Conduit Bending Formulas & Deduct Charts: Quick Reference

Every conduit bending chart you'll find taped inside a gang box boils down to three things: deduct values, multipliers, and shrink constants. Memorize those numbers and you can handle any bend a foreman throws at you. Forget them and you'll waste conduit all day.

This conduit bending formulas reference puts every number you need in one place. Deductions for stub-ups, multipliers for offsets, shrink per inch for saddles, and gain values for cut-length calculations. Print it, bookmark it, or screenshot it for the job site. If you want to skip the math entirely, the Gain & Deduct Calculator and Bend Multiplier Calculator on conduitbending.com will do the arithmetic for you.

Deduct Values (Stub-Up Chart)

The deduct (also called "take-up") is the distance you subtract from your stub-up height before marking the conduit. It accounts for the arc of the bend. Every hand bender has its deduct stamped on the frame, but the standard values across all major bender brands are consistent.

Here's how it works: if you need a 10-inch stub-up with 1/2" EMT, subtract the 5-inch deduct. Mark the conduit at 5 inches from the end, align the bender arrow on that mark, and bend to 90 degrees. The result is a stub that measures exactly 10 inches.

Standard deduct values for EMT hand benders by conduit trade size

EMT Size	Deduct	Bender Radius	Min. Stub
1/2"	5"	4"	5"
3/4"	6"	4-1/2"	6"
1"	8"	5-3/4"	8"
1-1/4"	11"	7-1/4"	11"

These deducts apply to standard hand benders (Ideal, Klein, Gardner Bender, Greenlee). Mechanical and hydraulic benders for larger conduit (1-1/2" and above) use different shoes with different radii, so always check the bender documentation for those sizes. The EC&M bending guide covers the principles behind these values in detail.

Offset Multiplier Chart

Offset bends use two equal bends in opposite directions to move conduit around an obstacle. The multiplier tells you how far apart to space your two marks based on the offset height (the distance the conduit needs to move over).

The formula is simple:

Distance between marks = Offset height x Multiplier

These multipliers come from basic trigonometry. The multiplier is the cosecant of the bend angle (1 / sin(angle)). You don't need to know that on the job, but it explains why the numbers are what they are.

Offset bend multipliers, shrink per inch, and shrink constants by bend angle

Bend Angle	Multiplier	Shrink per Inch	Shrink Constant
10°	5.76	1/16"	0.0625
15°	3.86	1/8"	0.132
22.5°	2.61	3/16"	0.199
30°	2	1/4"	0.25
45°	1.41	3/8"	0.414
60°	1.15	1/2"	0.577

The three angles you'll use 90% of the time are 30, 45, and 60 degrees. Most electricians default to 30 degrees for offsets because the multiplier (2x) is the easiest to calculate in your head and the bend produces less stress on the conduit than steeper angles.

Need these values calculated instantly? The Bend Multiplier Calculator gives you the multiplier, shrink per inch, and shrink constant for any angle.

Shrink: What It Is and How to Account for It

When you put an offset in conduit, the overall length of the conduit gets shorter. That's shrink. If you don't account for it, your conduit will come up short and the far end won't land where it needs to.

The formula:

Shrink = Offset height x Shrink constant

For a 6-inch offset at 30 degrees:

• Shrink = 6" x 0.25 = 1.5"
• Add 1.5" to your first mark distance from the end of the conduit

For the same 6-inch offset at 45 degrees:

• Shrink = 6" x 0.414 = 2.48" (roughly 2-1/2")

This is why 30-degree offsets are popular on the job. Less shrink means a simpler layout. The Conduit Shrink Calculator handles these calculations for any angle and offset distance.

Gain and Deduct for 90-Degree Bends

Gain is the conduit you "save" when you bend a 90 instead of cutting two pieces and connecting them with a fitting. Because the bend curves through the corner, you use less conduit than the sum of the two straight legs.

The gain formula:

Gain = (2 x Deduct) - (Radius x 3.1416 / 2)

Or simplified: Gain = (2 x Deduct) - (Radius x 1.5708)

Gain matters when you're calculating cut lengths. If you need a piece of conduit to run 36 inches along the floor and then 24 inches up a wall, the total isn't 60 inches. It's 60 inches minus the gain. According to the Mike Holt bending reference, understanding gain prevents wasted material on every run that includes a 90.

