How to set shipping rate rules (DIM factor, fallback dimensions, surcharges)

Important note: These are global settings that affect the entire shipping system. Want to define rules once and use them everywhere? Set them in this step.

Just want to define values case-by-case instead? You can skip this and configure directly in each Carrier Method under the How to set up carrier methods step – ideal if your carriers follow different rules.

A. Set the DIM Factor

DIM Factor = the number used to calculate Dimensional Weight.

Formula: DW = (Length × Width × Height) / DIM

Steps

#1. Go to Settings → Shipping rate calculator

#2. Enter a number (e.g., 6000)

#3. Save

#4. If you already have carrier methods, choose whether to apply this new DIM globally

For example:

Box size: 40 x 30 x 30 cm
DW = 40 x 30 x 30 ÷ 6000 = 6kg
If the actual weight is 3kg → the carrier charges 6kg, not 3kg.

B. Set fallback dimensions

Fallback dimensions are only used when a product has no size or weight data from:

Shopify product info, and
Product Dimension Rules (we showed you how above)

If either source provides valid dimensions, the fallback will be ignored.

You can use this setting as a safety net to prevent missing data and calculate exact shipping rates.

Steps

#1. Go to Settings → Shipping rate calculator

#2. Turn ON Fallback dimensions

#3. Enter default Length, Width, Height, Weight

#4. Click Save

If a new product hasn’t been updated with size info:

→ The app will use the fallback size (e.g., 20 × 20 × 10 cm)
→ Shipping fee will still calculate correctly, avoiding errors at checkout.

C. Create and manage surcharge types

Surcharges help you add extra fees like:

Fuel charge
Oversize fee
Residential delivery fee

Steps

#1. Go to Settings → Shipping rate calculator

#2. Scroll to Surcharge settings

#3. Click Add surcharge

#4. Name the surcharge (e.g., “Fuel Fee”)

#5. Enter an amount

#6. Save

These surcharges can now be added to any Carrier Method.