What is a pipe notching calculator used for?

A pipe notching calculator computes the curved saddle profile that must be cut at the end of a branch pipe so it fits flush against the curved outer surface of a main pipe. The result is a printable wrap-around template: wrap it around the branch pipe, scribe the curved cut line, then cut with an angle grinder, bandsaw, or pipe notcher.

What is the formula for a pipe saddle cut?

For a branch pipe at intersection angle α to the main pipe, the axial cut position t at circumferential angle θ is: t(θ) = [r_b × sin(θ) × cos(α) + √(r_m² − r_b² × cos²(θ))] ÷ sin(α). For the 90° special case this simplifies to: t(θ) = √(r_m² − r_b² × cos²(θ)).

How do I use the printed saddle cut template?

Print at exactly 100% — never fit to page. Cut out the template rectangle. Wrap it tightly around the branch pipe, aligning the left and right edges at the seam. Tape it securely. Scribe along the curved cut line. Remove the template and cut along the scribed line.

My template is wider than a single A4 sheet — what do I do?

For branch pipes above approximately 60 mm OD, the circumference exceeds A4 width. The tool automatically splits the template across multiple pages with a 15 mm overlap zone and crosshair alignment marks. Print all pages, tape them together matching the crosshairs, then wrap the assembled strip around the pipe.

Can I use this calculator for rectangular hollow sections (RHS or SHS)?

No — this tool is designed exclusively for round pipe (circular section) intersections. RHS, SHS, and other non-circular profiles require a different geometric calculation. For round-to-round pipe joints of any OD from 15 mm to 200 mm and any angle from 15° to 90°, this calculator is accurate.

Pipe Notching & Saddle Cut Calculator

Generate a printable 1:1 saddle cut template for any pipe intersection — instantly, free

OD 15–200 mm Angles 15°–90° PDF Download Metric & Imperial

1 Pipe Dimensions

Main Pipe OD

15–200 mm active

Branch Pipe OD

≤ Main pipe OD

Wall Thickness

For 3D preview only

Scribing Offset

0 = direct scribe

2 Intersection Angle

15° (shallow) 45° 90° (T-joint)

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How to Use This Calculator

The saddle cut formula is: t(θ) = √(r_m² − r_b²·cos²θ) for 90° joints, generalised to t(θ) = [r_b·sin θ·cos α + √(r_m² − r_b²·cos²θ)] / sin α for any angle α. Need the weight of your pipe first? Use our Metal Weight Calculator →

Frequently Asked Questions

Need to calculate the weight of your pipe before cutting it?

Open Metal Weight Calculator →

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