90° Bend Calculator

The 90° bend is the foundation everything else is built on: stub-ups, kicked 90s, offsets that turn corners, back-to-back U-bends. Understand what a 90° does to a stick of conduit and every other bend gets easier.

Anatomy of a 90° bend

A 90° has two tangent points — where the straight conduit meets the curve — an arc between them (arc length = π/2 × centerline radius R), and the back of the bend, the outside corner your measurements reference. For a stub-up, you mark at target height − take-up (5" for 1/2" EMT on a standard hand bender), put the arrow on the mark, and bend: the back of the bend lands exactly at target height.

Gain: the hidden number

Bending 90° does not just redirect the conduit — it uses up some of it. The arc is shorter than the two straight legs it replaces, by an amount called gain: roughly 0.43 × R for a 90°. On 1/2" EMT (R ≈ 4.31") that is about 1-7/8" per bend. Gain matters whenever you cut a stick to an exact developed length with 90s in it — ignore it and the run comes up short.

Back-to-back 90s

Two 90s facing each other make a U that jumps between two parallel runs — up and over a doorway header, for example. Layout is simple: mark the first 90 at (H1 − take-up) from the end, then mark the second 90 exactly W farther along, where W is the desired distance between the backs of the bends. With H1 = 18", H2 = 24", W = 36" and 3/4" EMT (take-up 6"): Mark 1 at 12" from the end, Mark 2 at 48" from the end. Both bends keep the same take-up, so the marks land W apart and the backs land W apart.

Checking your 90°

• Hold a square against the inside of the bend — both legs should touch.
• Measure the stub height to the back of the bend, not the inside corner.
• If the angle is under 90°, the stub comes out tall; over 90°, it comes out short. Small errors here become big ones at the box.
• A kinked 90° is scrap. If the conduit starts to flatten, stop — you are past what that bender and size can do.

When 90s stack up

Runs with several 90s accumulate both gain and small angle errors. Add up the gain for every bend before cutting, bend the 90s before any offsets in the same stick when you can, and verify each bend with the square before moving to the next. The calculator's feasibility check warns you before a bend is too tight to make.