How many metres are in a 1 kg spool?

About 335 m for 1.75 mm PLA, or roughly 126 m for 2.85 mm, since the thicker filament uses more material per metre.

How do I work out the cost of a print?

Divide the grams your slicer reports by 1,000 and multiply by the spool price. A 25 g print from a £20 spool costs about 50p in material.

How much filament is left on my spool?

Weigh it and subtract the empty spool weight, typically 150 to 250 g. Forgetting to subtract it overestimates what remains considerably.

Does material choice change the length?

Yes, through density. A kilogram of ABS at 1.04 g/cm³ gives noticeably more length than a kilogram of PETG at 1.27.

Filament Calculator - Length, Weight and Cost

3D Printing Filament Calculator

Slicers report filament use in metres, spools are sold by weight, and cost depends on both. This calculator converts between them for any material.

Formula

Volume (cm³) = π × (diameter ÷ 2)² × length ÷ 1,000 · Mass = volume × density

Diameter and length in millimetres
PLA density 1.24 g/cm³, ABS 1.04, PETG 1.27

10 m of 1.75 mm PLA: 24.05 cm³ × 1.24 = 29.8 g

Length, Volume and Weight

Filament is a cylinder, so its volume is cross-sectional area times length:

Volume = π × (diameter ÷ 2)² × length, then weight = volume × density

A 1 kg spool of 1.75 mm PLA (density 1.24 g/cm³) holds about 335 metres. The same weight in 2.85 mm holds only 126 metres, because the thicker strand packs more material per metre.

Densities by Material

PLA: 1.24 g/cm³
ABS: 1.04 g/cm³
PETG: 1.27 g/cm³
TPU: around 1.21 g/cm³
Nylon: around 1.14 g/cm³

Density matters for cost per print: a kilogram of ABS stretches further than a kilogram of PETG, because it is less dense.

Working Out Print Cost

Cost = (grams used ÷ 1,000) × spool price

A 25 g print from a £20 spool costs 50p in material. That is usually the smallest part of the true cost — electricity, failed prints, and the machine's own depreciation typically outweigh it.

Note that spool weight is net filament: an empty spool adds 150–250 g, so weighing a part-used spool without subtracting it will badly overestimate what remains.

Quick Reference

Filament by the metre, and how far a 1 kg spool goes.
Diameter	Material	Grams per metre	1 kg spool
1.75 mm	PLA (1.24)	2.98 g	335 m
1.75 mm	ABS (1.04)	2.50 g	400 m
1.75 mm	PETG (1.27)	3.05 g	327 m
2.85 mm	PLA (1.24)	7.91 g	126 m

Frequently Asked Questions

How many metres are in a 1 kg spool?: About 335 m for 1.75 mm PLA, or roughly 126 m for 2.85 mm, since the thicker filament uses more material per metre.
How do I work out the cost of a print?: Divide the grams your slicer reports by 1,000 and multiply by the spool price. A 25 g print from a £20 spool costs about 50p in material.
How much filament is left on my spool?: Weigh it and subtract the empty spool weight, typically 150 to 250 g. Forgetting to subtract it overestimates what remains considerably.
Does material choice change the length?: Yes, through density. A kilogram of ABS at 1.04 g/cm³ gives noticeably more length than a kilogram of PETG at 1.27.