Filament Length and Volume Calculator

1. Enter the filament weight in grams.
2. Choose your material so the right density is used.
3. Choose your diameter, 1.75 mm or 2.85 mm.
4. Read the length, volume and grams per metre.

Filament length is how many metres a given weight of filament makes, and volume is how much space that plastic occupies. Both come from the weight, the material density and the strand diameter, since filament is a long cylinder of known cross-section.

Makers need these figures to check how much is left on a spool, to work out whether a print will finish before the filament runs out, and to convert between the grams a slicer reports and the length a spool is sold by. It is the answer to the most common workshop question of all, whether the roughly 40 metres left on a nearly-empty spool is enough to finish the job in front of you or whether it is time to load a fresh one.

1. Divide the weight by the density for the volume in cubic centimetres.
2. Find the cross-section area from the diameter: pi times the radius squared.
3. Divide the volume by the area, with unit conversion, for the length.
4. Divide the weight by the length for grams per metre.

Because density and diameter are fixed for a given filament, weight and length are simply two ways of measuring the same spool. Once you know the grams per metre for your filament, you can flip between the two in your head without touching a calculator at all.

Take 1 kilogram of 1.75 mm PLA. PLA has a density of about 1.24 grams per cubic centimetre, so 1000 grams is roughly 806 cubic centimetres. The 1.75 mm strand has a cross-section of about 2.4 square millimetres. Dividing the volume by that area gives around 335 metres. A 2.85 mm PLA spool of the same weight is much shorter, near 126 metres, because the thicker strand uses the plastic faster.

Weight

Length scales directly with weight, so a half spool is half the length of a full one.

Material Density

Denser filaments pack more grams into the same length, so they run shorter per kilogram.

Diameter

A 2.85 mm strand has far more cross-section than 1.75 mm, so it is much shorter for the same weight.

Fillers and Additives

Wood, metal and carbon fills change the density, shifting the length from the plain-plastic figure.

Approximate length of a 1 kg, 1.75 mm spool by material.

Lighter materials such as ABS give more metres per kilogram, while denser ones such as PETG give fewer.

Checking a Spool

Weigh what is left and convert to the length remaining.

Will It Finish?

Compare the length or weight a print needs against what is on the spool.

Buying Filament

Compare spools sold by length against those sold by weight on equal terms.

1. Wrong Density

Using PLA density for PETG or a filled filament throws the length out; pick the right material.

2. Ignoring Diameter

A 2.85 mm spool is far shorter than 1.75 mm for the same weight; set the correct diameter.

3. Forgetting the Empty Spool

When weighing a part-used spool, subtract the empty spool weight first.

4. Mixing Units

Keep weight in grams and diameter in millimetres so the conversion lines up.

The conversion is exact for the density and diameter you choose. Real filament varies slightly in diameter and density, so treat the result as very close, not perfect.

About 335 metres for 1.75 mm PLA, and roughly 126 metres for 2.85 mm PLA, because the thicker strand uses plastic faster.

Divide the weight by the density for volume, then divide by the strand cross-section area. Weight, density and diameter are all you need.

Divide the print grams by the grams per metre for your filament. At about 3 grams per metre for 1.75 mm PLA, an 80 gram print is roughly 27 metres.

Yes, a lot. A 2.85 mm spool is well under half the length of a 1.75 mm spool of the same weight.

PLA is about 1.24, PETG 1.27, ABS 1.04 and nylon 1.14 grams per cubic centimetre. Filled filaments differ, so check the spool.

Weigh the spool, subtract the empty spool weight, and convert the remaining grams to length with this tool.

The weight of one metre of filament. For 1.75 mm PLA it is about 3 grams per metre; multiply by a length to get weight.

Volume links weight and length, and it is what your slicer uses internally. It also helps compare materials of different density.

No. The calculator runs entirely in your browser and nothing you enter is stored or sent anywhere.

• 3D printing filament (Wikipedia).
• Density (Wikipedia).
• Polylactic acid (PLA) (Wikipedia).