90-Degree Bend & Back-to-Back 90s: Complete Conduit Guide

The 90-degree bend is the first bend every apprentice learns, and the one journeymen use more than any other. Whether you're stubbing up into a panel, turning a corner in a ceiling grid, or running EMT conduit down a wall, the 90 is the foundation. Get this one wrong and everything downstream goes crooked.

This guide covers two bends: the basic 90-degree stub-up and the back-to-back 90 (two 90s on the same stick of conduit). You'll learn the deduct method, the gain formula, how to measure for back-to-back bends, and the mistakes that catch people on the job site. If you're looking for a broader overview of every bend type, start with our beginner's guide to bending conduit.

The 90-Degree Stub-Up: How It Works

A stub-up is the simplest form of a 90-degree conduit bend. The conduit runs horizontally along the floor or a surface, then turns straight up. You see it everywhere: conduit entering junction boxes mounted on a wall, pipes stubbing into panels, runs turning up from a slab.

The key concept is deduct (also called take-up). When you bend conduit, the bender's shoe has a radius. That radius means part of the conduit "goes into" the curve before reaching 90 degrees. The deduct value tells you how much to subtract from the desired stub height so your mark aligns to the bender's arrow and produces the correct final height.

Deduct Values by Conduit Size

Standard deduct (take-up) values for EMT hand benders. These values apply to most major bender brands (Ideal, Klein, Greenlee).

Conduit Size	Deduct (Take-Up)	Stub-Up Formula
1/2" EMT	5"	Mark = Stub Height - 5"
3/4" EMT	6"	Mark = Stub Height - 6"
1" EMT	8"	Mark = Stub Height - 8"
1-1/4" EMT	11"	Mark = Stub Height - 11"

These deduct values come from the bender manufacturer and are typically stamped right on the bender shoe. If your bender's markings have worn off, check the manufacturer's specs or simply bend a test piece and measure the result. For a full chart of deduct values alongside multipliers and shrink constants, see our conduit bending formulas reference.

Step-by-Step: Bending a 90-Degree Stub-Up

Here's the process using 1/2" EMT as the example. The same steps apply to 3/4" and 1" with different deduct values.

Step 1: Determine the Stub Height

Measure from the mounting surface (floor, strut, bracket) to the point where the conduit needs to reach. Say you need the conduit to stub up 12 inches into a junction box.

Step 2: Subtract the Deduct

For 1/2" EMT, the deduct is 5 inches.

12" - 5" = 7"

Step 3: Mark the Conduit

From the end of the conduit that will become the stub (the short vertical leg), measure 7 inches and make a clear pencil mark all the way around the pipe. As noted in EC&M's bending tips, always girdle the conduit 360 degrees with your pencil mark so it stays visible while you work the bender.

Step 4: Align the Mark to the Arrow

Slide the conduit into the bender shoe with the pencil mark lined up to the arrow (the take-up mark). The end of the conduit that will become the stub should be pointing away from the bender handle.

Step 5: Bend to 90 Degrees

Place the bender on the floor with the hook cradling the conduit. Keep constant foot pressure on the pedal while pulling the handle steadily toward you. Don't jerk. Smooth, even pressure prevents kinks and dog-legs. According to EC&M, all 90-degree bends should be made on the floor whenever possible for the best leverage and accuracy.

Step 6: Check with a Level

Stand the conduit up on the horizontal leg. Place a torpedo level on the stub. If it reads exactly plumb, you're at 90 degrees. If it's leaning back slightly, that's spring-back. Put the conduit back in the bender and apply a bit more pressure to push past 90 by a degree or two. EMT naturally springs back about 2 to 3 degrees.

Step 7: Verify the Stub Height

Measure from the floor (or the surface the horizontal leg sits on) to the end of the stub. It should read 12 inches. If it's off by more than 1/8", re-check your deduct value and your mark placement.

Worked Example: 3/4" EMT, 18" Stub-Up

Target stub height: 18 inches

Conduit: 3/4" EMT

Deduct for 3/4": 6 inches

1. 18" - 6" = 12". That's your mark distance from the stub end.
2. Mark the conduit at 12" from the end.
3. Align the mark to the bender arrow.
4. Bend to 90 degrees on the floor.
5. Verify: the stub should measure 18" from the back of the bend to the end of the pipe.

