How do I know how many grams a part weighs from the STL file?

The STL holds the closed geometry of the part, so its exact volume in cm³ can be computed. Weight is volume × material density × infill. PLA density is 1.24 g/cm³. On our calculator you just drop the file in.

Can I calculate cost straight from a Bambu Studio 3MF file?

Yes. 3MF is read normally, including multi-part plates and rescaled objects. If you already sliced it, the .gcode.3mf file is even better: it carries the weight and time already computed by the slicer, counting walls and supports.

Is the file I upload stored on the site?

No. Reading happens entirely inside your browser and nothing is sent to any server. The file never leaves your computer.

STL Calculator: Get the Part Cost Straight From the File

Quick answer: you don't have to guess how many grams a part will weigh. If you have the file, the volume is in its geometry — and our FDM calculator and resin printing cost calculator read that number straight from STL, 3MF, OBJ, PLY or G-code.

Why guessing weight is expensive

Most people selling printed parts estimate weight by eye or reuse the figure from a similar part. The error easily passes 30% either way. Underestimating eats your margin; overestimating loses the quote to someone who did the math.

How it works: volume comes from geometry

An STL file is a closed triangle mesh. You can compute its exact volume by summing the signed volume of each triangle relative to the origin — outside the solid the signs cancel out and the real volume remains. It isn't an estimate: it's the exact figure from the geometry.

With the volume, weight is a simple multiplication:

weight = volume (cm³) × material density (g/cm³) × infill

Common densities: PLA 1.24 · PETG 1.27 · ABS 1.04 · TPU 1.21 · ASA 1.07 · Nylon 1.14 g/cm³.

Resin is even more direct

Resin printing has no infill in the FDM sense: for a solid part, the volume in cm³ is the same number in millilitres of resin. If you hollow the model before slicing, real usage is lower.

Got the G-code? Then estimate nothing

This is the best case and few people use it. After slicing, your slicer already computed everything: walls, top, bottom, supports and brim. That figure is written into comments inside the file itself.

Our calculator reads those comments from PrusaSlicer, Orca, Bambu Studio, Cura, Simplify3D and Slic3r — filling in both the weight and the print time. Bambu users can drop the .gcode.3mf project straight in.

Which format to use

G-code (or .gcode.3mf) — exact, already counts supports and walls. Use it whenever you have it.
3MF — native to Bambu Studio, Orca and PrusaSlicer. Holds multiple parts and plate placement.
STL — the most common in model libraries. Mesh only, no material or scale.
OBJ and PLY — common in modelling and 3D scanning.

The file never leaves your computer

Reading happens inside the browser. Nothing is uploaded to any server, which matters if you handle client models or unreleased projects.

From volume to selling price

Knowing the weight is just the start. Real cost adds material, energy, machine depreciation per hour, consumables, a failure reserve and your labour. Then comes markup — and markup isn't margin: markup is on cost and can exceed 100%; margin is on the selling price and never reaches it. Our calculators show both.