Filacoste

Filament grams to metres converter

Type the grams and it gives you the metres, or the other way round. By material and diameter.

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The filament
g/cm³
mm
g
Convert
g
m

Type in either field: the other one updates on its own.

How it works

  • 1. The filamentMaterial and diameter: 1.75 mm or 2.85 mm.
  • 2. What you knowType grams or metres, it doesn't matter which end you start from.
  • 3. The conversionMetres, volume and how much of the spool that is.

How grams of filament turn into metres

Filament is a cylinder, so the conversion is pure geometry and needs no lookup table:

  1. Volume = grams ÷ material density (in g/cm³). 50 g of PLA (1.24 g/cm³) is 40.3 cm³ of plastic.
  2. Cross-section = π × (diameter ÷ 2)². A 1.75 mm filament has 0.0241 cm² of section; a 2.85 mm one has 0.0638 cm².
  3. Length = volume ÷ section. Those 40.3 cm³ give 1,676 cm, that is 16.8 metres.

That is why the same weight gives such different lengths: in 2.85 mm the strand is 2.65 times fatter, so the same grams give you 2.65 times fewer metres.

Why density changes the answer

ABS weighs 1.04 g/cm³ and PETG 1.27 g/cm³. With a one kilo spool of each, the ABS gives you about 400 metres and the PETG about 327: nearly 20% apart on material alone. If you buy by the kilo but plan by the metre — or the other way round — that gap lands straight in your pricing. All the densities are together in the filament density and price table.

What this is actually for

  • Knowing whether you'll make it. If there are 40 metres left on the spool and the part wants 120 g of PLA, you won't: 120 g is about 40 metres exactly, and the tail of a spool is always lost.
  • Buying well. Two spools at the same price per kilo are not the same price per metre if they are different materials.
  • Estimating leftovers. Weigh a part-used spool on a kitchen scale, subtract the weight of the empty core (200-250 g on plastic ones) and convert to metres.

How far off this can be

It is exact if the filament is exact. In practice, the diameter tolerance brands quote (±0.02 mm on good ones, ±0.05 mm on cheap ones) makes the real length drift by 1% to 3%. Fillers matter too: a PLA with wood or carbon fibre in it doesn't have the density of pure PLA, and there it pays to type the density in by hand.

Once you have the grams straight, the 3D printing cost calculator tells you what that part really costs, and how long a 1 kg spool lasts has the metres for every material already worked out.

Frequently asked questions

How many metres is 1 kg of 1.75 mm PLA filament?

About 335 metres, at a density of 1.24 g/cm³.

In 2.85 mm, the same kilo comes to about 126 metres.

How many grams is 10 metres of filament?

In 1.75 mm PLA, about 30 grams. In PETG, about 31 grams, and in ABS about 25.

In 2.85 mm the same 10 metres is about 79 grams of PLA, because the strand is much thicker.

How do I know how much filament is left on a part-used spool?

Weigh the whole spool on a kitchen scale and subtract the weight of the empty core, usually between 200 and 250 grams on plastic spools and often printed on the spool itself.

What's left is the grams of filament; type them in above and you have the metres.

Does colour change the weight of filament?

Very little, but it does. Pigments and fillers shift the density slightly: a PLA with metallic sparkle or wood fibre doesn't weigh the same as plain PLA.

If you need precision, type the density the manufacturer quotes into the density field.

Why does my spool hold fewer metres than this sum says?

Almost always because of diameter tolerance: filament that runs slightly thick gives fewer metres for the same grams.

Also because plenty of «1 kg» spools actually hold between 990 and 1,000 grams of material.

More tools and guides

Filament length — Of the spool: —