How Much Filament Do I Need for a Print?

The short answer

Your slicer already knows. After you slice a model, PrusaSlicer, Bambu Studio, OrcaSlicer and Cura all report the filament it will use, in grams and in meters. Add a margin of your own on top for the purge line and the occasional restart (the tables below use 10% as an example), and compare that to what is left on your spool. A full 1kg spool of 1.75mm PLA holds roughly 335 to 355 meters, and a print's material cost is simply its weight in grams times the price per kg, divided by 1,000.

Where the slicer's number comes from

A slicer turns the model into toolpaths, adds up the length of filament each path will push through the nozzle, then converts that length to weight using the density in your filament profile. Everything that changes the toolpaths changes the result:

• Walls and top or bottom layers. More perimeters and thicker skins add material quickly on large parts.
• Infill percentage and pattern. Going from a light to a heavy infill can multiply the weight of a chunky part.
• Supports, brims and rafts. These are real filament even though you throw them away.
• Multicolor purging. Printers that change colors through a single nozzle flush plastic into a purge tower or waste chute at each swap. The more color changes a print has, the more purge it produces, and slicers usually list that weight separately from the model.
• Scale. Weight rises with volume, so doubling a model's size in every direction makes it roughly eight times heavier.

Because the gram figure depends on the density setting, a wrong density gives a wrong answer. Densities published by manufacturers vary: Polymaker lists 1.17 to 1.24 g/cm³ for PolyMax PLA (opens in a new tab), and SUNLU's knowledge base lists 1.21 g/cm³ for its PLA+ and 1.21 to 1.36 g/cm³ for its PLA (opens in a new tab). If your profile's density is lower than the formula's real density, the slicer will underestimate the weight, and the reverse is also true.

Diagnostic steps: getting an accurate estimate

1. Pick the right filament profile. Use the brand's own profile if your slicer has one, or set the density from the manufacturer's data sheet.
2. Check the diameter setting. It should read 1.75mm for 1.75mm filament. A profile set to 2.85mm will give nonsense numbers.
3. Slice with everything enabled. Turn on the supports, brim and purge tower you will actually use before reading the total.
4. Read the per-object breakdown. Many slicers split model, support and purge weight. If supports dominate, reorienting the part can save more than any infill tweak.
5. Weigh the spool before a long print. Put it on a kitchen scale and subtract the empty spool weight. Elegoo, for instance, lists its empty cardboard spool at 154 ± 10 g (opens in a new tab); other brands differ, so weigh an empty one of the same brand once and note it.
6. Compare and decide. If the remaining weight is within your margin of the slicer total, swap to a fresh spool or plan a mid-print filament change rather than risk running out.

Reference table: meters per kilogram from density

Length per kilogram follows from geometry. A 1.75mm filament has a cross-section of about 2.405 mm², so one meter has a volume of 2.405 cm³. Multiply by density to get grams per meter, then divide 1,000 by that to get meters per kilogram. The densities below are the published values cited above.

The math lines up with what manufacturers print on the box. eSUN states a total length of 340 to 350 meters (opens in a new tab) for its 1kg PLA+ spool, which sits inside the computed range. Diameter tolerance shifts the figure slightly: eSUN's ±0.03mm tolerance (opens in a new tab) means a strand anywhere from 1.72 to 1.78mm, which moves length per kilogram by roughly 3.5% either way. For 2.85mm filament, each meter weighs about 2.65 times as much, so a kilogram covers far less length.

How much does 1kg of PLA print?

Divide 1,000 by the part's weight in grams, then knock off a little for waste. Using hypothetical part weights to show the math:

Large prints are where planning matters. Two 400 g parts leave about 200 g on the spool, not enough for a third, and a spool that ends partway through a long print wastes the whole job unless your printer supports runout detection and resume.

Cost to print a 3D model

The material cost formula is: grams used × price per kg ÷ 1,000. At a hypothetical $20 per kg, every gram costs 2 cents, so an 85 g print costs $1.70 in filament. At $15 per kg the same print costs about $1.28. Electricity, nozzle wear and failed prints come on top of that and are not part of this formula.

Price per kg is the figure to compare, not the sticker price, because spool sizes vary. Our PLA filament price per kg page ranks current listings that way. pla.deals divides the offer price by the total net filament weight across every spool in the listing, and spools of 250 g or less are labelled samples and kept out of cheapest rankings. If you print a lot, bulk PLA and 10kg bundles are where the per gram cost tends to fall.

Suitable products

For occasional printing, a standard 1kg spool covers dozens of small parts. If your slicer totals regularly run into hundreds of grams, larger spools and multi-spool bundles cut the number of spool swaps and usually lower the price per kg; the live grid below shows current options, and cheapest PLA filament sorts them by that figure. The filament finder lets you filter by spool weight.

Common mistakes

1. Reading the model weight and ignoring supports and purge. On multicolor jobs the waste adds up with every color change.
2. Leaving the slicer on a generic density when your brand publishes something different.
3. Weighing the spool without subtracting the empty reel. Spool weights differ by brand and material.
4. Planning to the last gram. Leave a margin; a print that runs out at 98% is a total loss.
5. Comparing spools by sticker price instead of price per kg.
6. Forgetting that scale is cubic. A model at 150% size uses more than three times the filament.

Frequently asked questions

How many meters are on a 1kg spool of PLA?

For 1.75mm PLA, roughly 335 to 355 meters at the densities Polymaker publishes for PolyMax PLA. A denser formula, like SUNLU's PLA at its upper figure of 1.36 g/cm³, gives closer to 306 meters.

Is the slicer's estimate accurate?

It is close if the density and diameter in your profile match the filament. Actual use can differ slightly with flow calibration, so keep a margin.

How do I tell how much filament is left on a spool?

Weigh it and subtract the empty spool weight. Divide the remainder by your filament's grams per meter, about 2.98 g at 1.24 g/cm³, to convert to length.

Does a bigger nozzle use more filament?

The model's solid volume does not change, but a larger nozzle lays wider lines. With the same number of perimeters, walls get thicker and the gram total rises, so check the slicer figure after switching.