Built for logistics
Respect your carrier's weight limits
Prime MOQ sets a minimum and a maximum total cart weight, read from the weights already on your products. A Shopify Function checks the cart against that band at checkout, so an order the carrier would refuse never reaches the warehouse.
A tile store ships heavy goods. Their parcel carrier refuses anything over 100 lb, and a pallet only makes financial sense above 10 lb.
Orders outside that band are discovered in the warehouse, not at checkout: the label fails to print, the customer is called, and the order is rebooked or refunded.
A weight band on the cart moves that conversation to the product page, where a Contact us button turns an oversized order into a freight quote.
The rule
Cart weight between 10 lb and 100 lb
- Limit type
- Weight
- Scope
- Entire cart
- Minimum
- 10 lb
- Maximum
- 100 lb
- Unit
- lb, oz, kg or g
In the app this is the Weight limitsquick-start template, already filled in.
Wholesale Green Tea 50g
$12.50 - per unit, 0.5 lb
110.0 lb in cart
For bulk orders, please click Contact us
Live demo - this is exactly what your customers see.
- Included
No failed labels or rebooked shipments from carts the carrier will not take.
- Included
Weight is read from your product data, so nothing extra to maintain.
- Included
Oversized carts become freight conversations instead of refunds.
Merchant profile
A tile and stone merchant selling to builders, renovators and interior fitters. Almost everything in the catalogue is heavy, and the weight of an order decides which carrier can take it long before price enters the conversation.
Two shipping lanes exist side by side: a parcel carrier for anything a courier can lift, and a pallet booking for the rest. Each lane has a band it works inside, and orders outside both bands have no lane at all.
The challenge
Shopify will happily accept a cart no carrier will take. The order is confirmed, the payment is captured, and the problem is discovered when a label refuses to print.
At that point the options are all bad. Split the shipment and lose the margin, rebook onto a pallet the customer did not pay for, or call and refund, which means the sale is gone and the goodwill with it.
What they needed
- Catch an unshippable cart at checkout rather than in the warehouse, where every option costs money.
- Enforce a band rather than a ceiling, because the low end is a commercial problem even though nothing physically fails.
- Give oversized orders somewhere to go, since those are the largest carts in the store and refusing them outright is the worst outcome.
Why it costs money
A failed label is not one cost, it is a chain: the picked order sitting in the bay, the phone call, the rebooking at a rate nobody quoted, and the slot lost on a courier collection that was already paid for.
The low end costs money differently. A pallet booking costs nearly the same whether it carries very little or a great deal, so an order that is technically shippable can still be sold at a loss because it went down a lane priced for volume it never had.
Approaches that fail
Putting the weight limit in the shipping policy page
A policy page is not consulted while a cart is being built. The buyer who overloads a cart is usually the buyer moving fastest, and they will read the policy only after the refund email explains where it was.
Relying on carrier-calculated rates to refuse the order
Rate calculation answers how much, not whether. A cart that exceeds a service limit often returns a rate anyway, or returns none and silently falls back to a flat rate, which is worse because the order proceeds.
Capping quantity per product instead of weight
Quantity is a poor proxy when a catalogue mixes weights. Ten boxes of mosaic and ten slabs of stone are the same quantity and nothing like the same freight problem, so a quantity cap is either useless or punitive.
Weighing the options
| Approach | Stops the bad cart | Understands mixed carts | Rescues the large order |
|---|---|---|---|
| A note in the shipping policy | No, nothing is enforced | Not applicable | No, the buyer simply leaves |
| Carrier-calculated rates | Unreliably, it may return a rate | Partly, it sums the cart | No, there is no next step |
| A cart weight band | Yes, at checkout | Yes, it sums real product weights | Yes, through a freight enquiry |
The rule they chose
A weight band on the whole cart, with both a floor and a ceiling, read from the weights already recorded on the products. Using existing product data rather than a separate table is the part that keeps it honest: there is no second source to fall out of step.
Above the ceiling the cart is held and offered a Contact us route, because an oversized order is a freight conversation rather than a lost sale. Below the floor the buyer is told what the minimum is, which usually results in a larger cart rather than no cart.
What the buyer sees
The band is expressed in the unit the catalogue already uses, so a buyer never has to convert anything to understand why a cart was refused.
The message names the limit and offers the next step in the same breath. For the heaviest carts that next step is an enquiry, which is how the biggest orders in the store stay in the building.
What could go wrong
- RiskA variant with no recorded weight makes a heavy cart look light
- MitigationAudit product weights before relying on a ceiling, because an item with no weight contributes nothing to the total and silently defeats the rule.
- RiskThe floor blocks a genuine small order that could ship by parcel
- MitigationSet the floor against the lane it is protecting rather than the catalogue as a whole, so small parcel-friendly orders are not swept up by a pallet threshold.
- RiskOversized buyers abandon rather than enquire
- MitigationTurn on the Contact us button and say plainly that larger orders are handled by freight quote, so the refusal reads as a different process rather than a rejection.
What to take away
- 1
Weight is the honest dimension when freight is the constraint, because quantity does not know what an item weighs.
- 2
Read weights from the product data you already maintain, or you will be maintaining the same numbers twice and trusting the copy.
- 3
The heaviest carts are the most valuable ones, so a ceiling without a contact route throws away the best orders you receive.
Questions
Questions merchants ask
- How do I set a cart weight limit on Shopify?
- Create a weight rule with a minimum, a maximum or both. It reads the weights already recorded on your products, adds up the cart, and a Shopify Function compares the total against your band at checkout. Nothing extra has to be maintained as long as product weights are accurate.
- Where does the weight come from?
- From your existing Shopify product and variant weights, so there is no second source of truth to keep in step. If a variant has no weight recorded it contributes nothing to the total, which is worth auditing before you rely on a ceiling to protect a carrier booking.
- Which units are supported?
- Pounds, ounces, kilograms and grams. The rule is written in the unit you already use for your catalogue, and the storefront message states the limit in that same unit so a buyer never has to convert anything to understand why a cart was refused.
- Why set a minimum weight rather than only a maximum?
- Because some shipping methods only make financial sense above a threshold. A pallet booking that costs the same whether it carries 4 lb or 400 lb is a loss at the low end, so a floor keeps those orders out of a lane that was never priced for them.
- What happens to an order that is too heavy?
- It is stopped at checkout with a message you write, and a Contact us button can turn it into a freight enquiry. That moves the conversation from the warehouse, where a failed label means a phone call and a rebooking, to the product page, where it is still a sale.
More case studies
Five other stores, five other rules
Every quick-start template in the app has a story behind it. Here are the rest.
Minimum order quantity
A beverage wholesaler stops buyers breaking a case of 6.
Maximum order quantity
A parts retailer stops one order clearing the shelf.
Sell in pack multiples
A candle maker makes the box and the order the same thing.
Minimum order value
A B2B food supplier refuses carts that lose money.
Limit quantity per customer
A collectibles brand stops resellers coming back for more.