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Calculate bend marks for offsets, three-point saddles, four-point saddles, 90-degree stubs, and back-to-back 90s. The calculator stays first; the reference chart and examples are below it.
Mark spacing uses M = 1 / sin(θ). The shrink values are common field approximations, not exact allowances for every bender.
| Angle | Multiplier | Field shrink per unit of rise |
|---|---|---|
| 10° | 5.76 | 1/16 (0.0625) |
| 15° | 3.86 | 1/8 (0.125) |
| 22.5° | 2.61 | 3/16 (0.1875) |
| 30° | 2.00 | 1/4 (0.25) |
| 45° | 1.41 | 3/8 (0.375) |
| 60° | 1.15 | 1/2 (0.50) |
Enter the finished dimensions and select Calculate bend marks.
The diagram automatically scales to the calculated marks. Use the result table for the exact values.
Hold the phone's long edge parallel to the conduit, calibrate it on a known level reference, then compare the reading. Sensor and browser behavior varies.
Use a level or calibrated angle tool for critical work.
The calculator uses the common rounded mark-spacing multipliers shown below. They approximate the ideal point-bend relationship M = 1 / sin(θ). Field shrink constants are quick-layout conventions and can differ from geometric values and actual bender results.
| Offset angle | Mark-spacing multiplier | Approximate field shrink per unit of rise | Typical use note |
|---|---|---|---|
| 10° | 5.76 | 1/16 (0.0625) | Long, gradual offset |
| 15° | 3.86 | 1/8 (0.125) | Gradual offset with less run than 10° |
| 22.5° | 2.61 | 3/16 (0.1875) | Common outer angle for a three-point saddle |
| 30° | 2.00 | 1/4 (0.25) | Simple mental math for many offsets |
| 45° | 1.41 | 3/8 (0.375) | Shorter offset with sharper bends |
| 60° | 1.15 | 1/2 (0.50) | Very compact layout; verify bend and pull requirements |
Metric note: multiply a rise in millimeters by the same multiplier or shrink ratio to receive millimeters. Do not divide a dimensionless shrink ratio by 25.4.
For a 5-inch rise using 30° bends, the rounded multiplier is 2.00:
5 in × 2.00 = 10 in between marks
The common field-shrink estimate is 5 × 1/4, or 1.25 inches. How that estimate is applied depends on the reference mark and finished layout.
For a 4-inch-high saddle with 22.5° outer bends, place the center bend 10.44 inches from each outer mark:
4 in × 2.61 = 10.44 in
The center bend target is 45°. Verify where the saddle center must land before choosing the first outer mark.
For a 4-inch rise, 6-inch obstacle width plus clearance, and 30° bends, the idealized intervals are:
8 in, then 6 in, then 8 in
The two offset sections have a combined field-shrink estimate of about 2 inches before bender-specific adjustment.
For an 18-inch finished stub with a verified 5-inch deduct:
18 in - 5 in = 13 in arrow/start mark
Align the correct start-of-bend mark specified for that bender. Do not assume every bender or conduit size uses the same deduct.
The mark-spacing multiplier is the cosecant of the bend angle: 1 / sin(θ). Common rounded values are 2.00 for 30°, 2.61 for 22.5°, and 1.41 for 45°.
No. They are common field approximations. Actual shrink varies with bend radius, conduit material and size, bender, and technique. Verify critical layouts with the exact equipment and a test bend.
For a typical hand-bender arrow method, subtract the verified bender deduct from the desired finished stub height. Confirm the correct reference mark and deduct for the exact bender and conduit size.
It displays two back-of-bend reference marks separated by the finished distance you enter. Use the manufacturer-specified star or back-of-90 reference where applicable. It does not infer parallel-leg spacing from an unknown bend radius.
No. It is a layout aid. It does not evaluate code compliance, conductor-pulling limits, jobsite conditions, or manufacturer requirements.
Phone sensor readings vary by device, browser, screen orientation, placement, and calibration. Treat the feature as an approximate check, not a replacement for a level or calibrated angle tool.
The trigonometric spacing formula is an idealized point-bend model. The field shrink constants are conventional approximations and should be reviewed by an experienced electrician or instructor before publication as instructional guidance.