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Android app

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Back-to-Back 90° Bend Calculator

Measure the back-to-back distance from the back of the first 90. Either put the bender's star point on that mark with the bender reversed, or subtract the take-up and put the arrow there with the hook facing the first 90.

  • Star or arrow
  • 1/2" to 1-1/4" EMT
  • U-bends and frames

Mark the second 90

Star-point or arrow method
Outside of one 90 to the outside of the other
The deduct on your shoe, if it differs
Centerline radius from the shoe or its maker, for the U length and the width check
With the second stub, gives the cut length
Both measured to the outside back of the 90s
Star mark (from back of first 90)
30"
or arrow mark
25"
Take-up used
5"

Radius used: 4-5/8" (Klein 51606). Geometric minimum width: 9-15/16"; your bender's hook and shoe may need more room.

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Hook the tape on the back of the first 90. Use one: star point on ★ with the hook facing away from the first 90, or the arrow on A with the hook facing the first 90. With the arrow method the first leg swings toward you: keep clear of it.

Cut length = stub 1 + distance + stub 2 − 2 × gain, with gain = radius × (2 − π/2) + conduit OD, all measured to the outside backs of the bends (ideal circular bends).

The app saves the shoes you own with their take-up and radius, does both 90s from the end of the stick, and draws which way the hook faces for each mark.

See it in the Android app →

Method and sources

By Blissom · Updated 2026-10-23

Layout values: check them against your own bender, on scrap first.

Short answer: bend the first 90 as a normal stub. Measure the back-to-back distance from the back of that 90 and mark it. Star-point method: star on the mark, bender reversed. Arrow method: mark the distance minus the take-up instead, arrow on it, hook toward the first 90.

back-to-back distance12
Measure outside to outside ("back to back"). The first 90 is a normal stub; the second is marked from the back of the first.

How to bend back-to-back 90s

  1. Bend the first 90 as a stub-up: stub height minus take-up from the end.
  2. Measure from the back of the first 90 (the outside of the vertical leg) along the pipe, and mark the back-to-back distance.
  3. Place the bender using one of the two methods below and bend the second 90 in the same plane, so both legs point the same way.
  4. Check the finished U (see the checklist below).

Star point or arrow

Both methods put the second 90 in the same place; use whichever your bender and habit favor, but never mix them on the same bend.

  • Star point: mark the full back-to-back distance, reverse the bender so the hook faces away from the first 90, and put the star on the mark.
  • Arrow: mark the back-to-back distance minus the take-up, and put the arrow on it with the hook facing the first 90. Klein take-ups: 1/2" 5", 3/4" 6", 1" 8", 1-1/4" 11"; other makers and models can differ, so use the number on your shoe (the calculator takes your own).

Caution with the arrow method: the leg you already bent swings toward you during the second bend. Keep your body clear of it, keep control of the conduit, and follow the bender maker's instructions. For 1-1/4" EMT, check that your bender is rated for that size; larger EMT may need a mechanical or powered bender with its own marks and deduct.

How much conduit a U needs

Conduit needed ≈ first stub + back-to-back distance + second stub − 2 × the gain of a 90 measured to the back. On a Klein 51606 1/2" EMT shoe (4-5/8" centerline radius, 0.706" OD) that gain is about 2-11/16" per 90; shoes with a different radius differ, so check yours.

gain per 90 = R × (2 − π/2) + OD
cut length = H1 + D + H2 − 2 × gain

R is the shoe's centerline radius, OD the conduit's outside diameter, D the outside-to-outside distance and H1, H2 the finished stub heights, all measured to the outside backs of the bends. This is the geometry of ideal circular bends, not a promise that a hand bend finishes within 1/16", so cut a little long and trim the second stub.

Worked example: a U between two boxes on 3/4" EMT

Two boxes need 12" stubs, and the outside of one 90 to the outside of the other has to be 36". These are finished conduit dimensions, to the bare ends and the outside backs of the bends; if you measure between boxes, allow separately for the connectors and how far they enter the box.

  1. First 90: 12" − 6" take-up = arrow at 6" from the end. Bend it.
  2. Second 90: measure 36" from the back of the first 90. Put the star point on that mark with the bender reversed, or put the arrow at 36 − 6 = 30" with the hook facing the first 90.
  3. Conduit needed: 12 + 36 + 12 = 60" of legs, minus 2 × 3.283" of gain on a Klein 51607 (5-1/2" radius) = 53-7/16". Cut a little long and trim the second stub.

Check the finished U

  • Both bends read 90° on a level after spring-back.
  • Both legs are parallel and in the same plane: lay the U on the floor and it should sit flat.
  • Outside to outside reads the back-to-back distance.
  • Neither bend is kinked, cracked or visibly flattened (NEC 2023 358.24(A)).
  • Cut ends are square and deburred before the connectors go on.

Two 90s add 180° toward the 360° limit between pull points (NEC 2023 358.24(B) for EMT (358.26 in NEC 2020)); the 2026 NEC adds 300.24 for runs that combine raceway types. A U that measures right is not by itself proof the run meets code.

Mistakes

  • Measuring from the inside of the first 90 instead of the back.
  • Using the arrow on the full distance: the U comes out a take-up too wide.
  • Bending the second 90 out of plane, so the legs are not parallel. Stand the first stub against a wall or have someone sight it.

Sources: NEC 2023 358.24 and Chapter 9, Table 2; Klein Tools Conduit Bender Guide (stub take-up, offset multipliers and shrink, saddles); Klein Tools Conduit Bending Basics (90° stub-up take-up table: 5", 6", 8", 11"). Method.

Questions electricians ask

Why is my finished U too wide or too narrow?

Usually the take-up you used does not match your shoe, the distance was measured from the inside of the first 90 instead of its back, the arrow was put on the full distance, or the second bend stopped short of or went past 90°. Check your take-up on scrap and measure every dimension to the outside backs.

Can two 90s fit in a narrow U?

Only down to a limit set by the shoe. With ideal circular bends the outside-to-outside width cannot be less than 2 × the centerline radius + the conduit OD: about 9-15/16" for 1/2" EMT on a Klein 51606 (4-5/8" radius) and 11-15/16" for 3/4" on a Klein 51607 (5-1/2"). The shoe and hook need more room than that, so a narrower U needs fittings or a different layout. The calculator checks the ideal geometric minimum from the centerline radius and conduit OD; it cannot tell whether your bender’s hook and shoe have room, so check that before bending.

What is the star point on a bender used for?

The star point marks the back of a 90 with the bender reversed. Put the star on your back-to-back mark and bend; the back of the new 90 lands on the mark. It saves subtracting the take-up. If your bender has no star, use the arrow method.

Can I do back-to-back 90s with the arrow?

Yes. Subtract the take-up from the back-to-back distance, mark that distance from the back of the first 90, and put the arrow on it with the hook facing the first 90. It is the same as bending a stub measured from the first 90.

How long a piece of conduit do I need for a U?

Add the two stub heights and the back-to-back distance, then subtract the gain of both 90s. For 1/2" EMT on a Klein 51606 (4-5/8" radius), the gain to the back of a 90 is about 2-11/16", so a 12" / 30" / 12" U needs about 54 − 2 × 2.691 = 48-5/8". Connectors and box entries are extra: this is the bare conduit.

Conduit Bending Calculator app screen

The whole U from one end of the stick

  • First stub, second 90 and the conduit length in one screen
  • Tape strip shows which way the hook faces for each mark
  • Your shoe's take-up and radius, EMT or rigid
  • Save it as a job and share a PDF with the crew

Android only. There is no iPhone version yet; the free calculators on this site work on any phone.

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