What Is PKU (Price per Kilogram) and Why It Matters

When shopping for 3D printing filaments, you might see two spools: one priced at $20 and another at $24. At first glance, the $20 spool seems like the better deal. But what if the $20 spool contains only 0.75 kg of filament while the $24 spool has 1.0 kg? Suddenly, the "cheaper" option actually costs more per kilogram. This is where PKU (Price per Kilogram) becomes essential—it's the metric that shows you the true cost of filament, regardless of spool size or brand.

1. The Problem with Comparing Price per Spool

Imagine you're comparing two PLA filament spools:

• Spool A: $20 for 0.75 kg
• Spool B: $24 for 1.00 kg

At first glance, Spool A seems cheaper because $20 is less than $24. However, this comparison ignores a critical factor: the actual amount of filament you're getting. When you look at the price per kilogram, Spool A costs $26.67/kg while Spool B costs $24.00/kg—making Spool B the better value despite its higher sticker price.

Why "cheap" can be misleading: Manufacturers use different spool sizes (0.5 kg, 0.75 kg, 1.0 kg, 1.5 kg, etc.), and some brands may price smaller spools attractively to make them appear more affordable. Without PKU, you can't make fair comparisons between different brands or spool sizes.

2. What PKU Means

PKU stands for Price per Kilogram—a simple but powerful metric that answers the question: "How much am I really paying for 1 kg of usable filament?"

PKU normalizes filament prices by weight, allowing you to compare filaments of different spool sizes, brands, and weights on an equal footing. It's the same concept used in grocery stores when comparing prices per pound or per kilogram—you're comparing the cost of the actual product, not the packaging.

Important note: Always use the net weight (the actual filament weight, excluding the spool) when calculating PKU. Some manufacturers list gross weight, which includes the spool and can be misleading.

3. How to Calculate PKU

The formula for PKU is straightforward:

Example calculations:

Even though Spool A has a lower sticker price, Spool B offers better value per kilogram. This is why PKU is essential for making informed purchasing decisions.

4. Why PKU Is Better Than Just "Cheap or Expensive"

PKU provides several key benefits:

• Fair comparison: Compare filaments from different brands and spool sizes using a single, standardized metric
• Budget planning: Calculate exactly how much filament you'll get for your budget
• Value assessment: Identify which filaments offer the best value, not just the lowest price
• Transparency: See through marketing tactics that use smaller spools to appear cheaper

However, PKU isn't everything: While PKU tells you the cost per kilogram, it doesn't measure print quality, color consistency, mechanical properties, or reliability. A filament with a low PKU but poor quality might end up costing more in failed prints and wasted material. Always use PKU alongside other metrics like user ratings, reviews, and technical specifications.

5. How FilamentRank Uses PKU

FilamentRank uses PKU as a core metric to help you find the best value filaments. Our comparison tool:

• Calculates PKU for every filament in our database
• Allows you to sort and filter filaments by PKU to find the best prices
• Combines PKU with quality metrics (ratings, reviews, OVI) to show overall value
• Helps you answer: "Which filament gives me more usable material per dollar?" instead of just "Which spool is cheaper?"

By using PKU, FilamentRank shifts the focus from sticker price to true value, helping you make smarter purchasing decisions that balance cost and performance.

6. Limitations of PKU (and How to Use It Wisely)

PKU is a powerful tool, but it has limitations. It doesn't measure:

• Print quality or surface finish
• Color consistency or accuracy
• Mechanical properties (strength, flexibility, temperature resistance)
• Diameter tolerance and consistency
• Spool winding quality
• Brand reliability and customer support

Use PKU alongside:

• User ratings: See what other users think about print quality and reliability
• Review counts: More reviews often indicate more reliable data
• Technical specifications: Check diameter tolerance, recommended temperatures, and material properties
• OVI (Overall Value Index): FilamentRank's metric that combines PKU with quality factors

The best approach is to use PKU to narrow down your options by price, then evaluate the top candidates based on quality metrics and reviews.

7. Short Summary

• PKU (Price per Kilogram) is the true cost of filament, calculated by dividing spool price by net weight in kilograms
• PKU enables fair comparisons between different brands and spool sizes, revealing which filaments offer the best value
• Always use net weight (filament weight excluding spool) when calculating PKU, not gross weight
• PKU is essential but not sufficient—combine it with quality metrics like ratings, reviews, and technical specifications for the best decisions
• FilamentRank uses PKU to help you find filaments that balance cost and performance, shifting focus from "cheap" to "best value"