Need to run the numbers faster? Plug in any stub height on the 90-Degree Bend Calculator and it'll give you the mark, gain, and developed length instantly.

Understanding Gain

When conduit bends through a 90-degree arc, it follows a curve instead of making a sharp right-angle corner. Because the curved path is shorter than the sum of two straight legs meeting at a corner, the conduit "gains" length. This is called gain.

Gain matters when you're cutting conduit to length before bending. If you measure the total run (horizontal + vertical) and cut the pipe to that exact length, the finished piece will be too long by the gain amount. You need to subtract the gain from your total cut length.

Gain Formula

For a 90-degree bend:

Gain = (2 x Radius) - (pi/2 x Radius)

Simplified: Gain = Radius x (2 - 1.5708) = Radius x 0.4292

In practice, you don't need to calculate this every time. The gain values are fixed for each conduit size because the bender radius is fixed.

Gain Values by Conduit Size

90-degree gain values for EMT conduit using standard hand benders.

Conduit Size	Bender Radius	Gain (90-Degree Bend)
1/2" EMT	4"	3"
3/4" EMT	4-1/2"	3-7/8"
1" EMT	5-3/4"	5-1/4"
1-1/4" EMT	7-1/4"	6-1/4"

For a deeper dive into gain, deduct, and how they relate to each other, see our Gain & Deduct Calculator or the full bending formulas reference.

Back-to-Back 90-Degree Bends

A back-to-back 90 puts two 90-degree bends on the same piece of conduit, forming a U-shape or Z-shape. It's how you get conduit up a wall, across a ceiling, and back down the other side. Or up out of a trench, across a gap, and back into the trench. Anywhere you need two direction changes on one stick of pipe.

The key difference from a single stub-up: for the second bend, you don't use the arrow. You use the star (or rim notch) on the bender shoe. The star marks the back of the bend, which is the reference point for measuring between two 90s.

How to Measure for Back-to-Back 90s

You need one measurement: the distance between the backs of the two bends. The "back" of a 90-degree bend is the outermost point of the curve, where the conduit changes direction.

1. Bend the first 90 as a normal stub-up using the deduct method described above.
2. Measure the back-to-back distance. This is the straight-line distance between the two direction-change points. For example, if conduit needs to go up 24 inches, travel 36 inches across a ceiling, and come back down, the back-to-back distance is 36 inches (the horizontal run across the top).
3. Mark from the back of the first bend. With the first 90 already bent, find the back of that bend (the apex of the curve). Measure 36 inches from that point along the straight conduit and make your mark.
4. Align the mark to the star. Place the conduit in the bender with the pencil mark aligned to the star (rim notch), not the arrow. The first bend should be on the opposite side from where the handle pushes.
5. Bend the second 90. Make sure the second bend goes in the same plane as the first. If the first bend curves up, the second should also curve up (creating a U) or in the appropriate direction for your installation.

Run the numbers with the Back-to-Back 90 Calculator to get exact mark placement before you pick up the bender.

Worked Example: Back-to-Back 90, 1/2" EMT

Scenario: Conduit runs from a panel stub (12" stub-up), travels 30 inches horizontally along the ceiling, then drops back down to another box.

First Bend (Stub-Up)

1. Stub height: 12"
2. Deduct for 1/2" EMT: 5"
3. Mark: 12" - 5" = 7" from the end
4. Align mark to arrow, bend to 90 degrees

Second Bend (Back-to-Back)

1. Back-to-back distance: 30" (the horizontal ceiling run)
2. Find the back of the first bend. Lay the conduit on the floor with the stub pointing up. The back is the point where the curve peaks.
3. From the back, measure 30" along the straight section and mark.
4. Place the conduit in the bender with the mark on the star.
5. Make sure the second bend goes in the correct direction (opposite to the first, creating the U-shape).
6. Bend to 90 degrees.

The finished piece should have a 12" stub on one end, a 30" horizontal run, and a second stub coming down. Measure to confirm both stubs are plumb and the horizontal measurement between bend backs is 30".

Keeping Back-to-Back 90s in Plane

The trickiest part of a back-to-back 90 is keeping both bends in the same plane. If the second bend rotates even a few degrees off axis, the conduit will twist and won't lay flat against the wall or ceiling.

