensure that texts and dimensions are automatically adjusted to suit the scale of the viewport.
Neglecting Reference Points:
- Mistake: Choosing an inappropriate reference point can lead to objects being scaled in an unintended way.
- Avoidance: Select a reference point that makes sense for the desired scaling transformation. The reference point acts as a pivot point around which the object scales.
Overlooking Block Attributes:
- Mistake: Scaling blocks without considering the scaling of block attributes, resulting in disproportionate or misaligned attributes.
- Avoidance: Enable the Uniform Scale option when scaling blocks and use the ATTSYNC command after scaling to adjust attributes if necessary.
Improper Use of Non-Uniform Scaling:
- Mistake: Applying non-uniform scaling without considering the impact on the object’s proportions and interrelationships.
- Avoidance: Use non-uniform scaling with care, especially when dealing with mechanical parts or architectural elements where maintaining proportion is critical.
Advanced Scale Factor Tips
Custom Scale Factors for Annotations and Text:
- When dealing with annotations, text, and dimensions, consider setting a different scale factor to maintain legibility. AutoCAD allows you to apply a separate scale for these elements which can be adjusted independently from the main drawing scale.
Automating Scaling with Scripts and LISP Routines:
- For repetitive scaling tasks, consider automating the process using AutoCAD’s scripting capabilities or LISP routines. This can save time and reduce errors in large projects.
- Create custom scripts to handle routine scaling operations, especially when working with standardised drawing formats or repetitive design elements.
Non-Uniform Scaling for Design Flexibility:
- Explore uneven scaling for creative design needs. This technique allows you to scale objects differently in the X, Y and Z directions, giving you greater control over complex shapes and designs.
- This can be particularly useful in architectural or mechanical designs where asymmetrical scaling is required.
Integration with External Data and Models:
- When importing data or models from other software, use the scale factor to align the imported elements with the scale of your current drawing. This is essential for maintaining accuracy in mixed software environments.
- Check for unit discrepancies when importing and use scaling to correct any discrepancies.
Experimenting with Dynamic Blocks for Scalable Designs:
- Utilise dynamic blocks which can be scaled without losing their proportions or functionalities. This can be particularly useful for components that need to be used at various sizes within the same project.
Scale Factor in 3D Modeling:
- When 3D modelling in AutoCAD, understanding and applying scale factors can be critical for rendering and 3D printing. Ensure that the scale in your virtual model matches the real-world dimensions required for production.
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Conclusion
In conclusion, mastering the use of the AutoCAD scale factor is an invaluable skill for any designer or engineer. This article has provided a comprehensive guide to calculating and setting the scale factor in AutoCAD, ensuring precision and efficiency in your work.
We explored the basic formula for scaling, which is the ratio of the desired size to the original size, and detailed the steps for applying this formula in AutoCAD. From selecting the objects to scaling, specifying the base points and entering the scale factor, each step is critical to accurate scaling.
Whether you’re working on a small component or a large architectural plan, the ability to correctly scale objects is key to creating drawings that are accurate and visually consistent with real-world dimensions.
Remember, practice and patience are essential to your AutoCAD journey. By honing these skills, you’ll ensure that your designs are not only accurate, but also practical and compliant with industry standards.