Conduit BendingAbout this site
Updated 2026-09-29
conduitbending.app is built by Blissom, the small studio behind the Conduit Bending Calculator app for Android. The website gives electricians and apprentices the everyday bending math for free; the app carries the full toolkit onto the job.
How the math is checked
Every calculator on this site runs the same calculation engine as the app, and that engine is covered by an automated test suite (88 tests at the last release) that checks, among other things:
- Offset spacing and shrink against the trade constants stamped on hand benders (10° = 6 and 1/16", 22.5° = 2.6 and 3/16", 30° = 2 and 1/4", 45° = 1.4 and 3/8", 60° = 1.2 and 1/2") and against exact trigonometry.
- 3-point saddle constants (2.5 and 3/16" for 45°, 2.0 and 1/4" for 60°, 1.4 and 3/8" for 90°).
- Stub-up and back-to-back marks against the published take-ups (5", 6", 8", 11").
- Conduit fill counts against NEC Annex C (for example 9, 16 and 26 #12 THHN in 1/2", 3/4" and 1" EMT) and box fill against Table 314.16(A) and (B), including the 2020 rule for grounds beyond four.
- Rejection of inputs that cannot be bent: angles outside 0–90°, offsets too shallow for the shoe, stubs shorter than the take-up.
Every worked example in the guides was recalculated with the engine, and the results were checked against the app running on a device.
Sources
- NFPA 70, National Electrical Code: Chapter 9 Tables 1, 2, 4 and 5 and Note 7; 314.16; 358.24 and 358.26. Values match the 2020 and 2023 editions.
- Hand-bender manufacturer data for take-up (deduct) and the star, arrow and notch marks.
- Standard trigonometry: cosecant for the multiplier, tangent of the half angle for shrink.
What these tools are, and are not
They are estimating aids for trained electricians and apprentices. Always check marks against the deduct stamped on your own bender, and follow the code edition and local amendments your inspector enforces. This site is not affiliated with the NFPA or any bender manufacturer; brand names belong to their owners.
Found a mistake?
Leave a review or a question on the app's Google Play listing. Corrections are made on the site and in the app together, and the date at the top of each page shows when it was last reviewed.