Gain and deduct values for EMT 90-degree bends by conduit size

EMT Size	Deduct	Bend Radius	Gain
1/2"	5"	4"	3-3/4"
3/4"	6"	4-1/2"	4-7/8"
1"	8"	5-3/4"	6-15/16"
1-1/4"	11"	7-1/4"	10-5/8"

The Gain & Deduct Calculator generates these values for any conduit type and size, including IMC and rigid.

Worked Example: Offset Bend with Shrink

You're running 3/4" EMT along a wall and need to offset around a 4-inch-deep junction box. You want the first bend 24 inches from the end of the conduit. Here's the step-by-step calculation using a 30-degree offset.

Step 1: Find the Multiplier and Shrink

• Offset height: 4 inches
• Bend angle: 30 degrees
• Multiplier: 2
• Shrink per inch: 1/4"

Step 2: Calculate Mark Spacing

• Distance between marks = 4" x 2 = 8"

Step 3: Calculate Shrink

• Shrink = 4" x 0.25 = 1"

Step 4: Place Your Marks

• First mark: 24" + 1" (shrink compensation) = 25" from the end
• Second mark: 25" + 8" = 33" from the end

Step 5: Bend

Place the bender on the first mark, bend to 30 degrees, flip the conduit, place the bender on the second mark, and bend to 30 degrees in the opposite direction. The conduit offsets 4 inches and the far end still lands at the right spot because you accounted for shrink.

Saddle Bend Formulas

Saddle bends go over an obstruction and return to the original plane. There are two types: 3-point saddles and 4-point saddles.

3-Point Saddle

A 3-point saddle uses one center bend (typically 45 degrees) and two outer bends (22.5 degrees each) to create a symmetrical hump over an obstacle.

• Center bend angle: 45 degrees (most common)
• Outer bend angles: 22.5 degrees each
• Outer mark spacing: Obstruction height x 2.61 (from center mark, each direction)
• Shrink: Obstruction height x 3/16" per inch (for 22.5-degree outers)

4-Point Saddle

A 4-point saddle is essentially two offset bends placed back-to-back. It creates a rectangular jog over the obstruction. Use the same multiplier and shrink values from the offset chart above, applied twice.

• All four bends: Same angle (commonly 22.5 or 30 degrees)
• Mark spacing: Obstruction height x Multiplier for your chosen angle
• Total shrink: Double the offset shrink (because there are two offsets)

Conduit Bending Cheat Sheet: All Formulas at a Glance

Here's the full conduit bending cheat sheet. These are the formulas that cover every standard bend type you'll encounter on the job.

Master conduit bending formula reference for all bend types

Bend Type	Formula	Key Values
Stub-up (90°)	Mark = Stub height - Deduct	Deducts: 5", 6", 8", 11"
Offset	Spacing = Offset x Multiplier	30°: 2x, 45°: 1.41x, 60°: 1.15x
Shrink	Shrink = Offset x Shrink constant	30°: 1/4", 45°: 3/8", 60°: 1/2"
Gain (90°)	Gain = (2 x Deduct) - (R x 1.5708)	See Gain table by size
3-Point Saddle	Outer spacing = Height x Multiplier	45/22.5: spacing = Ht x 2.61
4-Point Saddle	Same as double offset	Double the shrink
Back-to-Back 90	Distance = Leg - Deduct - Deduct	Subtract deduct from each end
Segment Bend	DPI = Bend angle / Conduit length in bend	Used for large radius bends

NEC Bending Requirements

The National Electrical Code (NFPA 70) sets two important rules about conduit bends that directly affect how you use these formulas on the job.

360-Degree Rule

NEC Section 358.26 (for EMT) limits the total bending degrees between pull points to 360 degrees. That's four 90s, or any combination that adds up to 360 degrees. Offsets count toward the total, so a run with two offsets (four 30-degree bends = 120 degrees total) and three 90s (270 degrees) would hit 390 degrees and violate code. As the EC&M code Q&A explains, this restriction protects conductor insulation from excessive friction during wire pulls.

