Gain and Deduct Calculator
Key Takeaways
- Deduct is subtracted from the stub height to find your mark position
- Gain is the extra conduit length from bending vs. a sharp corner
- Both values depend on the bender radius for your conduit type and size
Contents
What Are Gain and Deduct?
When making a 90-degree bend in conduit, two key values determine the accuracy of your bend: the deduct and the gain. The deduct is the distance you subtract from your desired stub height to find where to place your mark on the conduit. The gain is the extra length of conduit created by the arc of the bend compared to what you would need if the conduit made a perfect sharp right-angle corner.
Mark = Stub Height - Deduct
Deduct values are determined by the bender manufacturer and depend on the bending radius. Different conduit types and sizes require different bender shoes with different radii, so each combination has its own deduct and gain values.
EMT Deduct and Gain Reference Table
The following table lists the standard deduct and gain values for EMT conduit across all common sizes:
| EMT Size | Radius | Deduct | Gain |
|---|---|---|---|
| 1/2" | 4" | 5" | 3.125" |
| 3/4" | 4.5" | 6" | 3.375" |
| 1" | 5.75" | 8" | 3.5" |
| 1-1/4" | 7.25" | 11" | 2.625" |
| 1-1/2" | 8.25" | 13" | 1.875" |
How to Use Deduct
To make an accurate 90-degree stub-up, follow these steps:
- Determine your desired stub height (the distance from the floor to the top of the conduit)
- Look up the deduct value for your conduit type and size
- Subtract the deduct from the stub height
- Make your mark at that distance from the end of the conduit
- Align the mark with the bender's arrow and make the bend
Example: 12" Stub with 1/2" EMT
- Stub height: 12 inches
- Deduct (1/2" EMT): 5 inches
- Mark position: 12 - 5 = 7 inches from end
- Gain: 3.125 inches saved over a sharp corner
Frequently Asked Questions
What is deduct in conduit bending?
Deduct is the amount you subtract from the desired stub height to determine where to place your mark on the conduit before making a 90-degree bend. For example, with 1/2-inch EMT and a deduct of 5 inches, a 12-inch stub requires marking at 7 inches from the end.
What is gain in conduit bending?
Gain is the extra length of conduit you get when making a 90-degree bend compared to two straight pieces meeting at a right angle. It occurs because the bend follows an arc rather than a sharp corner. Gain is calculated as (2 x radius) minus the deduct.
Why does conduit size affect the deduct value?
Larger conduit sizes require benders with larger bending radii to prevent the conduit from kinking or collapsing. A larger radius means a wider arc through the bend, which changes the geometric relationship between the stub height and the mark position, resulting in a different deduct value.