USPS Dimensional Weight Calculator
The July 12, 2026 price change tightened the dimensional divisor from 166 to 139. Enter a box you actually ship and see which price tier it lands in under each one.
- 166Divisor before July 12, 2026
- 139Divisor in force now
- 1728 cu inOne cubic foot, the line it applies above
18 × 12 × 12 in = 2,592 cu in, ÷ 139 = 18.65, rounded up to 19 lb.
Priced against the published USPS Ground Advantage commercial table effective October 4, 2026. Dimensional weight applies only above one cubic foot (1728 cubic inches).
Post Office retail is the price USPS publishes for the same billable weight and zone (USPS Notice 123, effective October 4, 2026). I'd Ship That Pro prices, merchant rate card of October 30, 2026. Every I'd Ship That and in-app price on this page is a Pro price. Prices marked Pro price are what Pro members pay. On the free Starter plan, each label adds a platform fee of about 10% of the postage, rounded to the nearest $0.25, at least $0.50 and at most $2.50. Prices shown are for paying from your I'd Ship That balance; paying by card costs slightly more.
The USPS prices on this page are USPS's temporary holiday prices, in effect from October 4, 2026 until January 17, 2027. The I'd Ship That prices on this page are the ones the app shows on its current rate card; USPS's holiday increase does not add to them. See all 2026 USPS price changes.
On This Page
Why a divisor change is harder to spot than a price increase#
A published increase moves the number in the cell. A divisor change moves which cell you read. The box on your bench is identical, the scale reads the same, and the price table can even be flat, but a parcel over one cubic foot now converts to a heavier billable weight, so it prices off a higher row. That is why an average increase quoted as a single percentage rarely matches what a shipper of bulky, light goods actually sees.
The effect is concentrated: it only touches packages over one cubic foot, and within those it hits low-density parcels hardest. Apparel, foam, pillows, assembled plastics and anything shipped with generous void fill move the most. Dense goods in tight boxes often see no change at all, because their actual weight was already the greater of the two.
Three ways to change the answer#
-
Right-size the box.
Volume is the whole input on the dimensional side. Removing two inches from the longest side of a 20 by 12 by 12 box drops it under 2,600 cubic inches, and the billable weight falls with it.
-
Check the cubic-foot line specifically.
A box at 1,700 cubic inches is not subject to dimensional weight; the same contents repacked into 1,800 cubic inches is. It is worth knowing which of your cartons sit just above the line.
-
Price the parcel you are actually shipping.
Declared dimensions that do not match the carton get corrected by the carrier after the fact, and the correction arrives weeks later as an adjustment rather than at purchase.
See this across every package you ship#
I'd Ship That prices your own shipping history against a rate change and shows which services, zones and box sizes move, before the new prices take effect.
Create a labelFrequently asked questions#
What is dimensional weight?#
Dimensional weight prices a package by the space it occupies instead of what it weighs. USPS divides the box volume in cubic inches by a fixed divisor to get a weight in pounds, then bills whichever is greater: that number or the actual weight. It only applies to packages over one cubic foot (1728 cubic inches).
What changed on July 12, 2026?#
The divisor dropped from 166 to 139. A smaller divisor produces a larger dimensional weight from the same box, so a parcel that has not changed at all can land in a heavier price tier than it did before. Packages under one cubic foot are unaffected.
Does dimensional weight apply to flat rate packaging?#
No. Flat rate pricing is set by the container, not by weight or volume, so the divisor does not enter into it. Dimensional weight applies when you supply your own box and the parcel exceeds one cubic foot.
How do I find my zone?#
Zone is the distance band between the origin ZIP code and the destination ZIP code, from Zone 1 (local) to Zone 9. The same box costs more the further it travels, which is why the calculator asks for it separately from size and weight.