Piping
Rolling offset calculator
In short
A rolling offset shifts a line both up (V) and sideways (H) with two elbows. The true offset S = √(V² + H²) is handled like a plain offset: travel T = S / sin α, cut length L = T − 2E − 2j, and both elbows are rolled φ = atan(H / V) from vertical.
Calculation
Example calculated with the tool’s default values.
Inputs
- Pipe
- DN50 · 60.3 × 2.9 mm
- Vertical offset (axis to axis)
- 300 mm
- Horizontal offset (axis to axis)
- 400 mm
- I know
- The elbow angle
- Elbow angle
- 45°
- Elbow radius
- Bought long-radius elbow (EN 10253-2 3D or ASME B16.9 LR per pipe)
- Root gap
- 0 mm
- Elbow to cut from
- Smallest that fits
- Marks around
- 16
Results
- Cut length
- 644.1 mm
Worked example
Every value in this section belongs to the example, calculated with the tool’s default values.
Other results of the example
- True offset
- 500.0 mm
- Travel
- 707.1 mm
- Run
- 500.0 mm
- Elbow angle
- 45.00°
- Elbow roll (from vertical)
- 53.1°
- Elbow take-out
- 31.5 mm
- Radius used
- 76.0 mmEN 10253-2 3D elbow
- Roll both elbows 53.1° from vertical, the same way, before tacking.
Step-by-step calculation
True offset
S = √(V² + H²)
√(300.0² + 400.0²) = 500.0 mm
Travel
T = S / sin α
500.0 / sin 45.00° = 707.1 mm
Run
A = S / tan α
500.0 / tan 45.00° = 500.0 mm
Elbow take-out
E = R × tan(α / 2)
76.0 × tan 22.50° = 31.5 mm
Cut length
L = T − 2E − 2j
707.1 − 63.0 − 0.0 = 644.1 mm
Elbow roll
φ = atan(H / V)
atan(400.0 / 300.0) = 53.1°
How to use it
- Pick the pipe: outside diameter and wall thickness.
- Enter the vertical and horizontal offsets, measured axis to axis.
- Say what you know: the elbow angle (1° to 90°) or the required run along the line.
- Pick the elbow radius (1.5 D, 1 D, EN 10253-2, ASME B16.9 or custom) and the root gap.
- Read the cut length.
Frequently asked questions
What is the rolling offset formula?
Both offsets are combined into the true offset S = √(V² + H²). With the elbow angle α: travel T = S / sin α, run A = S / tan α, elbow take-out E = R × tan(α / 2), then cut length L = T − 2E − 2j, where j is the root gap.
What is the 45 degree rolling offset formula?
Example with V = 300 mm and H = 400 mm: true offset √(300² + 400²) = 500 mm, travel 500 / sin 45° = 707.1 mm, run 500 / tan 45° = 500 mm. For a 60.3 × 2.9 pipe with long radius elbows (R = 1.5 × OD = 90.4 mm), each elbow takes out 37.5 mm: cut length 707.1 − 74.9 = 632.2 mm with no root gap.
How far do I roll the elbows on a rolling offset?
The plane holding both elbows is tilted φ = atan(H / V) from vertical. In the example, atan(400 / 300) = 53.1°: roll both elbows 53.1° from vertical, the same way, before tacking.
What if the run is fixed?
Choose "The required run" and enter it: the elbow angle is then worked out, α = atan(S / A). If that angle is neither 45° nor 90°, each elbow is cut from a stock elbow and the calculation gives the cut layout.
Limits
Indicative results. The 1.5 D and 1 D radii are approximated on the outside diameter; EN 10253-2 and ASME B16.9 elbows use the radius from the tables. Outside 45° and 90°, the elbow is cut from a 90° elbow and its take-out is taken as R × tan(α / 2). Check the dimension on your elbows before cutting.
Sources
- Géométrie du dévoiement : Trigonométrie du triangle rectangle (T = S / sin α, A = S / tan α, E = R × tan(α / 2))
- EN 10253-2:2021+A1:2026 (raccords à souder bout à bout) : Coudes 2D/3D (rayon R), tés égaux (F), réductions (L) ; tableaux Zickwolff, consultés le 08/11/2026 (link)