Conduit Shrink Calculator
Shrink is the reduction in overall conduit length caused by an offset bend. When conduit travels at an angle between two bends instead of running straight, the finished piece ends up shorter than the original straight distance. Failing to account for shrink is one of the most common reasons conduit comes up short on the job.
This calculator focuses on shrink values. Enter your offset height and bend angle, and it returns the total shrink, shrink per inch of offset, and the travel distance between marks.
Shrink Formula
Total Shrink = Offset Height × Shrink Per Inch
Shrink per inch depends on the bend angle
Each bend angle has a fixed shrink-per-inch constant. The table below lists the values used by electricians in the field:
| Bend Angle | Shrink Per Inch | Example (6" Offset) |
|---|---|---|
| 10° | 1/16" | 3/8" |
| 22.5° | 3/16" | 1-1/8" |
| 30° | 1/4" | 1-1/2" |
| 45° | 3/8" | 2-1/4" |
| 60° | 1/2" | 3" |
How to Use This Calculator
- Enter the offset height — the perpendicular distance between the two parallel conduit runs. You can use inches, feet-inches, or fractions.
- Select the bend angle — 30° is the most common choice. Higher angles produce more shrink.
- Read the results — Total Shrink is the amount to add to your measurement. Shrink Per Inch is the constant for that angle. Travel is the distance between your bend marks.
When cutting conduit, add the total shrink to the distance from the last coupling or connector to the point where the offset starts. This compensates for the length lost in the bends.
Frequently Asked Questions
What is conduit shrink?
Conduit shrink is the reduction in overall end-to-end length that occurs when you make an offset bend. Because the conduit travels at an angle between the two bends instead of running straight, the finished piece is shorter than a straight run covering the same distance. You need to add the shrink value to your measurements so the conduit ends up at the correct length after bending.
How much does conduit shrink per inch of offset?
The shrink per inch of offset depends on the bend angle. At 10 degrees it is 1/16 inch per inch of offset. At 22.5 degrees it is 3/16 inch. At 30 degrees it is 1/4 inch. At 45 degrees it is 3/8 inch. At 60 degrees it is 1/2 inch. The higher the bend angle, the more shrink per inch of offset.
How do you account for shrink when cutting conduit?
To account for shrink, add the total shrink value to the measurement where you want the conduit to end up after bending. For example, if you need the conduit to land exactly 48 inches from a box and you have 1-1/2 inches of shrink, mark and cut at 49-1/2 inches. This ensures the offset does not pull the conduit short of its destination.