Your workshop. Your data.

Filament cost per gram and remaining spool weight

Divide the price of the filament by its net weight in grams. A 1,000 g spool costing CHF 20 contains filament costing CHF 0.02 per gram. A 750 g spool at the same price costs about CHF 0.0267 per gram. Use the filament weight, not the shipping weight or the weight including its reel.

From spool price to print cost

Print material cost = consumed grams × spool price ÷ net filament grams.

A 120 g print from that CHF 20, 1,000 g spool uses CHF 2.40 of filament. This is material only: electricity, machine allowance, labour, extras and selling costs are separate.

Include what leaves the spool

Count the model, supports and other consumed material. With multiple colours, calculate each material separately at its own price. Check which waste quantities your slicer already includes before adding them again. If a failed attempt consumed 40 g, keep it as a separate run from the successful replacement.

How much filament is left on a spool?

Remaining filament = measured spool-and-filament weight − empty spool weight.

For example, 630 g on the scale minus a 230 g empty reel gives 400 g remaining. Both numbers are illustrative. Remove packaging and loose accessories first. Use the same scale consistently and record when you weighed it.

An empty-spool database can be a starting point, but verify the exact reel version. Cardboard, plastic and refill reels can differ. If the empty weight is uncertain, the remaining filament is also an estimate. A negative result means the weights need checking, not that the spool contains negative filament.

Length is not weight

When an export only supplies filament length, converting it to grams also needs diameter and density. Use the properties of the material actually loaded. BenchTare can complete supported single-material imports from length or volume with explicit filament settings; it does not assume every material has the same density.

Keep inventory separate from predictions

A slicer estimate helps plan the next job. A spool measurement helps correct the stock record. Neither tells you exactly where missing grams went. Record the new remaining amount without inventing a print to explain the difference. BenchTare currently uses manually maintained remaining weights; it does not weigh your spools or deduct inventory through a printer connection.