Rolling Offset Calculator
Solve pipe rolling offsets like a fitter. Enter the horizontal and vertical offsets in inches and pick the fitting angle (22.5°, 30°, 45°, or 60°), and get the true offset, the travel (center-to-center pipe length), and the run.
Example: with Horizontal offset (inches) 15 · Vertical offset (inches) 8 · Fitting angle 45° fittings → Travel (center to center): 24.04 in (≈ 24 1/16 in).
- True offset17.00 in
- Run17.00 in
Computed by the calculator below using its default values. Change any input to see your own numbers.
True offset = √(horizontal² + vertical²); travel = true offset × 1.414 for 45° fittings. Subtract fitting takeouts before cutting.
What makes an offset a rolling offset
A simple offset shifts pipe in one plane — over, or up. A rolling offset shifts in two planes at once: the pipe must move sideways and change elevation between the same pair of fittings. The trick fitters use is to collapse the two offsets into one: the true offset is the diagonal of the rectangle they form, √(horizontal² + vertical²). From there it behaves exactly like a simple offset — travel (the center-to-center length of the angled pipe) is the true offset divided by the sine of the fitting angle, and the run it consumes along the main direction is true offset divided by the tangent.
With a 15-inch roll and an 8-inch rise, the true offset is 17 inches; through 45° fittings the travel is 17 × 1.414 = 24.04 inches.
From travel to a cut length
Travel is measured center of fitting to center of fitting. To get the actual pipe cut, subtract each fitting's takeout — the distance from its center to where the pipe seats — for both ends. Takeouts depend on fitting size, angle, and type (butt-weld, threaded, pressed), so pull them from the manufacturer's chart or measure. Lower-angle fittings trade longer travel for gentler flow: the same 17-inch true offset needs 44.4 inches of travel through 22.5° fittings but only 19.6 through 60s.
How it’s calculated
True offset = √(horizontal² + vertical²). Travel = true offset ÷ sin(fitting angle); run = true offset ÷ tan(fitting angle). For 45° fittings that means travel = true × 1.4142 and run = true × 1.0000. Fractional readout rounds to the nearest 1/16 inch.
Travel is center-to-center — actual cut length requires subtracting each fitting's takeout, which varies by pipe size and fitting type.
Offset multipliers by fitting angle
| Fitting angle | Travel = true × | Run = true × |
|---|---|---|
| 22.5° | 2.613 | 2.414 |
| 30° | 2.000 | 1.732 |
| 45° | 1.414 | 1.000 |
| 60° | 1.155 | 0.577 |
Computed as 1/sin(angle) and 1/tan(angle) — the standard pipefitter multiplier table.
Common mistakes
- Cutting pipe to the travel length without subtracting fitting takeouts at both ends.
- Using only the horizontal offset and discovering the pipe also needed to climb 8 inches.
- Applying the 45° multiplier (1.414) to 22.5° fittings, which need 2.613.
- Measuring offsets to pipe surfaces instead of centerlines — all of this math runs center to center.
Frequently asked questions
What is the rolling offset formula?
True offset = √(horizontal² + vertical²), then travel = true offset ÷ sin(fitting angle) and run = true offset ÷ tan(angle). With 45° fittings, travel is simply true offset × 1.414.
What is the difference between travel and run?
Travel is the length of the angled piece of pipe, center of fitting to center of fitting. Run is how much straight-line distance along the original direction that angled section uses up. Travel is what you cut; run is what you lay out.
Why does the 45 multiplier equal 1.414?
It is 1 ÷ sin(45°) = √2. The 45° offset forms an isosceles right triangle, so the diagonal (travel) is the true offset times √2, and run exactly equals the true offset.
Do I subtract fittings from the travel?
Yes — travel is center-to-center, and each fitting occupies some of it. Subtract the takeout (center-to-face engagement) for the fitting size and type on both ends to get the end-to-end pipe cut.