The Filament Length Calculator helps 3D printing hobbyists, engineers, and production managers figure out how much printable filament they have on a spool. It converts the filament weight into an accurate length based on the material type and its diameter. Knowing this length is very important for planning prints, avoiding material run-outs, and reducing waste. This calculator belongs to the 3D Printing Material Calculator category and is widely used in both hobby and industrial 3D printing.
formula of Filament Length Calculator
Filament Length = (Weight) / (Cross-sectional Area × Density)
For round filament, the full practical version is:
Filament Length = (Weight) / [π × (Diameter / 2)² × Density]
Where:
Weight is the filament weight in grams or kilograms
Diameter is the filament diameter in millimeters (common sizes: 1.75 mm or 2.85 mm)
Density is the material density in g/mm³ (for example, PLA is about 1.24 g/cm³ which is 0.00124 g/mm³)
π is about 3.14159
Step-by-step:
- Find the cross-sectional area (A):
A = π × (Diameter / 2)² - Calculate filament length (L):
L = Weight / (A × Density)
Common Filament Length Reference Table
This table shows rough length estimates for standard filament sizes and weights. It helps users plan prints without manual calculations every time.
| Filament Type | Diameter (mm) | Spool Weight (g) | Approx. Length (m) |
|---|---|---|---|
| PLA | 1.75 | 500 | ~165 |
| PLA | 1.75 | 1,000 | ~330 |
| PLA | 2.85 | 1,000 | ~120 |
| ABS | 1.75 | 1,000 | ~340 |
| PETG | 1.75 | 1,000 | ~325 |
These are average values and can change slightly based on brand and exact density.
Example of Filament Length Calculator
Let’s check a step-by-step example.
You have:
Weight = 1,000 g
Diameter = 1.75 mm
Density (PLA) = 0.00124 g/mm³
- Find cross-sectional area:
A = 3.14159 × (0.875)²
A = 3.14159 × 0.7656 ≈ 2.405 mm² - Filament Length:
L = 1,000 / (2.405 × 0.00124)
L = 1,000 / 0.002984 ≈ 335,175 mm
Convert to meters:
L ≈ 335.2 meters
So, you have about 335 meters of filament on a 1 kg spool.
Most Common FAQs
Knowing filament length helps you plan prints properly. It avoids running out of material during a big print and helps check if a leftover spool has enough for your next project.
Yes. Different plastics have different densities. For example, PLA is denser than ABS. This means the same weight spool of PLA will be slightly shorter than a spool of ABS.
Labels are a good guide but can vary. Measuring filament diameter accurately and using this calculator gives you a more precise length so you can avoid surprises during printing.