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Category Engineering Converters

Material / Density

Custom Density (g/cm³)

Filament Diameter

1.75 mm 2.85 mm Custom

Spool Brand (Tare Weight)

Custom Tare Weight (g)

Current Gross Weight (g) Weigh the spool on a kitchen scale.

Original Spool Cost (Optional)

Required Length from Slicer (m) (Optional)

Remaining Length

0 m

Net Filament Weight

0 g

Estimated Value

$0.00

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About

Running out of filament during a 20-hour print is a 3D printing operator's worst nightmare. It results in wasted material, lost time, and the frustration of a failed part. Estimating remaining material by eye is notoriously inaccurate due to varying spool hub diameters and winding tightness. This tool solves that problem by using the physical properties of the plastic to convert mass into length.

Accuracy depends heavily on two variables: the material density and the empty spool weight (tare). Different manufacturers use significantly different plastic blends and spool designs. A generic density value for PLA might be off by 5%, which translates to several meters of error on a near-empty roll. This calculator provides a database of specific manufacturer densities and spool weights to minimize that margin of error. It determines exactly how much material is available to the extruder.

Formulas

The conversion relies on the relationship between mass, volume, and geometric area. First, we determine the volume of the filament material by isolating the net weight from the gross weight.

{

m_net = m_gross − m_tareV = m_netρ

Once the volume V is known, we calculate the cross-sectional area A of the filament strand, assuming a perfect circle. Finally, dividing the volume by the area yields the length L.

L = Vπ ⋅ d2²

Where d is the filament diameter (usually 1.75mm or 2.85mm).

Reference Data

Material / Brand	Density (g/cm³)	Est. Tare Weight (g)	Notes
PLA (Polylactic Acid)	1.24	N/A	Standard generic density
PETG	1.27	N/A	Higher density than PLA
ABS	1.04	N/A	Lightweight
TPU (95A)	1.21	N/A	Flexible
Prusament	Var.	190	Plastic honeycomb sides
Sunlu / Jayo	Var.	230	Standard black plastic
eSun	Var.	220	Clear/Black plastic
Hatchbox	Var.	225	Standard spool
Overture (Cardboard)	Var.	140	Pressed cardboard
Bambu Lab	Var.	250	Reusable spool (High temp)
Polymaker (Cardboard)	Var.	150	Cardboard sides

Frequently Asked Questions

Tare weights vary by production batch. A standard black plastic spool typically weighs between 220g and 240g. Cardboard spools are significantly lighter, often 140g to 160g. For critical prints where you are cutting it close, weigh an empty spool from the same manufacturer if you have one.

Yes, but usually negligibly for length estimation. Moisture increases the weight of the filament without adding usable plastic volume. If your filament is heavily saturated (e.g., wet Nylon), the calculated length will be slightly overestimated because part of the mass is water.

Different plastics have different specific gravities. A 1kg spool of PLA (Density 1.24 g/cm³) has less total length than a 1kg spool of ABS (Density 1.04 g/cm³) because ABS is lighter. Using the wrong density can lead to a calculation error of over 15%.

Select "Custom / Generic" in the spool dropdown. Weighing an empty spool of similar construction is the best proxy. If uncertain, assume a heavier tare weight (e.g., 250g) to build a safety margin into your result.

Always aim for at least a 10-15% buffer. The slicer software's estimated usage is theoretical and does not account for purge lines, skirt/brim, or flow rate adjustments during the print.