Okay, for a quick rule of thumb for box offsets in EMT, it's best to think about it in terms of offset depth.

Rule of Thumb



Add roughly twice the offset depth for each offset.Example

Let's say your boxes are offset by 4 inches. That means a 4" offset is needed. You have two offsets, so total compensation would be roughly: 2(24") = 16".

Therefore, for a 15-foot (180-inch) run with two 4" box offsets, you would add roughly 16 inches, making your total EMT length approximately 196 inches (16'4").Important Considerations


Bender Type

This is a very generalized rule of thumb. Different benders (hand benders vs. hydraulic benders) may produce slightly different shrinkage amounts.2.

Offset Depth

The deeper the offset, the more length you'll need to add.3.

Accuracy

For critical runs, or if you're trying to minimize waste, it's always best to make a test bend or refer to the specific bender's chart. The bender chart will give you the take up on each bender.4.

Experience

After doing a few bends, you'll develop a better feel for how your specific bender behaves.

In summary: This "twice the offset depth per offset" rule is a decent starting point for a quick estimation, but always prioritize accuracy when it matters. Flag for review