PETG Filament by Volume and Density

PETG filament: estimating grams and meters from part volume

PETG (polyethylene terephthalate glycol-modified) lands somewhere between PLA and ABS. It is tougher than PLA, less of a headache to print than ABS, and it shrugs off most chemicals. Its density usually runs around 1.27 g/cm³. Turn part volume into mass with mass = volume × density, then work that mass back into filament length with length = mass / (π · (d/2)² · density). Example: a 50 cm³ PETG part comes to 50 × 1.27 = 63.5 g, roughly 63.5 / 3.05 ≈ 21 m of 1.75 mm filament. A full 1 kg PETG spool of 1.75 mm filament gives you around 318 m, fewer meters per kilogram than ABS because PETG packs more mass into the same space.

PETG warps far less than ABS, which is why it prints fine on open-frame machines with no enclosure at all. Where it trips people up is stringing. PETG drinks up humidity, so drying the filament first (50 °C for 4–6 h) and bumping retraction a little makes a real difference. Some variants come with a manufacturer food-safe certification, but the FFF process still leaves microscopic gaps between layers that are awkward to clean, so for anything in direct contact with food you are better off with smooth-walled molds or a coat of epoxy afterward.

Applications

PETG is the everyday workhorse. It does prototyping well (functional parts that flex instead of snapping), it holds up as outdoor brackets (far more UV-stable than PLA), it handles chemical-handling parts (acids, oils and alcohols do not bother it), and it suits flexible-but-durable jobs like cable strain reliefs and hinge prototypes. Wiping the surface with isopropyl alcohol on a cloth leaves it semi-glossy. Just about any modern hobbyist printer, whether an Ender 3, a Prusa Mini or a Bambu A1, runs PETG straight out of the box.

FAQ

Why is my PETG stringy? It has soaked up moisture. Dry the spool at 50 °C for 4–6 hours in a filament dryer or oven, then add 1 mm to your retraction distance and push travel speed up to 150 mm/s.

Does PETG stick to PEI bed too well? Yes, and it catches a lot of people out. Put down a glue stick or some hairspray as a release layer, or move to glass at 75–85 °C. Skip the release agent and PETG will tear chunks right off a PEI sheet.

Is PETG truly food-safe? The raw pellets are food-grade, but FFF prints have those layer gaps that trap bacteria. PETG is fine for cookie cutters, scoop handles and other brief-contact items. Keep it away from cups and storage containers unless you seal them with food-safe epoxy.