Why Are Jars So Expensive to Ship?

How Box Size and Density Affect Shipping Costs

One of the most common questions we hear—especially from slime businesses placing smaller orders—is:
“Why does shipping cost so much for jars?”

It’s a fair question. Jars may look lightweight, but when it comes to shipping, what you see and what carriers charge are often two very different things. Two big factors drive shipping costs: box size (dimensional weight) and density.

Let’s break it down in a simple, no‑jargon way.

1. Shipping Is Based on More Than Just Weight

Most carriers (UPS, FedEx, USPS) no longer price shipments solely on how much they weigh. Instead, they charge based on whichever is greater:

• Actual weight (what the box weighs on a scale), or
• Dimensional weight (how much space the box takes up on the truck)

Dimensional weight rewards small, dense packages—and penalizes large boxes that don’t weigh much.

2. Jars = Air + Plastic = Larger Boxes

Even though plastic jars are lightweight, they:

• Take up a lot of physical space
• Can’t be compressed
• Require protective packaging to prevent cracking or deformation

All of that means:

• Larger boxes
• More empty space (“air”) inside each shipment
• A higher dimensional weight than you might expect

So even if the jars themselves aren’t heavy, the box they require may push the shipment into a higher shipping tier.

3. Density Matters (A Lot)

Carriers love dense shipments—think bolts, books, or metal parts.
Jars are the opposite.

Low-density items:

• Fill space quickly
• Hit dimensional weight limits fast
• Cost more per unit to move

This is why:

• A small box of heavy parts can ship cheaply
• A larger box of lightweight jars can cost significantly more

It’s not about value—it’s about physics and truck space.

4. Small Orders Feel the Impact the Most

On larger pallet or bulk shipments, shipping costs are spread across many units.
On smaller orders, the box-to-product ratio is much higher, so freight feels expensive by comparison—even when rates are fair.

This is often why customers notice shipping costs more on:

• Trial runs
• Small replenishment orders
• Mixed or partial case quantities

5. How You Can Offset Shipping Costs

One option some slime businesses choose is to ship using their own UPS or FedEx account, especially if they:

• Have negotiated rates
• Ship frequently
• Want more control over freight charges

If you provide us with shipping labels, we’re happy to:

• Apply them to your boxes
• Ship your order using your carrier account

And if you don’t yet have a shipping account, setting one up is usually quick and free.

The Bottom Line

Jars aren’t expensive to ship because they’re heavy—they’re expensive because:

• They require space
• Space costs money
• Carriers price by volume, not just weight

Understanding how dimensional weight and density work can help you:

• Plan orders more efficiently
• Decide when to bundle quantities
• Determine whether using your own carrier account makes sense

If you ever want help comparing shipping options for your order, just ask—we’re always happy to walk through it with you.