Filament Calculator: Grams, Meters and Cost Per Print
Last reviewed . The calculator runs in your browser and stores nothing.
What this calculator does
The tool above takes a print's filament weight in grams, or its volume in cubic centimeters, and returns three numbers: the weight, the length of filament that weight represents, and what that much filament cost you. Length matters when you want to know whether a partly used spool will finish a job. Weight and cost matter when you are pricing a part, comparing spools, or deciding whether a big print is worth it. Everything runs in your browser from the values you type, and nothing is looked up or stored.
The formula, step by step
Filament is a long, thin cylinder of plastic, so converting weight to length is plain geometry plus one material property.
- Cross-section area. Area = pi × (d / 2)², where d is the filament diameter. Work in centimeters so the units line up with density: 1.75mm is 0.175 cm, so the radius is 0.0875 cm and the area is about 0.02405 cm².
- Grams per centimeter. Multiply that area by the density. At 1.24 g/cm³, one centimeter of 1.75mm filament weighs about 0.0298 g, which is about 2.98 g per meter.
- Meters. Meters = grams / (density × area), with the result converted from centimeters to meters.
- Volume input. If you enter cubic centimeters instead of grams, the tool first multiplies volume by density to get grams, then follows the same steps.
- Cost. Cost = (grams / 1,000) × your price per kilogram.
Worked example for 1.75mm PLA
These are round illustrative numbers, not data about any product. Say your slicer reports 100 g for a print, you use 1.75mm PLA, you leave density at 1.24 g/cm³, and your spool cost $20 per kilogram.
- Area: pi × 0.0875² ≈ 0.02405 cm²
- Density × area: 1.24 × 0.02405 ≈ 0.0298 g per centimeter
- Length: 100 / 0.0298 ≈ 3,353 cm, or about 33.5 meters
- Cost: 0.1 kg × $20 = $2.00
The same arithmetic gives these reference points at 1.24 g/cm³:
| Filament | Grams per meter | Meters per 100 g | Meters per 1 kg |
|---|---|---|---|
| 1.75mm | about 2.98 | about 33.5 | about 335 |
| 2.85mm | about 7.91 | about 12.6 | about 126 |
A 2.85mm strand has roughly 2.65 times the cross-section of a 1.75mm strand, so the same weight is far shorter. Pick the diameter your printer actually takes, because entering the wrong one changes the length by that same factor. The cost does not change, since cost depends only on weight.
Why density is an editable field
The default is 1.24 g/cm³, the figure Prusa gives in the Prusament PLA safety data sheet (opens in a new tab) (revision dated August 19, 2024). Manufacturers do not all publish the same value. Polymaker's technical data sheet for PolyLite PLA lists 1.17 g/cm³ at 23°C (opens in a new tab), measured to ISO 1183, while its PolyLite PLA Pro sheet lists 1.22 g/cm³ (opens in a new tab). Pigments, fillers, and modifiers in PLA+, silk, matte, or wood blends all shift the number.
If your brand publishes a density, type it into the field. The effect is modest but real: at 1.17 g/cm³, a kilogram of 1.75mm filament comes out to about 355 meters instead of about 335. For a single print the gap is a meter or two. For deciding whether the last 80 g on a spool will finish a long job, it can be the difference between a clean finish and a runout halfway up the part.
Where the input numbers come from
The most accurate input is the filament weight your slicer reports after slicing, because it already accounts for walls, infill, supports, and the skirt or brim. Most slicers show a weight, a length, or both in the print summary. If your slicer gives length but not weight, you can still use this page as a cross-check on the density setting it uses.
The volume option suits a different situation: you have a model's volume from CAD software or a mesh tool and no slicer output yet. Be careful here. A solid model's volume describes the part as if it were printed completely full. Real prints are mostly hollow inside, so a 50 cm³ model entered at 1.24 g/cm³ gives 62 g, which is the ceiling for a part printed at full density, not the amount a typical sliced print will use. Our guide on how much filament a print needs covers estimating real usage from infill and wall settings, so this page does not repeat it.
Getting a fair price per kilogram
The cost line is only as good as the price you enter. Use what you actually paid divided by the net filament weight, not the gross weight with the spool. If you bought a multipack, divide the total price by the combined net weight of every spool in it. That is the same method pla.deals uses: offer price divided by total net filament weight across all spools in a listing, which you can see on the price per kg page. Prices on the site carry the time they were last verified against Amazon, so treat any figure you copy from a listing as a snapshot.
If you print a lot, the price you pay per kilogram usually moves your cost per part more than any other input. Comparing bulk spools or the lowest current price per kg against what you paid last time is a quick way to see what a cheaper source would save across a year of prints.
What the estimate leaves out
This calculator converts and multiplies. It does not know about:
- Purge and waste. Multi-color prints flush filament between colors, and that waste may or may not appear in your slicer's total depending on the software and settings.
- Failed prints. A print that detaches at 80 percent still used 80 percent of its filament.
- Diameter variation. A spool that runs slightly thick or thin changes grams per meter in proportion to the square of the diameter.
- Electricity and wear. For power cost and a failure allowance, use the print cost calculator, which builds on the filament figure from this page.
Frequently asked questions
How many meters are on a 1 kg spool of 1.75mm PLA?
At 1.24 g/cm³ it works out to about 335 meters of filament. At a lower published density such as 1.17 g/cm³ it is about 355 meters. Check your brand's data sheet and enter its density for a closer figure.
Can I use this for PETG or other materials?
Yes, as long as you change the density to the value your filament maker publishes. The geometry is the same for any round filament. Leaving the PLA default in place for a denser or lighter material will make the length and weight conversion wrong.
Why does my slicer show a slightly different length?
Slicers use whatever density and diameter are set in the filament profile, and those may not match the values here. Set both tools to the same diameter and density and the results should agree closely.
Does the cost include the empty spool?
No. Enter the price per kilogram of filament only, based on net weight. The empty spool's weight is not printable material and should not be part of the calculation.
Also see the print cost calculator.