Filament Usage Calculator
Check how much filament is left on your spool and whether you have enough to finish your next print. Supports 1.75mm and 2.85mm filament.
Filament Remaining
500g
50.0% of spool
168m
Approximate length
Spool Status
50.0%
Used
50.0%
Weight Used
500g
Length per gram
0.34m
Prints Left
10
PLA Properties
How Much Filament Is Left on My Spool?
Weigh the spool with a kitchen scale, subtract the empty spool weight (printed on the side, typically 200g to 250g for a 1kg spool), and you have the filament weight. Enter that figure and the calculator converts it to length using the filament's density and diameter. A 500g remainder of 1.75mm PLA (density 1.24 g/cm³) gives roughly 168 metres of usable filament - enough for about 10 small prints averaging 50g each.
If you do not want to dismount the spool, the calculator also accepts a percentage estimate. Looking at how full the spool is by eye is surprisingly accurate - 50% by visible volume is roughly 50% by weight because the filament is wound evenly. Just be aware that the cardboard or plastic core takes up 10 to 15% of the spool's outer volume, so what looks 25% full is closer to 15% by actual filament.
Density Differences That Matter
Different filaments have different densities, which changes the length you get from the same weight. PLA at 1.24 g/cm³ gives the standard length figure most calculators use. PETG at 1.27 is almost identical. ABS is lighter at 1.04 - meaning a 500g spool of ABS gives you about 19% more length than the same weight of PLA. Nylon at 1.14 sits in the middle. TPU varies between 1.20 and 1.25 depending on shore hardness.
Diameter is the bigger lever. 1.75mm filament is by far the most common - it works in nearly every consumer printer. 2.85mm (sometimes labelled 3mm) is used by Ultimaker, Lulzbot and a handful of older printers. The same weight of 2.85mm filament is much shorter in length because each metre is over twice the volume. A 1kg spool of 1.75mm PLA is roughly 335 metres; a 1kg spool of 2.85mm PLA is around 125 metres.
Will I Have Enough for the Next Print?
Enter your average print weight and the calculator works out how many full prints remain on the current spool. A common mistake is using the slicer's estimated filament weight without adding 5 to 10% buffer for support material, brim, and the purge line. A 50g print in your slicer is realistically 53 to 55g of actual material consumed.
If a print needs 80g and you have 75g left, do not start it - the print will fail at 95% complete and you will waste 5 hours. Either swap to a fresh spool or pick a smaller model. The [filament comparison](/filament-comparison) tool helps you choose between PLA, PETG and ABS when you are deciding what to load next, and the [3D print cost calculator](/3d-print-cost-calculator) puts the material cost into pounds and pence.
Frequently Asked Questions
How long does 1kg of PLA filament last?
A 1kg spool of 1.75mm PLA is approximately 335 metres of filament. At 50g per typical small print, that is 20 prints. For larger functional prints averaging 200g, it is 5 prints. Heavy use printing benchmarks and large models can burn through 1kg in a weekend; hobbyist printers making the occasional figurine might stretch a spool over 6 to 12 months.
How do I weigh just the filament without dismounting it?
Weigh the full spool with a kitchen scale (most printers' spools are too heavy for digital coffee scales). Look up the empty spool weight - it is usually printed on the spool itself or listed on the manufacturer's website. Subtract empty weight from total weight to get filament weight. For Bambu Lab, Prusament and most major brands, empty spools weigh 200 to 280g.
Why does PETG show different length than PLA at same weight?
PETG is slightly denser than PLA (1.27 vs 1.24 g/cm³), so a 1kg spool of PETG is about 2.5% shorter than a 1kg spool of PLA at the same diameter. The differences become noticeable across the range of materials: ABS at 1.04 g/cm³ gives 19% more length per kilogram than PLA, while Polycarbonate at 1.20 is nearly identical.
Should I keep the empty spool weight written down?
Yes. Either write it on the spool with a marker as soon as it arrives, or photograph the printed weight on the side. Once a spool is half-empty and tangled up with reload labels, the original printed empty weight gets hard to find. Tracking it lets you weigh accurately throughout the spool's life rather than guessing by eye in the final 30%.
Related Tools
3D Print Cost Calculator
Calculate the true cost of 3D printing including filament, electricity, printer depreciation, failure rate and labour. Supports FDM and resin printers with popular presets.
3D Printing Filament Comparison
Compare PLA, ABS, PETG, TPU, Nylon and ASA filaments side by side. See strength, flexibility, print difficulty, temperature and cost for each material.