How to use this calculator
- Enter rise and roll. Measure the two perpendicular centerline moves that make up the rolling offset.
- Choose fitting angle. Select 22.5, 30, 45 or 60 degrees, or enter a custom fitting or miter angle.
- Enter fitting takeout. Use actual center-to-end takeout per fitting from the fitting, drawing or manufacturer data.
- Check travel and advance. Review true offset, center-to-center travel, cut length, advance, roll angle and straight-run margin.
How it works
A rolling offset combines two perpendicular moves. The true offset is the
hypotenuse of those rise and roll dimensions:
O_t = sqrt(V^2 + H^2)
where V is rise or set and H is roll.
Once the true offset is known, the two equal fittings use the same multiplier as any centerline offset: M = 1 / sin(a) L_c = O_t x M The calculator also reports advance along the run: A = O_t / tan(a) and the roll angle: phi = atan(H / V)
The pipe cut length subtracts actual fitting takeout from both ends: L_cut = L_c - 2T Use the pipe bend developed length calculator for bent-spool arc length and setback, the pipe miter cut calculator for wrap-around template marks on fabricated miters, the pipe saddle cut calculator for centered branch and lateral coping templates, the pipe reducer offset calculator for concentric and eccentric size-change layout, the pipe slope calculator for invert layout, the pipe pressure drop calculator for hydraulic loss, the pipe support span calculator for hanger spacing and the steel pipe schedule chart for actual steel pipe dimensions.
Worked example
Verified against the live calculator
With a 12 in rise and 16 in roll, the
true offset is 20 in. Two 45 degree
fittings use a 1.414 multiplier, so center-to-center travel is
28.28 in. If each fitting has 1.50 in
takeout, cut length is 25.28 in. Advance is
20 in, and the roll angle is 53.13 degrees.
Frequently asked questions
How do you calculate a pipe rolling offset?
First combine the rise and roll into a true offset: true offset = sqrt(rise^2 + roll^2). Then divide by sin(fitting angle) to get the center-to-center travel between fitting centers.
What is the rolling offset multiplier?
The multiplier is 1 / sin(angle). Common values are about 2.61 for 22.5 degrees, 2.00 for 30 degrees, 1.41 for 45 degrees and 1.15 for 60 degrees.
How is pipe cut length different from travel?
Travel is center-to-center fitting geometry. Cut length subtracts fitting takeout from both ends, so cut length = travel - 2 x takeout. Enter takeout from the actual fitting or shop detail.
Is this a fitting takeout chart?
No. It is a formula-only centerline layout calculator. Fitting takeout, socket depth, thread engagement, weld gap, bevel and manufacturer dimensions must come from the actual fitting, drawing or submittal.
Method & assumptions
- Uses ideal pipe centerline geometry for two equal-angle fittings or miters.
- Rise and roll are perpendicular centerline moves; zero roll reduces the problem to an ordinary flat offset.
- Fitting takeout is entered by the user because takeout depends on fitting type, size, material, end prep and manufacturer.
- Does not include fitting charts, bend developed length, miter template marks, weld gap, bevel, socket depth, thread engagement, field fit-up, thermal movement, supports, slope, code checks or inspection requirements.