Analysis · Verified against Amazon Seller Central, 27 August 2026
Amazon published its own before-and-after comparisons for the 15 January
change. Five products, five different outcomes, ranging from a $0.74 saving to a 51% increase.
What this is. Amazon’s own published figures, collected and read together. No
modelling and no estimates — these are the comparisons Amazon put in its help documentation, which
most sellers never opened.
First, the correction
The widely-repeated version of this story is that Amazon “extended dimensional weight to all major
size tiers in 2026.” That isn’t what happened. Amazon extended dimensional weight to large
standard-size products below 12 ounces in 2022, and to apparel from
16 February 2023. Under the tier definitions in force until 14 January 2026, Amazon
already used dimensional weight for Large standard, oversize, Large Bulky and Extra-Large whenever it
exceeded unit weight.
What actually changed on 15 January 2026:
- The Large Bulky tier split, creating a new Small Bulky tier
- The flat $1.32 SIPP discount on bulky products was removed, replaced by a
packaging fee on non-SIPP bulky units priced by dimensional weight - A new Overmax handling fee of $17–$25
- Low-inventory-level and inbound placement fees now reach bulky products
- A 3.5% fuel and logistics surcharge from 17 April 2026
None of it applies in the UK. There is no equivalent European size-tier change for
2026 — European referral and FBA fees were cut in December 2025 and January 2026. Don’t transplant
the American numbers onto UK SKUs.
The five products, in Amazon’s own figures
| Product | Tier | 2025 | 2026 | Change |
|---|---|---|---|---|
| Vent cover filter 18 × 17.75 × 2.75 in, SIPP |
Small Bulky | $10.31 | $9.57 | −$0.74 |
| Baby cot 24 × 7.5 × 6 in, not SIPP |
Small Bulky | $12.27 | $12.18 | −$0.09 |
| Shoe storage bench 47.5 × 17.25 × 4.38 in, SIPP |
Large Bulky | $17.71 | $18.77 | +$1.06 |
| Book shelf 37.58 × 12.27 × 5.74 in, not SIPP |
Large Bulky | $20.74 | $23.08 | +$2.34 |
| Bulletin board 96 × 48 × 7 in |
Overmax | $33.55 | $50.55 | +51% |
The pattern: products that dropped from Large Bulky into the new Small Bulky tier came out
ahead. Products that stayed Large Bulky paid more, whether or not they were SIPP-enrolled.
And anything crossing 96 inches on its longest side picked up a fee that adds half again to its
fulfilment cost.
The packaging fee, in full
Priced on dimensional weight rather than shipping weight, because dimensions determine
the packaging required. Amazon states it averages $2.07 per unit.
| Dim weight | Fee | Dim weight | Fee |
|---|---|---|---|
| 0–5 lb | $1.51 | 25–30 lb | $3.47 |
| 5–10 lb | $1.68 | 30–35 lb | $3.60 |
| 10–15 lb | $1.97 | 35–40 lb | $3.78 |
| 15–20 lb | $2.60 | 40–45 lb | $3.80 |
| 20–25 lb | $2.92 | 45+ lb | $4.04 |
The 2-inch minimum nobody mentions
For Small Bulky, Large Bulky, Overmax and Extra-Large items, Amazon assumes a 2-inch
minimum on width and height regardless of how flat the product is. Amazon’s own example
makes the point:
A white dry erase board, 40 × 1 × 25 inches, unit weight 4.5 lb. Dimensional weight is
calculated as 40 × 2 × 25 ÷ 139 = 14.4 lb, because the 1-inch
depth rounds up to the 2-inch minimum.
A 4.5 lb board billed as 14.4 lb. Flat products get no reward for being flat once
they’re in a bulky tier — which means shaving depth below two inches buys you nothing there, and
the effort belongs on length and width instead.
What to do this week
- Pull the Fee Preview report and check the tier column. Anything in Small Bulky or
Large Bulky needs looking at. - For every bulky SKU, work out whether SIPP pays. If the packaging fee for your
dimensional band exceeds the cost of SIPP certification, enrol. At $1.51 to $4.04 a unit, that’s
usually a fast decision. - Find the SKUs sitting just over a boundary. Small Bulky caps at 37 inches
longest, 28 median, 20 shortest, 130 length plus girth. An inch of carton redesign moves a product
into a cheaper tier permanently. - Check the 96-inch line. Overmax is the most punitive change of the year.
- Re-run break-even ACoS. A $2.34 increase on a $40 product takes about six points
off your break-even. Campaigns that were profitable in December may not be now, and nothing in
Seller Central will tell you.
We re-tier catalogues for a living
Our audit maps every SKU against the 2026 tier boundaries, models the SIPP decision per product,
and flags the ones where a packaging change pays for itself.
Prepared by Ecom Enable. All figures are Amazon’s own published comparisons and
rate cards, verified 27 August 2026. US marketplace only. Amazon revises its fee schedule each
January and peak rates apply from 15 October.