How to measure package dimensions and weight

Every rate you see in Octoship is calculated from two things: how heavy your package is and how big it is. Get either one wrong and the carrier will notice — their sorting machines weigh and scan nearly every parcel — and you'll see an adjustment charge a few weeks later. The good news: measuring correctly takes about thirty seconds once you know the rules.

What you'll need#

• A digital shipping scale that reads in ounces (or tenths of an ounce). Kitchen scales work for small parcels; a 50–100 lb postal scale is worth it once you ship daily.
• A rigid tape measure or ruler. Soft sewing tapes stretch and curve, which makes boxes look smaller than they are.
• Your package fully packed and sealed — tape, padding, packing slip and all.

Measuring step by step#

1. 1
   Zero your scale

   Turn the scale on with nothing on it (or press Tare) so it reads 0. If you weigh on a tray or bin, tare with the tray on.

2. 2
   Weigh the sealed package

   Set it in the middle of the platform and wait for the reading to settle. Enter pounds and ounces separately in Octoship — 1 lb 3 oz, not 1.3 lb.

3. 3
   Measure the length

   Length is always the longest side. Measure edge to edge across the widest point, including any bulges from overstuffing.

4. 4
   Measure width and height

   Width and height are the two remaining sides, measured perpendicular to the length. For soft mailers, lay the package flat and measure at its thickest point.

5. 5
   Save it as a package preset

   If you use the same box regularly, save the dimensions under Settings → Packages so they auto-fill next time. Weight still needs to be entered per shipment.

Screenshot

How rounding works#

Carriers don't price on fractions, so Octoship rounds the way they do. You don't need to round yourself — enter what your scale and tape say — but knowing the rules explains why a tiny change can bump your rate.

So a package weighing 15.2 oz ships as 16 oz with USPS, and a package weighing 1 lb 0.4 oz ships as 2 lb. If you're hovering just over a line, a lighter mailer or a few fewer packing peanuts can save real money.

Dimensional weight, explained#

Big, light boxes take up space on a truck without adding much weight, so carriers charge for whichever is greater: the actual weight or the dimensional (dim) weight. Dim weight is calculated by multiplying length × width × height and dividing by a carrier-specific divisor.

• USPS: dim weight applies only when the package is larger than 1 cubic foot (1,728 cubic inches). Divisor: 166.
• UPS and FedEx: dim weight can apply to any package size. Divisor: 139 for most commercial rates.
• DHL Express: dim weight applies to every international shipment. Divisor: 139 in inches and pounds (5000 in centimeters and kilograms).

Example: a 14 × 12 × 10 in box holding a 3 lb pillow. That's 1,680 cubic inches, just under 1 cubic foot, so USPS bills the actual 3 lb. UPS and FedEx divide 1,680 by 139 for a dim weight of 12.09 — rounded up to 13 lb, which is what you'd pay for. Octoship shows the billable weight next to each rate so there are no surprises.

Common mistakes that trigger adjustments#

• Reusing a preset for a box that got stuffed and now bulges.
• Entering product weight from a listing instead of weighing the packed box.
• Typing 1.5 meaning 1 lb 5 oz (it's actually 1 lb 8 oz).
• Forgetting that soft mailers have a height — a padded envelope with a hoodie inside is a parcel, not a letter.

If a carrier does adjust a label, you'll see it on your billing history with the measurements they recorded. Measuring carefully up front is the cheapest insurance there is.