What is the Amazon FBA Dimensional Weight formula in 2026?

For US FBA sellers, Dimensional Weight (lbs) = (Length × Width × Height in inches) ÷ 139. For Canada, UK, and Europe, Dimensional Weight (kg) = (Length × Width × Height in centimeters) ÷ 5000.

When does Amazon charge Dimensional Weight instead of Actual Weight?

Amazon charges the greater of unit actual weight or dimensional weight for all Large Standard-Size units (weighing more than 0.75 lb) and all Oversize units (Small Oversize, Medium Oversize, and Large Oversize).

How is Length + Girth calculated for Amazon Oversize packages?

Girth is equal to 2 × (Width + Height). Length + Girth is therefore calculated as: Longest Side + 2 × (Median Side + Shortest Side). Standard-size units must have Length + Girth of 130 inches or less.

What are the dimensions for Large Standard vs Small Oversize?

A Large Standard unit has a maximum longest side of 18 inches, median side of 14 inches, shortest side of 8 inches, and actual weight of 20 lbs. If any single dimension exceeds these thresholds, the product automatically escalates to the Oversize tier, resulting in significantly higher fulfillment fees.

2026 Amazon FBA Divisor 139 • US, CA, UK & EU Standards

Amazon FBA Dimensional Weight & Size Tier Checker

Enter packaged product dimensions to determine your billable shipping weight, size classification tier, estimated base fulfillment fee, and package optimization savings.

1. Marketplace & Measurement Units

Step 1 of 3

Marketplace Region

Measurement System

2. Packaged Item Dimensions & Weight

Step 2 of 3

Length (in) Longest side

Width (in) Median side

Height (in) Shortest side (thickness)

Actual Packaged Weight (lbs) Item + packaging scale weight

Product Category

Quick Product Presets

Large Standard-Size

Amazon Billable Weight

3.24 lbs

Charged by Dimensional Weight (Exceeds Actual by +1.44 lbs)

Actual Weight 1.80 lbs

Dimensional Weight 3.24 lbs

Unit Volume: 450.00 in³ (0.26 ft³)

Length + Girth ($L + 2W + 2H$): 38.50 in

DIM Divisor Used: 139 (US Standard)

Est. Base FBA Fulfillment Fee: $6.10 / unit

Est. Monthly Storage (Jan–Sep): $0.20 / unit / mo

Est. Q4 Peak Storage (Oct–Dec): $0.62 / unit / mo

Packaging Optimization Insight

Your dimensional weight is driving your fulfillment fee. Reducing package dimensions by just 1 inch saves billable weight on every unit shipped.

Amazon FBA Size Tier Classification & Fee Standards (2026)

Master the strict dimension limits, dimensional divisor formulas, and weight thresholds that dictate Amazon Fulfillment charges.

Amazon FBA Size Tier Thresholds Matrix (US Imperial)

Size Tier	Max Weight	Longest Side	Median Side	Shortest Side	Length + Girth
Small Standard	16 oz (1 lb)	≤ 15"	≤ 12"	≤ 0.75"	—
Large Standard	20 lbs	≤ 18"	≤ 14"	≤ 8"	—
Small Oversize	70 lbs	≤ 60"	≤ 30"	—	≤ 130"
Medium Oversize	150 lbs	≤ 108"	—	—	≤ 130"
Large Oversize	150 lbs	≤ 108"	—	—	≤ 165"

The 0.75-Inch Thickness Cliff

If a product's thickness exceeds 0.75 inches, even by 0.05 inches, it immediately jumps from Small Standard to Large Standard, triggering a steep jump in fulfillment base fees. Vacuum sealing and custom cardboard sleeves can keep your product in the lowest fee bracket.

Why Divisor 139 Matters

Commercial carriers (FedEx/UPS retail) frequently use a 166 divisor, but Amazon enforces the aggressive 139 divisor for US fulfillment. A lightweight pillow or bulky jacket measuring 18" × 14" × 6" yields a dimensional weight of $(18 \times 14 \times 6) / 139 = 10.88\text{ lbs}$, even if it only weighs 1 lb.