Conduit offset math practice
Given a rise and a bend angle, work out the centre-to-centre distance between the two bends. Type it in and it is marked, with the multiplier and the working shown when you miss. A field rounding still counts.
This drill needs JavaScript to generate and mark questions. Turn it on to practice — the explanation below works either way.
The maths behind it
An offset is two equal bends that step the pipe over by a rise. The distance you mark between them is the rise times the offset multiplier, where the multiplier is 1 ÷ sin of the bend angle. For a 6" offset at 30°, the multiplier is 1 ÷ sin 30° = 2.0, so the marks are 6 × 2.0 = 12" apart. At 45° the multiplier is about 1.414; at 22.5°, about 2.613. The trade carries rounded versions of these in its head, and they are close enough to mark a pipe by.
Questions people ask
What is the offset multiplier?
It is 1 ÷ sin of the bend angle, and it turns the offset you need into the distance between the two bends. At 30° it is 2.0, at 45° about 1.414, at 22.5° about 2.613, at 60° about 1.155. Multiply your rise by it and you have the centre-to-centre mark spacing.
Where does the field rule of thumb fit?
The trade rounds the multipliers to memorable numbers — 2 for 30°, 1.4 for 45°, and so on. The drill marks against the exact trig value but a rounded field answer still lands inside the tolerance, which is the honest way to practise it.
Is this the same as the bending calculators elsewhere?
No — this drills the maths, it does not do your job for you. It generates a rise and an angle and asks you for the spacing. When you are actually at the bender and want the numbers worked for a real pull, that is what bentright.com is for.
Related
- Formula sheets — the multipliers and shrink, printable for your pouch.
- Glossary: shrink — the other half of the offset bookkeeping.
- At the bender for a real pull? bentright.com works the numbers.
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