• Use the floor as your reference. After the first bend, lay the conduit flat on the floor. The first bend should sit with both legs touching the floor. When you put the conduit in the bender for the second bend, make sure the first bend's plane stays parallel to the floor.
• Use anti-rotation marks. Before bending, draw a straight line along the top of the conduit with a pencil. After the first bend, that line should run in a continuous straight path. For the second bend, keep that pencil line in the same orientation.
• Check it before committing. After bending, lay the finished piece on the floor. Both stubs and the horizontal run should all be flat. If one stub lifts off the floor, you have a twist. On 1/2" EMT, you can sometimes hand-correct a small twist. On larger pipe, you may need to start over.

Cutting Conduit to Length: Accounting for Gain

When you're cutting conduit before bending (which is common when working from a material list or pre-fabricating), you need to account for gain on every 90-degree bend.

For a single 90:

Cut Length = Stub Height + Horizontal Run - Gain

For back-to-back 90s:

Cut Length = Stub 1 + Horizontal Run + Stub 2 - (2 x Gain)

Example: Cut Length for Back-to-Back 90s

Using 1/2" EMT with two 12" stubs and a 30" horizontal run:

• Total measured length: 12" + 30" + 12" = 54"
• Gain per 90: 3" (from the table above)
• Total gain for two 90s: 2 x 3" = 6"
• Cut length: 54" - 6" = 48"

Cut your stick at 48 inches and the finished piece will fit the 54-inch measured path exactly. For more on cut-length calculations, check the Conduit Cut Length Calculator.

Common Mistakes

These are the errors that cost apprentices (and some journeymen) time and conduit on the job site.

• Using the arrow for the second back-to-back bend. The arrow is for the first bend only. The second bend uses the star (rim notch) because you're measuring from the back of the existing bend. Using the arrow for both gives you the wrong distance between bends.
• Wrong deduct value. Deduct values vary by conduit size. Mixing up the 5" (1/2") and 6" (3/4") deducts throws off every bend by an inch. Always double-check which bender you're using before marking.
• Not compensating for spring-back. EMT springs back 2 to 3 degrees after bending. If you stop right at 90 on the bender, you'll end up at 87 or 88 degrees. Overbend slightly, then check with a level.
• Dog-legs from inconsistent pressure. A dog-leg happens when the conduit bends slightly to one side during the bend. It's usually caused by twisting the handle or not keeping foot pressure centered on the bender. The conduit ends up with a slight S-curve instead of a clean 90.
• Forgetting gain when cutting to length. If you measure the total run and cut without subtracting gain, the finished piece will be too long. On a back-to-back 90, you need to subtract gain twice (once for each bend).
• Twisting between bends. On back-to-back 90s, if you don't keep the conduit in the same plane for both bends, the piece will twist. This is the most common back-to-back error. Always mark a reference line on the conduit and use the floor to verify alignment before the second bend.
• Exceeding the 360-degree rule. Per NEC Section 358.26, the total bends between pull points can't exceed 360 degrees. A back-to-back 90 eats up 180 degrees of that budget in one shot. Plan your runs so you don't box yourself into a code violation. As EC&M explains, this restriction exists to keep conductor pulling tension within safe limits.

Tips from the Field

• Verify your bender's deduct. Bender manufacturers list standard values, but wear and brand differences can shift the actual deduct by a fraction. As Mike Holt's bending reference explains, always bend a test piece of scrap conduit, measure it, and confirm the deduct matches what you expect. Do this any time you pick up an unfamiliar bender.
• Use the developed length for pre-fab. When pre-fabricating multiple identical pieces (like ten stubs for a panel room), calculate the cut length once, cut all the pieces, then bend them on an assembly-line basis. This saves time and produces consistent results.
• Mark your bender handle at 90 degrees. When the bender handle reaches a certain angle relative to the floor, you're at 90 degrees. With most benders, this is when the handle is roughly perpendicular to the floor. Some benders have a built-in level bubble or degree indicator. If yours doesn't, stick a small torpedo level to the handle with a magnet.
• For parallel runs, account for conduit spacing. When bending back-to-back 90s on parallel conduits (like a rack going up a wall, across, and back down), the inner conduits need shorter back-to-back distances than the outer ones. The difference depends on the strap spacing. See our offset bend guide for parallel offset techniques.
• Use the Conduit Bending app in the field. Enter the stub height and conduit size, and the app returns the mark placement, gain, and developed length. It's faster than doing the mental math, especially when you're bending in tight spaces or under time pressure.

