Weld Beam Path Calculator
Enter plate thickness and probe angle to get the half and full skip and the half beam path, place an indication from its sound-path reading, and export the weld cross-section with an inspection record.
Weld cross-section
Single-V · 20.0 mm · 70° probe from the A-side · drawn to scale
- Half skip (SD-H)
- 54.9mm
- Full skip (SD-F)
- 109.9mm
- Half beam path (BP-H)
- 58.5mm
- Full beam path (BP-F)
- 117.0mm
Depth 11.6 mm on leg 1 (BP × cos 70° = 11.6). Surface distance from the index point 31.9 mm, which puts it 4.1 mm on the A-side of the centreline — inside the weld.
| WELD ID : | Inspection date : |
|---|---|
| Job (plate / pipe) | |
| Weld thickness | 20.0 mm |
| Bevel angle | 30° |
| Edge preparation | Single V groove |
| Root face thickness | 2.0 mm |
| Root gap | 2.0 mm |
| Weld configuration | Butt weld |
| Reinforcement | 1.5 mm |
| Welding process | SMAW |
| Total weld length | 400 mm |
| Probe angle | 70° |
| Half beam path (BP-H) | 58.5 mm |
| Half skip distance (SD-H) | 54.9 mm |
| Full beam path (BP-F) | 117.0 mm |
| Full skip distance (SD-F) | 109.9 mm |
| Beam path (indication) | 34.0 mm |
| Probe location (from indication) | 31.9 mm |
| Scanning | A side of the weld |
| Defect type | Slag inclusion |
| Defect location (along weld) | From zero 150 mm to 162 mm |
| Defect length | 12 mm |
| Defect width | 1 mm |
| Defect depth (BP × cos 70°) | 11.6 mm |
| Acceptance criteria | |
| Scanning result | |
| A-scan memory no. |
Step by step
How it works
The same trigonometry you'd do on a calculator before a scan, drawn out so you can see where the beam actually goes.
Set up the weld and probe
Enter the thickness, bevel and probe angle. Skip distances and beam paths update as you type, and the cross-section is redrawn to scale.
Place the indication
Enter where the probe stands and the beam path reading. The defect is plotted on the right leg of the beam, with its depth worked out for you.
Export the record
Download the diagram as PNG or SVG, or save the diagram and the inspection record together as a PDF from your browser's print dialog.
FAQ
Questions, answered
Which formulas does it use?
Half skip is T × tan θ and full skip 2T × tan θ; half beam path is T ÷ cos θ, where T is the thickness and θ the probe angle. Enter a half beam path of your own and the angle is worked back from it: θ = cos⁻¹(T ÷ BP-H). An indication at beam path S sits S × sin θ from the index point. Its depth is S × cos θ on the first leg, and 2T − S × cos θ on the second leg, after the back-wall bounce.
What does probe location mean here?
The distance from the probe's index point to the weld centreline, measured along the scanning surface. Aim at the root sets it to the half skip, so the first leg lands on the root.
Is the drawing to scale?
Yes. Thickness, bevel, root gap, probe position and beam angles are drawn at true proportion. Only the probe, the cap and root bead heights, and the defect marker are drawn at a fixed size, so they stay visible.
Does it replace a calibrated flaw detector or a written procedure?
No. It's a calculator and drawing aid. It assumes a flat plate, a single-V groove, a perfect back-wall reflection, and the exit point and angle you enter. Probe index offset, curvature and acceptance criteria come from your calibration and your procedure.
Is anything uploaded?
No. The calculation and the drawing run in your browser, and the setup is remembered only in this browser so a refresh doesn't lose it.
We make apps too
This tool is a side project of Gigantic Apps — an independent studio whose 14 education and utility apps have been downloaded 12M+ times. Same idea as this page: no accounts, no clutter, free to use.