How to measure a box for shipping
Ordering the wrong box size is one of the most common and expensive packaging mistakes. A box that's too small won't close. A box that's too large needs extra fill and costs more to ship. Most of these errors come from two things: measuring in the wrong order, or measuring the wrong side of the board.
The order: length × width × height
Box dimensions are always written as length × width × height (height is also called depth). This is an industry convention, and suppliers read your numbers in that order whether you intend it or not.
- Length is the longer side of the opening, when you look down into the box from the top.
- Width is the shorter side of the opening.
- Height is the distance from the opening to the bottom.
So a 12 × 6 × 10 box has a 12 × 6 opening and stands 10 tall. A 12 × 10 × 6 box has the same volume but a wide 12 × 10 opening and is only 6 tall. They are very different boxes, which is why the order matters.
How to measure an existing box
- Open the box and look inside. Measure the inside unless you have a reason not to. Suppliers quote inside dimensions.
- Measure the length. Along the longer side of the opening, from one inside wall to the other.
- Measure the width. Along the shorter side of the opening, again wall to wall.
- Measure the height. From the inside of the bottom flaps up to the top of the side wall, not including the top flaps.
- Write it down in order. Length × width × height, with units. Round to the nearest 1/8 inch or millimeter.
If you're measuring for a carrier label or a shipping quote, do the same thing on the outside of the closed box, including any bulge from overfilling.
How to measure a product for a new box
When you're sizing a box around a product, measure the product rather than guessing from an old box.
- Measure at the widest point on each side, including handles, pumps, caps, cables and hang tags.
- If the product sits in a retail box or bag, measure that, because that's what goes into the shipper.
- For irregular shapes, measure the smallest rectangle the item fits inside.
- For multiple items packed together, arrange them as you'll pack them and measure the whole group.
Then add cushioning to each side. Entering the product size into the box size calculator does that step for you and gives the inside dimensions to order.
Common measuring mistakes
Measuring outside and ordering by it
If you measure the outside of your current box and order that as an inside size, the new box will be slightly bigger every time. Over thousands of shipments that adds up in fill and dimensional weight.
Swapping width and height
This is the most common error. It gives you a box with the right volume but the wrong opening, and the product often won't go in the way you pack it.
Forgetting the cushioning is on both sides
One inch of cushioning means one inch on each side, so the box needs to be two inches bigger in each dimension, not one.
Rounding down
If a product measures 9⅝ inches, a 9½ inch box will not work. Always round up when converting product sizes into box sizes.
Measuring for mailers and other box styles
The same length × width × height order applies to mailer boxes, tuck-end boxes and most folding cartons. For tuck-end cartons, the opening is at the end, so length and width describe the end panel and height (depth) is the long side. If you're not sure how a supplier reads dimensions for a particular style, send them a quick sketch with each side labeled.