BendPro

Conduit Bending Math, Without the Index Card

Every electrician learns the offset multipliers and the take-up values somewhere — trade school, an apprentice handbook, or a 3×5 card taped to the side of the bender. Most of us still keep that card, because remembering that 30° offsets multiply by 2.0 and shrink 1/4" per inch of offset, while 22.5° offsets multiply by 2.6 and shrink 3/16" — when you also have to remember Klein's 1/2" EMT take-up is 5", but Greenlee's RMC bender is 6" — is exactly the kind of detail that disappears the moment you're holding a 10-foot stick of conduit and a foreman is asking what mark to draw. BendPro replaces the index card with one app that does the math live, in front of you, with a labelled diagram showing what every number means.

The Six Bends That Cover 95% of Conduit Work

Most commercial and residential conduit runs come down to six bend types: the offset (two equal-angle bends to step the run around an obstacle), the rolling offset (an offset that travels horizontally AND vertically at the same time), the 3-point saddle (two outer bends and a centre bend at twice the angle, used to skip over a single obstruction), the 4-point saddle (two equal offsets back-to-back around a wider obstacle), the 90° stub-up (a single 90° bend producing a vertical leg), and the kick (a small angled bend that picks the run up off a deck or away from a box). BendPro has a dedicated calculator for each one, with the right inputs, the right outputs, and a diagram that labels every angle and mark.

Offset Multipliers, Explained

An offset bend uses two equal-angle bends to shift the conduit by a target depth. The distance between the two bend marks is the offset depth times a multiplier that depends on the angle: 1/sin(angle). For 30°, sin(30°) = 0.5, so the multiplier is 2.0 — you mark twice the offset depth. For 45° it's about 1.41, for 22.5° about 2.6, for 10° about 5.76. The smaller the angle, the more conduit you use to make the offset and the less the run shrinks. BendPro shows the multiplier on every offset result so you can sanity-check the calculation against your trade-school memory.

Why Take-Up Matters on a 90° Stub

When you bend a 90° in a piece of conduit, the bend isn't a perfect right angle at a single point — it's a curved arc with a radius matched to your bender shoe. The "take-up" (sometimes called "deduction") is how much the bend "uses up" of the conduit between the start of the bend and the back of the 90°. To make a 12" stub on 1/2" EMT with a Klein bender (5" take-up), you measure 7" from the end of the conduit and place your mark there. With a Greenlee Rigid bender (6" take-up on 1/2"), you'd measure 6". Use the wrong take-up and your stub is off by an inch. BendPro reads the take-up directly from the manufacturer's published table for the bender brand and conduit size you select.

Rolling Offsets and the Pythagorean Trick

A rolling offset is what you use when a run has to step over AND step sideways in one motion — think conduit running along a beam that has to drop down and roll out around a column. The "true" offset (the distance the conduit actually moves) is the Pythagorean diagonal: √(horizontal² + vertical²). The roll angle (how much you twist the conduit between the two bends) is arctan(horizontal / vertical). BendPro does both calculations and shows you a top-down view (the H/V crosshair) and a side view (the bend angle) so you can visualise both motions at once.

3-Point and 4-Point Saddles for Obstructions

When you have to clear an obstruction in the middle of a run — a beam, a duct, a smaller pipe — a saddle is what you reach for. A 3-point saddle is the simpler version: a centre bend at twice the angle, two outer bends at half the centre angle, with a standard 22.5°/45°/22.5° configuration shrinking 3/16" per inch of saddle depth. A 4-point saddle is two offsets back-to-back, used when the obstruction is wider than a 3-point can clear cleanly. BendPro calculates both, returns the exact mark spacing for the saddle depth and obstruction width you enter, and draws the obstacle in the diagram so you can see how the conduit clears it.

Wire Fill: the NEC Chapter 9 Calculator

The 2023 NEC Chapter 9 caps the cross-sectional area of insulated conductors inside a conduit at a fraction of the conduit's interior area: 53% for one wire, 31% for two, and 40% for three or more (Note 4). BendPro's wire-fill calculator picks the right limit based on the conductor count you enter, looks up the conduit interior area from Table 4 (EMT, IMC, RMC, PVC schedule 40, all common trade sizes), looks up the conductor area from Table 5 (THHN/THWN-2 and XHHW for AWG 14 through 4/0), totals everything up and shows the fill percentage with the NEC limit drawn on a coloured bar. Over-fill flips to red — pull a larger pipe.

Bender Brands and Custom Profiles

BendPro ships with deduction tables for Klein Tools, Greenlee, Ideal Industries and Gardner Bender — the four brands that cover most North American electrical contractors. EMT and rigid/IMC variants are both included where the manufacturer publishes separate values. If your shop runs a brand that isn't listed (Premium feature), you can add a custom bender profile with the take-up and gain values stamped on the shoe — once added, every calculator can use it.

History, Favorites, and Sharing

Every calculation is saved automatically — the inputs you typed, the outputs the app produced, the conduit size and bender brand. Open any saved entry to recalculate at a different angle, or one-tap the bookmark to favorite it for the next time you're running the same job. Premium unlocks unlimited favorites, unlimited history, and diagram export — a labelled image you can drop in a text or share to the apprentice doing the cuts.

Inches, Millimetres, and Reading the Marks

Default display is imperial fractions to 1/16" — the same precision you'd read off a Stanley tape (12-3/16" reads as 12-3/16, not 12.1875). One toggle in Settings switches the entire app to metric millimetres for international jobs or for working off mm-marked European tape. The bender deduction values convert automatically — Klein's 5" take-up becomes 127 mm, no manual maths.

Dark Mode and the Job Site

Default theme is dark, because the places electricians actually use a phone — basements, attics, plenums, the back of a panel, a roof at sunset — are not well-lit. Buttons are big enough for gloved fingers, fonts read clearly without squinting, and the contrast holds up under direct daylight if you do find yourself in it. The app is one-handed-friendly so you can hold a piece of conduit in your other hand.

Privacy and Offline Use

BendPro stores every calculation, every saved bend, and every setting locally on your device. No account, no cloud sync, no analytics, no tracking. The whole app loads instantly — no spinners, no waiting — and works completely offline, which matters when you're three storeys underground in a parking garage with concrete walls and no signal.

Phone, Tablet, and the Trade

On phones, BendPro uses a clean single-column layout sized for one-handed use. On tablets — useful for shop estimating or reviewing larger plans — content centres with comfortable margins so the diagrams have room to read clearly. Works on Android 8 (Oreo) and later. Designed by ClearStack Apps for working electricians, electrical apprentices, and DIY homeowners running their own conduit.