Does the surcharge count all items or only heavy ones?

Your choice. A cart fee charges the whole cart's weight once the threshold passes; a per-product fee charges only matching items' weight, for example only products in the Furniture collection.

Can I cap the surcharge?

Yes, weight-based fees accept a maximum, for example never more than 49.00, so extreme orders stay reasonable.

What about oversized but light items?

Tag them oversized and use a fixed per-product fee instead; weight is not the only trigger available.

Heavy & oversized item surcharges on Shopify

Last updated: July 18, 2026

Carriers charge you dearly for heavy and bulky shipments. On Shopify, recover it with a per-kilogram cart fee gated by a cart weight condition (for example, 0.80 per kg once the cart reaches 20 kg), or a per-product weight fee that charges only bulky items. Light orders pay nothing; heavy orders pay in proportion.

The rule in FlexiFees

Setting	Value
Fee title	Heavy order surcharge
Calculation	Per kilogram, cart fee
Amount	0.80 per kg (with an optional maximum cap)
SKU	HEAVY
Condition	Cart weight is greater than or equal to 20

FlexiFees condition builder with cart weight at least 20 kg

Variants of the pattern

Only bulky products: a per-product weight fee with a collection or tag condition charges furniture by its weight while accessories stay free.
Flat oversized fee: a fixed per-product fee on tag oversized for items that are big rather than heavy.
Title conventions: if titles already contain OVERSIZED, the product title condition needs no retagging.
Cap it: a maximum (say 49.00) keeps extreme orders friendly. How caps work.

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Heavy & oversized item surcharges on Shopify

The rule in FlexiFees

Variants of the pattern

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