There isn't one single formula for calculating the outside diameter (OD). The formula depends on the shape of the object you're measuring. Here are some common scenarios:

1. Circles and Cylinders:

* OD = 2 * radius

* Where "radius" is the distance from the center of the circle to the edge.

* OD = diameter

* Where "diameter" is the distance across the circle through the center.

2. Regular Polygons:

* OD = (side length) / (sin(180/number of sides))

* Where "side length" is the length of one side of the polygon.

3. Other Shapes:

* For irregular shapes, you might need to use specific formulas based on the shape's geometry.

* For complex shapes, you might need to measure the OD directly using calipers or a ruler.

Example:

Let's say you have a circular pipe with a radius of 5 cm. Using the formula:

* OD = 2 * radius

* OD = 2 * 5 cm

* OD = 10 cm

Important Considerations:

* Make sure you are measuring the *outside* diameter, not the inside diameter (ID).

* Consider the units of measurement. The OD will be in the same units as the radius or diameter you used in the calculation.

Let me know if you have a specific shape in mind and I can help you find the appropriate formula.