How Do You Bend a 90 Degree Stub-Up?
The stub-up is the first bend every apprentice learns: a single 90 that turns a run up a wall or out of a slab. The only trick is that the bend itself eats into your measurement, so the mark does not sit at the finished height. Account for that with the deduct and the stub lands exactly where the print wants it.
How do you mark a 90 degree stub-up?
Measure the finished stub height the print calls for, subtract your bender's deduct, and mark the conduit at that point. For a 12 inch stub with a 3/4 inch bender, mark at 6 inches because the deduct is 6. Place the bender's arrow on that mark, not the end of the conduit, and the bend will rise to the full 12 inches.
The deduct exists because the conduit curves through the radius of the bend rather than turning a sharp corner. That curve consumes length between the mark and the finished back of the stub. Subtracting the deduct moves your mark back by exactly the amount the curve will use, so the stub stands at the height you measured for.
What is the deduct for a stub-up?
The deduct, also called take-up, is the distance from the back of the 90 to the bender arrow. It is set by the bender's radius: about 5 inches for 1/2 inch EMT, 6 inches for 3/4 inch, 8 inches for 1 inch, and 11.5 inches for 1.25 inch. Read the figure stamped on your shoe, since it varies slightly by manufacturer.
| Conduit size | Typical deduct |
|---|---|
| 1/2 inch EMT | 5 in |
| 3/4 inch EMT | 6 in |
| 1 inch EMT | 8 in |
| 1.25 inch EMT | 11.5 in |
These are standard hand-bender values. Large-radius shoes and IMC or rigid benders change them, so confirm against your tool before the first pull. The deduct stays constant regardless of how tall the stub is, because it depends only on the radius of the bend.
How do you pull a clean 90?
Set the conduit flat on the floor with the arrow on your mark, plant your foot on the bender's foot pedal, and pull the handle with steady pressure while pressing down through your heel. Bend until the conduit reaches the 90 degree mark on the bender. Keep weight on the shoe the whole way so the conduit hugs the radius and does not kink.
Stop short of 90 and the stub leans in; overbend and it leans out. Check the finished leg with a level. If it springs back a degree or two, a slight overbend compensates. Even foot pressure prevents a kink or a flattened spot at the heel of the bend, which weakens the conduit and looks rough on the rack.
Why is my stub-up the wrong height?
A stub that lands short or tall usually means the wrong deduct, an under or over bend past a true 90, or measuring from the wrong end of the conduit. Confirm the deduct stamped on your shoe, verify the bend is a full 90 with a level, and always measure the stub height to the back of the bend, not the inside.
Another quiet error is springback, where the conduit relaxes a degree or two after you release the handle. On EMT it is small; on heavier conduit it adds up. Bending a hair past 90 cancels it. Measure the same way every time, to the back of the stub, and your heights stay consistent across a whole rack of pipes.
Key takeaways
- Mark the conduit at the finished stub height minus the bender's deduct.
- Place the arrow on the mark, not on the end of the conduit.
- Typical EMT deducts are 5, 6, 8 and 11.5 inches by size.
- Pull a full 90 with steady foot pressure so the conduit hugs the shoe.
- Measure stub height to the back of the bend and account for springback.
Frequently asked questions
- Do I measure the stub to the inside or outside of the bend?
- Measure to the back of the bend, the outside of the stub, and keep that reference consistent for every pipe. The deduct values are figured to the back of the 90, so measuring there matches the chart. Switching between inside and outside mid-job is a common reason a rack of stubs comes out at inconsistent heights.
- Why does the arrow go on the mark instead of the end?
- The arrow marks where the bend's radius begins relative to the finished stub. Lining the arrow up with your mark, which already accounts for the deduct, places the curve so the back of the stub reaches your target height. Putting the end of the conduit on the mark ignores the deduct and the stub comes out short.
- Does the deduct change for a taller stub?
- No. The deduct depends on the bender's radius, not the height of the stub, so you subtract the same number whether the stub is 6 inches or 4 feet. Only changing bender size or conduit type changes the deduct. Tall stubs still use the same simple subtraction to find the mark.
- How do I keep a 90 from kinking?
- Keep steady downward pressure on the bender's foot pedal through the entire pull so the conduit stays seated against the shoe. A kink or flat spot at the heel happens when the conduit lifts off the radius partway through. Pulling smoothly with your foot driving the heel down keeps the bend round and the wall from collapsing.
Conduit Bending & NEC Reference, BigBalli. We turn the formulas in Benfield and Ugly's Electrical References into quick, checkable field math.
BendMarks is a teaching and estimation tool, not a substitute for licensed professional judgment or the National Electrical Code. Verify deducts against your bender and bends against the job's specifications.