A fast, accurate tool for anyone who 3D prints and wants to know exactly how much their filament costs per print. Enter the grams your slicer reports, your spool price, and select the material — the calculator shows the material cost instantly, plus cost per gram, cost per metre, and volume consumed.
How it works
The formula has two steps.
Step 1 — cost per gram. Divide the spool price by its net weight in grams. A £22 spool of 1 kg PLA costs £0.022 per gram.
Step 2 — material cost. Multiply cost per gram by the number of grams your slicer reports for the print.
Cost = (spool price ÷ spool weight) × grams used
That is the only arithmetic needed for cost. The calculator also derives two bonus figures that are useful for budgeting and comparing materials:
- Volume used (cm³): mass ÷ density. PLA has a density of 1.24 g/cm³, so 45 g of PLA occupies 45 ÷ 1.24 ≈ 36.3 cm³.
- Length of filament used (m): volume ÷ cross-sectional area of the strand. For 1.75 mm filament the radius is 0.875 mm = 0.0875 cm, giving an area of π × 0.0875² ≈ 0.02405 cm². Dividing 36.3 cm³ by 0.02405 cm² gives roughly 1,510 cm = 15.1 m of strand consumed.
Worked example
A benchy (the iconic calibration boat) typically uses about 13–16 g of PLA on a 0.2 mm layer-height profile. Using a £22 / 1 kg spool:
| Metric | Value |
|---|---|
| Cost per gram | £0.0220 |
| Material cost (15 g) | £0.33 |
| Volume used | 12.1 cm³ |
| Length of filament | ~5.0 m |
| % of spool consumed | 1.5% |
A larger print — say a 200 g structural bracket — costs about £4.40 in PLA at the same spool price. Swapping to PETG (1.27 g/cm³, typically £24 / kg) pushes the bracket cost to about £4.80 — a small premium for better layer adhesion and heat resistance.
Material density reference
Density is a fixed physical property of the polymer; it does not vary by brand (only by fill level). The presets in this calculator use the following values:
| Material | Density (g/cm³) | Notes |
|---|---|---|
| PLA | 1.24 | Most common FDM material |
| PETG | 1.27 | Good all-round, easy to print |
| ABS | 1.04 | Lighter; needs enclosure |
| ASA | 1.07 | UV-stable ABS alternative |
| TPU 95A | 1.21 | Flexible; shore 95A hardness |
| Nylon PA12 | 1.01 | Strong, slightly hygroscopic |
| HIPS | 1.07 | Dissolvable support material |
| PC | 1.20 | Engineering-grade, high temp |
| Carbon-fibre PLA | 1.30 | Composite; stiff, matte finish |
For composite or exotic materials (metal-fill, wood-fill, glow-in-dark), use the Custom option and enter the manufacturer’s stated density, usually found on the technical data sheet or spool label.
Formula note
The length calculation uses the exact cylindrical strand formula. Filament is not perfectly round in practice, but manufacturers specify nominal diameter and tolerance (typically ±0.02–0.05 mm), so the formula agrees closely with slicer estimates. If your slicer gives length directly, you can cross-check: length × π × r² × density should equal the grams figure.
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