Math

Instant, private, and free

Triangle Scale Factor Calculator.

Calculate the scale factor between corresponding triangle sides.

On-device calculationNo signup
01

Set your values

Results update as you type.

Scale factor: 1.5

Scale factor

0.000000
originalSide: 4

originalSide

0.000000
imageSide: 6

imageSide

0.000000
Percent change: 50

Percent change

0.000000

Results update automatically as you type.

Use Cases

Check similarity of triangles

Use the scale factor to verify if two triangles are similar by comparing corresponding side ratios. If the scale factor is the same for all sides, the triangles are similar.

Example: Original side 4, image side 8 gives scale factor 2.

Resize shapes in design or modeling

When scaling a triangle in graphic design, architecture, or 3D modeling, this calculator helps you determine the exact scaling ratio between the original and resized versions.

Example: Original side 10 cm, image side 15 cm gives scale factor 1.5.

Frequently Asked Questions

What is a triangle scale factor?
A triangle scale factor is the ratio of the lengths of corresponding sides of two similar triangles. It tells you how much the original triangle has been enlarged or reduced to create the image triangle. For example, a scale factor of 2 means the image is twice as large.
How do I use this calculator?
Enter the length of a side from the original triangle in the 'Original side' field and the corresponding side length from the image triangle in the 'Image side' field. The calculator will divide the image side by the original side to give you the scale factor.
What if the scale factor is less than 1?
If the scale factor is less than 1, the image triangle is smaller than the original. For example, a scale factor of 0.5 means the image is half the size. This calculator handles both enlargements and reductions.

Tips & Common Mistakes

Tips

  • Ensure you enter corresponding sides: the original side and the image side must refer to the same side of the triangle (e.g., both bases or both left sides).
  • The scale factor is unitless; it works with any unit (cm, inches, etc.) as long as both inputs use the same unit.
  • For a quick check, if the image side is larger than the original, the scale factor will be greater than 1; if smaller, it will be less than 1.
  • Use the scale factor to find missing side lengths: multiply the original side by the scale factor to get the image side.

Common Mistakes to Avoid

  • Mixing up original and image sides: the scale factor is image side divided by original side, not the reverse.
  • Using different units for the two sides (e.g., cm and inches) without converting, which leads to an incorrect scale factor.
  • Assuming the scale factor is always a whole number; it can be a decimal or fraction, especially when the image is not an exact multiple.

Last updated: August 13, 2026