Calculate 3/4 EMT offset travel, rise, or bend angle from any two values, with optional shrink factor to estimate shrink allowance.
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3/4 EMT Offset (Travel) Formula
The calculator uses standard two-bend offset geometry. For a 3/4 EMT offset, the travel, also called bend spacing, is the distance between the two bend marks. The offset height is the rise needed to clear the obstacle.
- OL = offset length, bend spacing, or travel between the two bend marks
- OH = offset height or rise
- BA = bend angle of each bend
- S = shrink factor, in inches of shrink per inch of offset height
- sin = sine function, using the bend angle
- arcsin = inverse sine, used to solve for the bend angle
If you enter OH and BA, the calculator finds the bend spacing using OL = OH / sin(BA).
If you enter OL and BA, it finds the offset height using OH = OL * sin(BA).
If you enter OL and OH, it finds the bend angle using BA = arcsin(OH / OL). The offset height must be less than or equal to the travel for this calculation to be valid.
The shrink allowance is estimated from OH * S. If you do not enter a shrink factor, the calculator uses a common electrician table for standard angles, or a geometric estimate for other angles.
Common 3/4 EMT Offset Bend Angle Values
These values are useful when laying out common two-bend offsets. The travel multiplier is multiplied by the offset height to get the distance between bend marks.
| Bend angle | Travel multiplier | Formula use | Typical shrink factor |
|---|---|---|---|
| 10° | 5.7588 | OL = OH × 5.7588 | 1/16 in per inch of rise |
| 22.5° | 2.6131 | OL = OH × 2.6131 | 3/16 in per inch of rise |
| 30° | 2.0000 | OL = OH × 2 | 1/4 in per inch of rise |
| 45° | 1.4142 | OL = OH × 1.4142 | 3/8 in per inch of rise |
| 60° | 1.1547 | OL = OH × 1.1547 | 1/2 in per inch of rise |
Input Unit Reference
| Input | Accepted units | Notes |
|---|---|---|
| Bend spacing / travel | in, ft, m | Distance between the two bend marks. |
| Offset height / rise | in, ft, m | Vertical rise needed to clear the obstruction. |
| Bend angle | degrees, radians | Angle of each bend in the two-bend offset. |
| Shrink factor | ratio | Optional. Use a table value or enter your own job-specific value. |
Examples
Example 1: Find travel for a 6 inch offset using 30° bends
Given:
- OH = 6 in
- BA = 30°
The bend marks should be spaced 12 inches apart. Using the typical 30° shrink factor of 1/4, the shrink allowance is:
Example 2: Find bend angle from travel and offset height
Given:
- OL = 10 in
- OH = 5 in
Each bend should be 30°.
FAQ
What does travel mean in a 3/4 EMT offset?
Travel is the distance between the two bend marks for a two-bend offset. It is not the offset height. The offset height is the amount the conduit rises. Travel depends on both the rise and the bend angle.
Does the formula change because the conduit is 3/4 EMT?
The basic offset geometry does not change. The formula OL = OH / sin(BA) applies to the centerline layout of a two-bend offset. In practice, the exact finished result can be affected by the bender, bend radius, shoe marks, and how the conduit is seated in the bender.
What shrink factor should you use?
Use the shrink factor that matches your bend angle when possible. Common values are 1/4 for 30°, 3/8 for 45°, and 1/2 for 60°. If you have a known value for your bender or layout method, enter it directly instead of relying on a general table value.
