It’s a classic 3D printing dilemma: You’re halfway through a project, realise you’re low on your favourite PLA or ABS, and head online to grab a single spool. But when you hit the checkout, the shipping rate makes you double-take.
Here is a little industry secret: Shipping one spool of filament is almost always a bad deal for your wallet. Because we use live shipping rates, the cost is determined by freight tiers. If you want the most bang for your buck, the "Sweet Spot" is almost always two spools. Here’s why.
The "3kg Rule": Why 1 = 2
Freight companies don't charge by the kg below usually 5kg; they charge by weight brackets (tiers). For most couriers, the tier ends range from 500g, 1kg, 3kg, 5kg.
When you look at the math of a standard filament spool, the numbers tell a compelling story:
| Item | Net Filament | Gross Weight (Spool + Box) | Freight Tier |
| 1 Spool | 1kg | ~1.4kg | Under 3kg |
| 2 Spools | 2kg | ~2.8kg | Still Under 3kg |
Because two spools (including their packaging) typically sit right around 2.8kg, they fit perfectly into the exact same shipping bracket as a single spool.
The Result: You pay the same amount in shipping to move 2kg of plastic as you do to move 1kg.
Understanding "Dead Weight" vs. "Cubic Weight"
Shipping isn't just about how heavy a box is; it’s also about how much space it takes up in the truck. This is called Cubic (or Volumetric) Weight.
Filament spools are surprisingly "dense" packages. Even when we calculate the volume of the box, two spools rarely exceed that 3kg cubic threshold. This means that whether the courier looks at the scale or the measuring tape, the price stays the same for that second spool.
The "Cost Per Kilogram" Hack
For example, If you’re paying $15 for shipping:
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Buying 1 Spool: You’re adding $15 to the cost of that single kg.
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Buying 2 Spools: You’re adding only $7.50 to the cost of each kg.
By simply adding a second "emergency/backup/spare" roll of black or white PLA to your cart, you effectively halve your shipping overhead per item. This similar applies to smaller spares parts. We offer a helpful KG guide at cart for you effectively order within freight tier.
The Bottom Line
When you see a live shipping rate at checkout not just from us, remember that you’ve likely already paid for the "room" in that freight tier. You might as well fill it! Buying two spools or some extra spares doesn't just give you more material for your next marathon print; it ensures you aren't overpaying to ship products.