90-Degree Bend vs. Other Bend Types

Comparison of 90-degree bends to other common conduit bend types.

Bend Type	Purpose	Key Formula	Difficulty
90-Degree Stub-Up	Turn conduit from horizontal to vertical	Mark = Stub - Deduct	Beginner
Back-to-Back 90	Two direction changes on one stick	Star alignment, back-to-back distance	Beginner-Intermediate
Offset Bend	Move conduit parallel to itself	Travel = Offset x Multiplier	Intermediate
3-Point Saddle	Go over an obstruction	Shrink per inch x obstruction height	Intermediate
4-Point Saddle	Go over wide obstruction	Four matched bends, shrink + travel	Advanced
Rolling Offset	Move conduit in two planes at once	3D triangle: roll + rise + offset	Advanced

For a single reference page with all the formulas, multipliers, and shrink values you'll need on the job, see our conduit bending formulas cheat sheet.

How to Do This in Conduit Bending

The Conduit Bending app has dedicated calculators for both the single 90 and the back-to-back 90.

Single 90-Degree Bend

1. Open the app and select the 90-Degree Bend calculator.
2. Choose your conduit size (1/2", 3/4", 1", or 1-1/4").
3. Enter the stub-up height.
4. The app returns: mark placement, deduct used, gain, developed length, and a visual diagram of the bend.

Back-to-Back 90

1. Select the Back-to-Back 90 calculator.
2. Enter the first stub height and the back-to-back distance.
3. The app calculates both mark positions, the total cut length (with gain subtracted), and shows the finished profile.

You can also try these calculations for free with our online 90-Degree Bend Calculator and Back-to-Back 90 Calculator.

Quick Reference Table

Quick reference: deduct, gain, and example marks for common stub heights across EMT sizes.

Conduit	Deduct	Gain	6" Stub Mark	12" Stub Mark	18" Stub Mark	24" Stub Mark
1/2" EMT	5"	3"	1"	7"	13"	19"
3/4" EMT	6"	3-7/8"	N/A*	6"	12"	18"
1" EMT	8"	5-1/4"	N/A*	4"	10"	16"
1-1/4" EMT	11"	6-1/4"	N/A*	1"	7"	13"

*Stub heights below the deduct value are not possible with a standard hand bender because the mark would fall behind the bender shoe.

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Frequently Asked Questions

What is the deduct for a 90-degree bend?

The deduct depends on the conduit size: 5 inches for 1/2" EMT, 6 inches for 3/4" EMT, 8 inches for 1" EMT, and 11 inches for 1-1/4" EMT. To find your mark, subtract the deduct from the desired stub-up height and place your mark at that distance from the end of the conduit.

How do you measure for a back-to-back 90?

Measure the distance between the backs of the two 90-degree bends. After completing the first bend, find the back (apex) of that curve. Measure your back-to-back distance from that point along the conduit and make a mark. Then place the conduit in the bender with the mark on the star or rim notch, not the arrow.

What is gain in conduit bending?

Gain is the length of conduit saved because a bend follows an arc instead of making a sharp corner. For a 90-degree bend, the gain for 1/2" EMT is about 3 inches, for 3/4" EMT about 3-7/8 inches, and for 1" EMT about 5-1/4 inches. When cutting conduit to length before bending, subtract the gain for each 90-degree bend from the total measured distance.

Why is my 90-degree conduit bend too short?

The most common cause is using the wrong deduct value for your conduit size or bender brand. Check that you're using the correct deduct (5" for 1/2", 6" for 3/4", 8" for 1"). Another common cause is spring-back: EMT relaxes 2 to 3 degrees after you release pressure. Overbend slightly past 90 to compensate.

How many 90-degree bends are allowed between pull points?

Per NEC Section 358.26, the total bends between pull points cannot exceed 360 degrees. That equals four 90-degree bends. Any combination of bend angles is allowed as long as the total does not exceed 360 degrees. This limit prevents excessive pulling tension that could damage conductor insulation.