StubCalcStubCalc Bend / Free calculators
Box offset calculator
A box offset is a small offset, usually about 1/2" at 10°, so the pipe sits flat on the wall and enters the box or fitting straight. Enter where the offset starts and get both marks.
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How a box offset is laid out
It is an ordinary offset with a small rise, measured to the start of the offset. Mark A goes at the distance from the pipe end, mark B at A + between marks. Bend A, roll the pipe 180°, bend B to the same angle.
At 10° the multiplier is 6.0, so a 1/2" rise puts the marks 3" apart. Many electricians bend box offsets by eye; the numbers help when several pipes have to match.
The bender chart rounds 10° to 6.0 where the exact cosecant is 5.76, so the offset comes out a little taller. The result shows how far the methods differ.
More free calculators
The five free bends from StubCalc Bend, right in your browser.
Check marks against your bender; verify with local code. The calculator uses a generic EMT hand bender. Take-up and multipliers differ between makers, so compare with the numbers on your shoe. Not affiliated with NFPA or any bender maker.