Parcel planning · Shipping
Compare actual and volumetric weight
Your scale says 11 pounds. The carrier might bill 17. Both numbers can be correct, because one describes mass and the other describes the space that mass occupies. Record the inputs and the gap stops being a surprise.
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Three weights, one parcel
Actual weight is the packed parcel on a scale. Volumetric (dimensional) weight is a space proxy: length × width × height divided by a carrier divisor. Billable weight is whichever of the two the carrier's rule selects, usually the greater.
The divisor is not universal. Rate cards publish different divisors for different services and units, and some apply a minimum. That is why "my box is 22 inches long" alone tells you nothing about the charge.
Inputs you must record
- Packed weight, measured after taping — not the product's listed weight
- Outer length, width, and height in inches or centimeters, with the unit written in the header
- The divisor you used, and which service it belongs to
- The date of measurement, since repacking changes everything
- Whether the box bulges: carriers may measure the widest point
If you cannot fill the divisor field, stop there. Writing a plausible divisor is worse than leaving it blank, because it makes a guess look like a rate.
A labeled example calculation
Assume a parcel measuring 20 × 14 × 10 in with an actual weight of 11.0 lb, and a hypothetical divisor of 139 in³/lb from a rate card you have in front of you.
| Step | Operation | Result |
|---|---|---|
| Volume | 20 × 14 × 10 | 2,800 in³ |
| Volumetric weight | 2,800 ÷ 139 | ≈ 20.1 lb |
| Actual weight | Scale reading | 11.0 lb |
| Billable weight | max(11.0, 20.1) | ≈ 20.1 lb |
The gap here is almost 9 lb, and it exists because the box is large for its contents. If the same items fit a 16 × 12 × 8 in box, the volume falls to 1,536 in³ and volumetric weight to about 11.1 lb — nearly level with the scale. The saving, if any, depends on the rate card you are actually using, not on this example.
Test this with your own numbers in the estimate tool. Change only the dimensions and watch the billable weight move; that sensitivity is the real lesson.
Bringing the two numbers closer
Two levers exist: reduce volume or accept the dimensional charge. Reducing volume means removing a shoebox that is mostly air, folding instead of rolling, or choosing a box that fits the largest item rather than the first box within reach. Each choice trades protection for space, and that trade belongs in the record.
The packing options guide covers how to log that decision, and the quote record guide explains which quoted fields the calculation depends on. If the parcel is near a carrier's oversize threshold, note the threshold source and date; those limits are revised.
Finally, keep both numbers in the row after the parcel ships. When the invoice arrives, you can compare billable weight against the carrier's stated figure. That is the only way to learn which divisor actually applied to your route.
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