Tube Bend Calculator
Eleven bend calculations for instrument techs, pipefitters, and conduit workers. Offset, rolling offset, saddle bends, arc length, gain, back to zero, and more — with fractional output for any denomination.
Inch inputs accept decimals 6.5 or fractions 6-5/8 · 5/8 · 6 5/8
How tube bend math works
Every tube bend calculation reduces to the same three ingredients: an angle, a radius, and a measurement of where you are in space. The formulas change depending on what you know and what you're solving for — which is why having all eleven modes in one place matters.
Offset & Bend Loss
A two-bend offset steps around an obstacle while keeping the tube parallel. You need rise, bend angle, and travel — any two determine the third. Bend loss is subtracted from your layout to account for the arc consuming more length than a straight corner would. On a 45° offset with a 6" rise, loss is about 2.5".
Rolling Offset
Moves the tube in two directions at once — vertical and horizontal — with a single pair of bends. The key output is the roll angle: how far you rotate the tube around its axis before bending. Set it correctly and both offsets resolve simultaneously. The true offset drives the travel calculation.
3-Point Saddle
Steps over a round obstacle like a pipe or conduit. The center bend is exactly double the two outside bends. Spread is the distance from the center mark to each side mark. A 45° side angle is common — it works with most hand benders without exceeding bend capacity.
4-Point Saddle
Steps over a rectangular obstacle like a beam, box, or duct. Four equal bends create a flat-topped bridge. The leg travel is the diagonal of each outside section; the flat top spans the obstacle width exactly.
Arc Length
The distance along the tube's centerline through the bend — also the stop point on the bender scale. This is what you read off the bender when making a precise stop. Not the straight-line distance; the actual path the centerline travels through the arc.
Gain
The difference between the tangent projection through a corner and the shorter arc. On a 90° bend at 1.5" CLR, gain is ~0.43". On multi-bend pieces, accumulated gain affects where the far end lands — six 90° bends at 1.5" CLR adds up to about 2.6" if you don't account for it.
Back to Zero (B2Z)
The distance from your next bend mark back to the bender's zero reference. Knowing B2Z lets you position the tube correctly for each successive mark on a multi-bend piece without remeasuring from a new datum each time.
Equal Spread
The mark spacing for a bank of parallel tubes making identical offsets. Get it right and all tubes come out parallel and dressed. Get it wrong and the run looks like a staircase. Critical on instrument tube bundles and conduit banks.
Reverse Bend
A reverse bend changes direction opposite to the previous bend — used when a run needs to jog back toward its original centerline. Enter your offset rise and angle; the calculator gives you travel and loss so your marks land correctly on both bends.
Sloped Tubing
Calculates the bend angle and total rise for any run with a required minimum slope — drain lines, instrument sample lines, or any tube that must maintain a grade. Enter slope in inches per foot (1/4"/ft is typical for instrument drains) and run length.
Figure Degree
Calculates the sine, cosine, and tangent of any bend angle — the raw trig values that drive every other formula on this page. Useful when you're working a custom angle that isn't in your head and need to verify a multiplier before committing marks to tube.