To charge less for light orders, add the condition Cart weight Is at most 500 g and set your Standard rate to Fixed Price 4. Carts of 500 g or less pay $4 for Standard, and heavier carts pay your normal rates. Shopify’s own free shipping discount has no weight condition and can only make shipping free, not set a price. RM: Advanced Free Shipping checks the cart weight in g, kg, oz or lb at checkout and discounts the rates you already have, flat or carrier-calculated. It costs $9.90 USD every 30 days, with a 7-day free trial, billed by Shopify.

What the customer gets

In this example the store sells socks at $12.50 a pair, each weighing 100 g. The rates are Standard $8.90 and Express $24.90.

  • Two pairs ($25, 200 g): under 500 g, so the cart qualifies. Standard drops from $8.90 to $4. The customer pays $25 + $4 = $29. Express stays $24.90.
  • Five pairs ($62.50, 500 g): exactly 500 g still qualifies, because the operator is Is at most. The customer pays $62.50 + $4 = $66.50.
  • A 1.2 kg hoodie order ($60): over 500 g, so nothing changes. With Standard, the customer pays $60 + $8.90 = $68.90.

The weight is each product’s weight in Shopify, times the quantity.

Set it up

  1. In the app, click Create Shipping Discount.
  2. Under Discount method, choose Automatic discount. New discounts start on Discount code, and the method can’t be changed later. Enter a Title such as “$4 shipping on small orders”. Customers see it at checkout.
  3. In Conditions, click Add condition and choose Cart weight. Set the operator to Is at most.
  4. Leave the unit on g (grams), the default, and enter 500.
  5. In Discount setup, set Delivery type to Shipping and Which rates to Choose specific rates. Select Standard from the list.
  6. Set Discount value to Fixed Price and enter 4.
  7. Click Create discount.

Discount setup with Delivery type Shipping, Which rates set to Choose specific rates, the Standard rate selected, and Discount value Free

The screenshot shows Free. Choose Fixed Price in step 6 to set a price instead.

How Fixed Price works

Fixed Price sets the rate to exactly the amount you enter, and only ever lowers it. In this example:

  • Standard at $8.90 becomes $4.
  • A carrier rate that comes back at $3.60 for a tiny parcel stays $3.60. Fixed Price never raises a rate.

With live carrier-calculated rates, the price changes with weight and distance, so a $4 cap gives light orders a predictable price.

Variations

  • Free shipping on light orders: set Discount value to Free. Two pairs of socks cost $25 in total.
  • US units: choose lb and enter 1 (about 454 g). Products weighed in grams or kilograms are converted to the unit you pick.
  • Light orders over $20 only: add Cart total Is at least 20 in the same rule group. Both must pass.
  • The cheapest rate instead of Standard by name: set Which rates to Cheapest shipping rate. This works well with carrier rates whose names vary.
  • Light orders, or any cart over $100 free: create a second discount with Cart total Is at least 100 and Free. If a cart qualifies for both, Shopify gives the customer the one that saves the most.
  • $2 off instead of a set price: use Fixed Amount Off 2. Standard becomes $6.90.

Good to know

  • To count every product, give every product a weight in Shopify. Products with no weight count as 0, so a cart of unweighed items passes “Is at most 500 g”.
  • To get the unit right, pick it before you type the number. 500 g and 500 kg are very different carts.
  • To keep this in one country, add Shipping country Is one of in the same rule group.
  • To make the cheapest rate work, remove any $0 rate from Settings → Shipping and delivery. A $0 rate counts as the cheapest.
  • To test it, turn on Test mode and check out with the shipping first name ABC123, with a cart just under and just over 500 g.

Install RM: Advanced Free Shipping from the Shopify App Store.