Offset angle calculator
The offset calculator starts from an angle. This one starts from the room you have: a rise that is fixed, and only so much pipe between a box and a beam, or a coupling and a strap, to make it in. Type both and it gives the one angle that fills the space, the marks for it, and the nearest standard angle that still fits if you would rather bend a number you know.
Measure it
- Rise. Centre of the pipe where it runs now to centre of where it has to end up — the same rise as any offset.
- Space. Along the run, from the first point bend 1 is allowed to start to the last point bend 2 has to be finished by. That is the room the jog can use.
- Read. The angle goes on both bends. Put mark 1 where the space begins and mark 2 the between-marks distance past it; the jog lands inside the space.
- Length. The shrink goes on the overall length, as for any offset — see the shrink calculator.
Worked examples
Between a box and a beam
The run has to step down 8" (203 mm) to clear a beam, and there is only 14" (356 mm) between the box connector and the beam's edge. atan(8 ÷ 14) = 29.7°. The marks are √(8² + 14²) = 16 1/8" (410 mm) apart and the offset shrinks 2 1/8" (54 mm). Or bend 30°: marks 16" (406 mm) apart, and the jog uses 13 7/8" (352 mm) of the 14" (356 mm).
Lots of room, small rise
A 2" (51 mm) kick over a flange with 24" (610 mm) to play with: atan(2 ÷ 24) = 4.8°. That is shallower than any chip, so the calculator offers 10° — marks 11 1/2" (293 mm) apart, 3/16" (4.4 mm) shrink, using 11 5/16" (288 mm) of the room. Either works; the shallow one is easier to pull wire through.
A metric job
5 7/8" (150 mm) of rise inside 10 1/4" (260 mm): atan(150 ÷ 260) = 30.0°, marks √(150² + 260²) = 11 13/16" (300 mm) apart, shrink 1 9/16" (40 mm).
Run each angle uses
For every unit of rise, a bend of this angle travels this far along the run (1 ÷ tan θ). Multiply by your rise: if the answer is more than your space, that angle does not fit.
| Angle | Run used per unit of rise |
|---|---|
| 10° | 5,67 |
| 22,5° | 2,41 |
| 30° | 1,73 |
| 45° | 1,00 |
| 60° | 0,58 |
The formula
angle = atan(rise ÷ space) · between marks = √(rise² + space²) · shrink = between marks − space
The two marks and the rise make a right triangle whose flat side is the space, so the angle, the mark spacing and the shrink all come straight from the two numbers you measured. The marks are the centres of the bends, the same reference as every other calculator on the site.
Which bender these numbers assume — and how to adjust
The geometry belongs to the angle, not the tool. What the tool changes — its reference marks, its take-up and gain, its springback — is yours to read off the shoe or prove on scrap, never a table here (the four test bends). For this bend:
For an offset both marks go on the arrow, which on a hand bender is the start of the bend, and both bends are pulled to the same degree line on the shoe. Nothing else about the bender enters the numbers: the multiplier and the shrink are pure angle. If your bender has no degree scale, or you doubt it, put a level or a protractor on the pipe after the first bend and read the real angle — then use "Other angle" above so the second mark matches what you actually pulled.
Questions
- How do I find the angle for an offset when the space is tight?
- Measure two things: the rise (how far the pipe has to move over) and the space along the run the jog can use. The angle is the arctangent of rise ÷ space. An 8 inch rise in 14 inches of room is atan(8 ÷ 14) = 29.7° — bend both bends to that on the degree marks and the offset fills the space exactly.
- Can I just use the next standard angle instead?
- Yes, and it is often easier to repeat. Use the shallowest chip angle at or above the exact one: a steeper bend covers less run, so it still fits, and the shallowest one that fits shrinks the least. For 29.7° that is 30°, which uses about 13 7/8 of the 14 inches.
- Why not a shallower angle?
- A shallower bend needs more run to make the same rise. At 22.5° an 8 inch rise covers 8 ÷ tan 22.5° ≈ 19.3 inches along the pipe — it would run straight into whatever is at the end of your 14 inches.
- What if the exact angle comes out over 60°?
- Then the space is very short for the rise and the offset is close to a pair of 90s. The bends get hard to place accurately and the pipe is harder to pull through. Look for more room along the run, drop the rise, or route around.