Minimum Bending Radius

NEC Chapter 9, Table 2 specifies minimum bending radii for each conduit type and trade size. Hand benders are manufactured to meet these minimums, so if you're using a standard bender you're compliant. Field bending with a hickey or bending larger conduit on a Chicago bender requires verifying you're meeting the minimum radius for your conduit size.

How Conduit Bending Makes This Easier

Conduit Bending is an iOS app built specifically for these calculations. Instead of memorizing charts or doing arithmetic on the job site, you select your conduit type, enter your measurements, and get exact bending marks.

What it handles that a chart can't:

• Any angle: Charts only cover standard angles. The app calculates multipliers and shrink for any degree value.
• Multiple conduit types: EMT, IMC, and Rigid all have different radii and deducts. The app's bender library includes all standard sizes from 1/2" to 4".
• Parallel bends: When you're bending multiple conduits side by side, each one needs different mark spacing to maintain uniform separation. The app calculates all of them.
• Fraction math: Results display in feet-inches-fractions, the format you actually mark on conduit. No decimal conversions needed.
• 16 bend types: Offsets, saddles, 90s, kicked 90s, rolling offsets, corner bends, and more.

Related Guides

• See these formulas in action: Offset Bend Guide, 3-Point Saddle Guide, and 90-Degree Bend Guide.
• For a deeper look at offset multipliers specifically, see the Bending Multiplier Chart.
• Starting from scratch? How to Bend Conduit covers every bend type with step-by-step instructions.

Common Mistakes with Bending Formulas

Knowing the formulas is half the battle. Applying them correctly in the field is the other half. Here are the mistakes that waste the most conduit.

• Forgetting shrink on offsets: This is the number one error apprentices make. You calculate the mark spacing correctly but forget to add the shrink to the first mark. The conduit comes up short every time.
• Using the wrong deduct for your bender: Not every bender uses the standard deducts. Some older or specialty benders have slightly different take-up values. Check the stamp on your bender frame before assuming.
• Confusing gain with deduct: Gain and deduct are related but not interchangeable. Deduct is for placing your mark. Gain is for calculating cut length. Using gain where you should use deduct will produce a stub-up that's several inches off.
• Not accounting for spring-back: Conduit springs back slightly after bending, especially on larger sizes. If your 90 measures 88 degrees after bending, over-bend slightly and check with a level. This varies by conduit wall thickness and is more pronounced with rigid than EMT.
• Exceeding the 360-degree rule: It's easy to lose track of total bend degrees on a long run, especially when offsets are involved. Count every bend. If you're close to 360 degrees, add a pull box or conduit body to reset the count.

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Frequently Asked Questions

What is the deduct for 1/2 inch EMT?

The standard deduct for 1/2 inch EMT with a hand bender is 5 inches. This means you subtract 5 inches from your stub-up height to find the mark where you place the bender arrow. For example, a 12-inch stub requires a mark at 7 inches from the end of the conduit.

What is the multiplier for a 30-degree offset bend?

The multiplier for a 30-degree offset bend is 2. Multiply the offset distance by 2 to find the distance between bend marks. For example, a 6-inch offset at 30 degrees requires 12 inches between marks. The formula is: distance between marks = offset height x multiplier.

How do you calculate shrink for an offset bend?

Multiply the offset height by the shrink per inch value for your bend angle. At 30 degrees, shrink per inch is 1/4 inch (0.25). So a 6-inch offset produces 1.5 inches of shrink. Add the shrink amount to your first bend mark distance from the end of the conduit to compensate.

What is gain in conduit bending?

Gain is the amount of conduit saved when making a 90-degree bend compared to using a fitting with two straight pieces. Because a bend curves through the corner rather than going straight to a coupling, the bent conduit is shorter than the sum of the two straight legs. The gain formula is: Gain = 2 x Stub Deduct - (Radius x pi / 2). Gain values vary by conduit size and bender type.

What is the 360-degree rule for conduit bends?

NEC Section 358.26 (for EMT) limits the total degrees of bends between pull points to 360 degrees. This equals four 90-degree bends maximum in a single conduit run between boxes, conduit bodies, or other accessible pull points. The rule exists to protect conductor insulation from excessive friction during wire pulls.