Pipe Offset Calculator: Travel and Set-Back for Parallel and Rolling Offsets, and Mitre Cuts

Work out the pipe length for an offset or a mitre.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

For a parallel offset, enter the offset distance and the fitting angle. The travel is the offset over sin of the angle, and the run is the offset over tan of the angle.

For a rolling offset, enter the rise and the roll. The calculator finds the true offset (the hypotenuse), then the travel and run in the tilted plane.

For a mitre, enter the change of direction and the pipe diameter to get the cut angle and the length of the cut.

Formulas used

  • T = \frac{S}{\sin\theta}
  • \text{run} = \frac{S}{\tan\theta}
  • S = \sqrt{\text{rise}^2 + \text{roll}^2}
  • \alpha = \theta/2

Worked example

With the default numbers in the calculator above:

  1. Travel: the centre to centre length of pipe between the two fittings: 424.26 mm
  2. Run (set-back): how far along the pipe the offset takes: 300.00 mm
  3. Multiplier for this fitting angle: 1.41 (travel = offset times this; 1.414 at 45 degrees, 2 at 30, 2.613 at 22.5)

Change the numbers in the calculator to see the full working, every step, for your own case.

A second worked example

A different case, with these numbers: What do you want? Rolling offset.

  1. True offset: the sideways distance in the tilted plane of the offset: 360.56 mm
  2. Angle the offset is rolled from the horizontal: 33.69 degrees
  3. Travel: the centre to centre length of pipe between the two fittings: 509.90 mm
  4. Run (set-back): how far along the pipe the offset takes: 360.56 mm
  5. Multiplier for this fitting angle: 1.41 (travel = offset times this; 1.414 at 45 degrees, 2 at 30, 2.613 at 22.5)

Common questions

What is the multiplier for a 45 degree offset?

1.414. The travel is 1.414 times the offset.

What is a rolling offset?

An offset in which the pipe moves both up and sideways at the same time.

Is the travel the cut length?

No. Subtract the take-off of the two fittings, which depends on their size and type.

How is a mitre cut?

Each piece is cut at half of the change of direction, so the two faces meet.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any pipefitter's handbook (offsets and rolling offsets); AS 4041 Pressure piping.

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