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How to Measure a Box

This is a Regular Slotted Container (RSC). A carton like this can typically be run without the need for additional tooling. Aside from the inside dimensions, an RSC is made up of a body and major/minor flaps.

The flap length of an RSC is determined by the width panel. The major flaps run the length of the carton, and are cut to 1/2 of the width. The minor flaps are cut at the same point.

If a carton is a square (10 x 10 x 10), then the minor and major flaps will meet in the middle, creating a solid “floor”.

If a carton is not a square (10 x 6 x 10), then the minor flaps will extend to 1/2 of the width, while the major flaps meet in the center.

This comes into play when measuring a carton, as there is a variety of ways to measure it, but only one correct way to determine the true internal dimensions.

When a carton is measured from the outside, there are several factors that cause it to grow beyond the internal dimensions. In this example, C-flute has a thickness of 3/16”, and there are 4 thicknesses of board built up.

Where an outside dimension may be measured at 10 5/8”, the true inside dimension would be 10”. As seen in this example, there is an additional depth of 10 1/4”. This is due to the fact that this RSC doesn’t have a solid bottom, meaning it has a partial true depth of 10”, and a partial false depth of 10 1/4”.

If a carton is measured while erected, opening the top flaps for inside dimensions, a false depth could be recorded. This is because the minor panels are not being measured as part of the box depth, or the carton does not have a solid floor.

For BC Flute, this could mean a difference of 3/4” between the measured depth and true depth.

What is the best way to measure for true I.D.?

While a rough estimate can be determined by measuring an erected carton, the best way to find the inside dimension is to open the carton and measure the score to score dimension. Some customers prefer to measure from the 0" mark of a tape measure, but due to the inconsistency that can come with marker, we typically recommend measuring from the 1" mark. This way you can simply remove the inch at the end and have a more accurate measurement.

With this information in hand, we can help you convert a score to score measurement to an internal dimension by adding in the allowances that come from outside gain/inside loss.

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